Lets Make Rainbows
Creating a web app that displays colored light rays that intersect and blend in a realistic way is possible, although it's worth noting that creating a precise physical simulation of light behavior would be complex. However, we can use simpler models and web technologies to create a visually appealing approximation. Here are some basic steps and technologies you might use:
Canvas API: You'd probably want to use the HTML5 Canvas API to draw the light rays. You can create a canvas that takes up the whole page, and then draw lines or gradients to represent the light rays.
Linear Gradients: You could use linear gradients to represent the light rays. Each ray would start with full opacity on the left side of the page and gradually fade out as it moved towards the center.
Color Blending: As for the color blending, you could use a blending mode to achieve this. In the context of a canvas, globalCompositeOperation property is used to set or return the type of compositing operation to be applied when drawing new shapes. Try using the "lighter" blending mode, which sums the colors of overlapping shapes. It's not a physical simulation of light blending, but it can create a nice visual effect.
Interactivity: If you want to make your app interactive, you could use JavaScript to change the angles or colors of the light rays based on user input. For example, you could let users click and drag to change the direction of the light rays.
Here is a very basic example of how you might start:
html<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
let canvas = document.getElementById('myCanvas');
let ctx = canvas.getContext('2d');
let colors = ['red', 'orange', 'yellow', 'green', 'blue', 'indigo', 'violet'];
ctx.globalCompositeOperation = 'lighter';
for (let i = 0; i < colors.length; i++) {
let grad = ctx.createLinearGradient(0, (i+1)*canvas.height/(colors.length+1), canvas.width/2, canvas.height/2);
grad.addColorStop(0, colors[i]);
grad.addColorStop(1, 'transparent');
ctx.beginPath();
ctx.moveTo(0, (i+1)*canvas.height/(colors.length+1));
ctx.lineTo(canvas.width/2, canvas.height/2);
ctx.strokeStyle = grad;
ctx.lineWidth = 50;
ctx.stroke();
}
</script>
</body>
</html>
In this example, we're creating seven rays of different colors (the colors of the rainbow). Each ray is a line with a linear gradient that fades out towards the center of the page. The colors are added and blended in a way that resembles light mixing thanks to the 'lighter' globalCompositeOperation setting.
This is a simple starting point, and there are many ways you could extend this. For example, you could add more complex user interaction, or create more realistic light effects by implementing a more advanced color blending model.
Yes, it is possible to do ray tracing in a web application, although it's usually more complex and computationally intensive than the simple drawing methods I've described above. Ray tracing is a technique used to create highly realistic lighting and reflections by simulating the path of light rays through a scene.
However, ray tracing usually requires a 3D model to work with, and is generally used for static images or pre-rendered video rather than interactive applications due to its computational intensity. Real-time ray tracing, as seen in modern high-end video games, typically requires specialized hardware (such as RTX GPUs) to perform efficiently.
In terms of how you might implement it in a web application, you'd probably want to use a library or framework that provides some of the necessary functionality. Three.js, for example, is a popular JavaScript library for creating 3D graphics in the browser, and it provides some support for ray tracing.
To note, the Three.js raytracing renderer is not a real-time renderer and is mainly intended for creating high-quality still images or pre-rendered videos.
If you're interested in creating real-time 3D graphics with some of the visual effects you can get from ray tracing (like realistic shadows and reflections), you might want to consider using a technique like ray marching or rasterization with shaders, which can be used to create some similar effects with less computational cost. WebGL (via Three.js or another library) provides the necessary tools for these techniques.
As of my last training cut-off in September 2021, WebGPU was also being developed as a successor to WebGL, and it might provide more advanced functionality for real-time 3D graphics in the future. However, its browser support might still be experimental or under development.
As you're specifically interested in rendering rays of colored light intersecting, a full-blown ray tracer might be overkill. If the Canvas API approach isn't sufficient, a WebGL shader could be a good middle ground. You'd still write code that describes how to calculate the color of each pixel, but it would run on the GPU, giving you much more processing power to work with.
I see, thanks for the clarification. So essentially you are asking for a 2D light simulation where light rays enter a box, bounce around, and eventually intersect or leave the box, much like what might occur in a 2D billiard table.
A simple way to approach this in a 2D space is to treat each "ray" of light as a line segment that can bounce off the walls of your box. When a ray hits a wall, it reflects off at the same angle it hit at (this is the law of reflection).
Here's a very basic pseudocode outline for how you might implement this:
- Start with a list of rays. Each ray has a start point, an angle, and a color.
- For each ray, calculate where it would hit the wall of the box. This is essentially a line-line intersection problem. There are various ways to calculate this, which you can find with a quick search.
- When a ray hits a wall, calculate the angle of reflection and create a new ray starting at the intersection point with the reflected angle and the same color.
- Repeat this process until you've reached a predetermined number of reflections or the rays exit the box.
One point to consider is that you might want to limit the number of reflections, especially if the box is large or the angles lead to a lot of bounces, as this could quickly lead to a lot of rays and slow down your simulation.
To visually represent the rays, you can use a similar approach to the one I described in the previous message, using the HTML Canvas API to draw lines for each ray. You can add alpha blending to the colors to represent the fading of the light over distance or number of bounces.
To simulate the "scattering" effect where the light becomes visible due to dust or particles in the box, you could draw the rays with a certain amount of transparency, so they are visible where they overlap. This is not physically accurate, but it might give a visual effect that is similar to what you're imagining.
This is a fairly simple simulation and won't account for more complex light behaviors like diffraction, polarization, or spectral color mixing, but it might be enough for your purposes, depending on the specifics of your project.
Sure, here is a simple example in JavaScript using an HTML Canvas to display the light rays:
html<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
// Some utilities
function lineIntersection(p0, p1, p2, p3) {
let s1_x, s1_y, s2_x, s2_y;
s1_x = p1.x - p0.x;
s1_y = p1.y - p0.y;
s2_x = p3.x - p2.x;
s2_y = p3.y - p2.y;
let s, t;
s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
return { x: p0.x + (t * s1_x), y: p0.y + (t * s1_y)};
}
return null;
}
function reflect(ray, normal) {
let dot = ray.dx * normal.x + ray.dy * normal.y;
return {
dx: ray.dx - 2 * dot * normal.x,
dy: ray.dy - 2 * dot * normal.y
};
}
// Box definition
let box = [
{ x: 100, y: 100 },
{ x: 700, y: 100 },
{ x: 700, y: 500 },
{ x: 100, y: 500 }
];
// Rays definition
let rays = [
{
x: 0,
y: 200,
dx: 1,
dy: 0,
color: 'red'
},
{
x: 0,
y: 400,
dx: 1,
dy: 0,
color: 'blue'
}
];
let canvas = document.getElementById('myCanvas');
let ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'lighter';
// Draw box
ctx.beginPath();
ctx.moveTo(box[0].x, box[0].y);
for (let i = 1; i < box.length; i++) {
ctx.lineTo(box[i].x, box[i].y);
}
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.stroke();
// Calculate and draw rays
for (let i = 0; i < rays.length; i++) {
let ray = rays[i];
let start = { x: ray.x, y: ray.y };
for (let j = 0; j < 10; j++) { // limit the number of reflections
let closestIntersection = null;
let closestDist = Infinity;
for (let k = 0; k < box.length; k++) {
let p1 = box[k];
let p2 = box[(k+1)%box.length];
let intersection = lineIntersection(start, { x: start.x + ray.dx, y: start.y + ray.dy }, p1, p2);
if (intersection) {
let dx = intersection.x - start.x;
let dy = intersection.y - start.y;
let dist = Math.sqrt(dx*dx + dy*dy);
if (dist < closestDist) {
closestDist = dist;
closestIntersection = intersection;
}
}
}
if (closestIntersection) {
ctx.beginPath();
ctx.moveTo(start.x, start.y);
ctx.lineTo(closestIntersection.x, closestIntersection.y);
ctx.strokeStyle = ray.color;
ctx.stroke();
let normal = {
x: -(closestIntersection.y - start.y),
y: closestIntersection.x - start.x
};
let len = Math.sqrt(normal.x*normal.x + normal.y*normal.y);
normal.x /= len;
normal.y /= len;
ray = reflect(ray, normal);
start = closestIntersection;
} else {
break;
}
}
}
</script>
</body>
</html>
In this example, we start by defining a box and some rays. The box is just a list of points, and each ray has a start point (x, y), a direction vector (dx, dy), and a color.
We then draw the box and calculate and draw the rays. For each ray, we calculate where it intersects the box and draw a line from the start point to the intersection point. We then calculate the reflection of the ray off the wall and move the start point to the intersection point. We repeat this process until the ray leaves the box or we reach a maximum number of reflections.
Note that this is a very simple simulation and does not account for many aspects of real light behavior. It also assumes that the rays are "inside" the box to start with, and does not handle rays that start outside the box. However, it should give you a starting point for a more complex simulation.
I apologize for the confusion. The issue seems to be that the rays do not have their initial positions inside the box. In the current implementation, rays that do not intersect with the box will not be drawn.
Let's update the initial positions of the rays to start from within the box and see if that helps:
javascript// Rays definition
let rays = [
{
x: 150,
y: 200,
dx: 1,
dy: 0,
color: 'red'
},
{
x: 150,
y: 400,
dx: 1,
dy: 0,
color: 'blue'
}
];
Now, the rays should start from within the box and be reflected off the walls.
Please let me know if you have any other questions or encounter any other issues!
I apologize for the confusion. It seems the issue might be due to the calculations for the reflection vectors. Let's try the following:
html<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
// Some utilities
function lineIntersection(p0, p1, p2, p3) {
let s1_x, s1_y, s2_x, s2_y;
s1_x = p1.x - p0.x;
s1_y = p1.y - p0.y;
s2_x = p3.x - p2.x;
s2_y = p3.y - p2.y;
let s, t;
s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
return { x: p0.x + (t * s1_x), y: p0.y + (t * s1_y)};
}
return null;
}
function reflect(ray, normal) {
let dot = ray.dx * normal.x + ray.dy * normal.y;
return {
dx: ray.dx - 2 * dot * normal.x,
dy: ray.dy - 2 * dot * normal.y
};
}
// Box definition
let box = [
{ x: 100, y: 100 },
{ x: 700, y: 100 },
{ x: 700, y: 500 },
{ x: 100, y: 500 }
];
// Rays definition
let rays = [
{
x: 200,
y: 300,
dx: 1,
dy: 0.5,
color: 'red'
},
{
x: 200,
y: 300,
dx: 1,
dy: -0.5,
color: 'blue'
}
];
let canvas = document.getElementById('myCanvas');
let ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'lighter';
// Draw box
ctx.beginPath();
ctx.moveTo(box[0].x, box[0].y);
for (let i = 1; i < box.length; i++) {
ctx.lineTo(box[i].x, box[i].y);
}
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.stroke();
// Calculate and draw rays
for (let i = 0; i < rays.length; i++) {
let ray = rays[i];
let start = { x: ray.x, y: ray.y };
for (let j = 0; j < 10; j++) { // limit the number of reflections
let closestIntersection = null;
let closestDist = Infinity;
for (let k = 0; k < box.length; k++) {
let p1 = box[k];
let p2 = box[(k+1)%box.length];
let intersection = lineIntersection(start, { x: start.x + ray.dx*1000, y: start.y + ray.dy*1000 }, p1, p2);
if (intersection) {
let dx = intersection.x - start.x;
let dy = intersection.y - start.y;
let dist = Math.sqrt(dx*dx + dy*dy);
if (dist < closestDist) {
closestDist = dist;
closestIntersection = intersection;
}
}
}
if (closestIntersection) {
ctx.beginPath();
ctx.moveTo(start.x, start.y);
ctx.lineTo(closestIntersection.x, closestIntersection.y);
ctx.strokeStyle = ray.color;
ctx.stroke();
let dx = closestIntersection.x - start.x;
let dy = closestIntersection.y - start.y;
let len = Math.sqrt(dx*dx + dy*dy);
dx /= len;
dy /= len;
ray = reflect({dx: dx, dy: dy}, {x: -dy, y: dx});
start = closestIntersection;
} else {
break;
}
}
}
</script>
</body>
</html>
In this version, we've also added a multiplier to the dx and dy values inside the lineIntersection function to ensure the ray extends to the box's boundaries. Please let me know if this works for you!
I apologize for the confusion and thank you for your patience. The issue appears to be in the reflect function, where the normal vector isn't correctly calculated.
We're incorrectly calculating the normal as the perpendicular vector of the vector from the start to the intersection point. Instead, we should be calculating the normal as the perpendicular vector of the box wall that the ray intersects with.
Here's the corrected version:
html<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
// Some utilities
function lineIntersection(p0, p1, p2, p3) {
let s1_x, s1_y, s2_x, s2_y;
s1_x = p1.x - p0.x;
s1_y = p1.y - p0.y;
s2_x = p3.x - p2.x;
s2_y = p3.y - p2.y;
let s, t;
s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
return { x: p0.x + (t * s1_x), y: p0.y + (t * s1_y)};
}
return null;
}
function reflect(ix, iy, nx, ny) {
// Compute the dot product of the input vector and the normal
let dot = ix*nx + iy*ny;
// Compute the projection of the input vector onto the normal
let px = dot * nx;
let py = dot * ny;
// Subtract the projection twice to compute the reflection
return {dx: ix - 2*px, dy: iy - 2*py};
}
// Box definition
let box = [
{ x: 100, y: 100 },
{ x: 700, y: 100 },
{ x: 700, y: 500 },
{ x: 100, y: 500 }
];
// Rays definition
let rays = [
{
x: 200,
y: 300,
dx: 1,
dy: 0.5,
color: 'red'
},
{
x: 200,
y: 300,
dx: 1,
dy: -0.5,
color: 'blue'
}
];
let canvas = document.getElementById('myCanvas');
let ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'lighter';
// Draw box
ctx.beginPath();
ctx.moveTo(box[0].x, box[0].y);
for (let i = 1; i < box.length; i++) {
ctx.lineTo(box[i].x, box[i].y);
}
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.stroke();
// Calculate and draw rays
for (let i = 0; i < rays.length; i++) {
let ray = rays[i];
let start = { x: ray.x, y: ray.y };
for (let j = 0; j < 10; j++) { // limit the number of reflections
let closestIntersection = null;
let closestDist = Infinity;
let closestNormal = null;
for (let k = 0; k < box.length; k++) {
let p1 = box[k];
let p2 = box[(k+1)%box.length];
let intersection = lineIntersection(start, { x: start.x + ray.dx*1000, y: start.y + ray.dy*1000 }, p1, p2);
if (intersection) {
let dx = intersection.x - start.x;
let dy = intersection.y - start.y;
let dist = Math.sqrt(dx*dx + dy*dy);
if (dist < closestDist) {
closestDist = dist;
closestIntersection = intersection;
// Calculate the normal at the intersection point
let nx = -(p2.y - p1.y);
let ny = p2.x - p1.x;
let nLen = Math.sqrt(nx*nx + ny*ny);
closestNormal = {x: nx/nLen, y: ny/nLen};
}
}
}
if (closestIntersection) {
ctx.beginPath();
ctx.moveTo(start.x, start.y);
ctx.lineTo(closestIntersection.x, closestIntersection.y);
ctx.strokeStyle = ray.color;
ctx.stroke();
let reflection = reflect(ray.dx, ray.dy, closestNormal.x, closestNormal.y);
ray = {dx: reflection.dx, dy: reflection.dy, color: ray.color};
start = closestIntersection;
} else {
break;
}
}
}
</script>
</body>
</html>
I hope this is more in line with what you're looking for. Please let me know if you have any other questions or encounter any other issues!
I'm sorry for the inconvenience. It seems there was a mistake in the reflect function where we were not correctly inverting the dot product calculation. Also, let's modify the conditions to ensure the rays only reflect off the walls of the box and don't "tunnel" through them due to the distance calculation. Here's the corrected version:
html<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
// Some utilities
function lineIntersection(p0, p1, p2, p3) {
let s1_x, s1_y, s2_x, s2_y;
s1_x = p1.x - p0.x;
s1_y = p1.y - p0.y;
s2_x = p3.x - p2.x;
s2_y = p3.y - p2.y;
let s, t;
s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
return { x: p0.x + (t * s1_x), y: p0.y + (t * s1_y)};
}
return null;
}
function reflect(ix, iy, nx, ny) {
// Compute the dot product of the input vector and the normal
let dot = ix*nx + iy*ny;
// Compute the projection of the input vector onto the normal
let px = dot * nx;
let py = dot * ny;
// Subtract the projection twice to compute the reflection
return {dx: ix - 2*px, dy: iy - 2*py};
}
// Box definition
let box = [
{ x: 100, y: 100 },
{ x: 700, y: 100 },
{ x: 700, y: 500 },
{ x: 100, y: 500 }
];
// Rays definition
let rays = [
{
x: 200,
y: 300,
dx: 1,
dy: 0.5,
color: 'red'
},
{
x: 200,
y: 300,
dx: 1,
dy: -0.5,
color: 'blue'
}
];
let canvas = document.getElementById('myCanvas');
let ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'lighter';
// Draw box
ctx.beginPath();
ctx.moveTo(box[0].x, box[0].y);
for (let i = 1; i < box.length; i++) {
ctx.lineTo(box[i].x, box[i].y);
}
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.stroke();
// Calculate and draw rays
for (let i = 0; i < rays.length; i++) {
let ray = rays[i];
let start = { x: ray.x, y: ray.y };
for (let j = 0; j < 10; j++) { // limit the number of reflections
let closestIntersection = null;
let closestDist = Infinity;
let closestNormal = null;
for (let k = 0; k < box.length; k++) {
let p1 = box[k];
let p2 = box[(k+1)%box.length];
let intersection = lineIntersection(start, { x: start.x + ray.dx*1000, y: start.y + ray.dy*1000 }, p1, p2);
if (intersection) {
let dx = intersection.x - start.x;
let dy = intersection.y - start.y;
let dist = Math.sqrt(dx*dx + dy*dy);
if (dist < closestDist) {
closestDist = dist;
closestIntersection = intersection;
// Calculate the normal at the intersection point
let nx = -(p2.y - p1.y);
let ny = p2.x - p1.x;
let nLen = Math.sqrt(nx*nx + ny*ny);
closestNormal = {x: nx/nLen, y: ny/nLen};
}
}
}
if (closestIntersection && closestDist < 1000) {
ctx.beginPath();
ctx.moveTo(start.x, start.y);
ctx.lineTo(closestIntersection.x, closestIntersection.y);
ctx.strokeStyle = ray.color;
ctx.stroke();
let reflection = reflect(ray.dx, ray.dy, closestNormal.x, closestNormal.y);
ray = {dx: reflection.dx, dy: reflection.dy, color: ray.color};
start = closestIntersection;
} else {
break;
}
}
}
</script>
</body>
</html>
This should create the correct ray reflections within the box. Please try again and let me know if this solves the issue.
I apologize for the confusion earlier. It appears that there was indeed an issue with the reflection calculation. Let's fix this. The mistake was that we didn't correctly take into account the dot product being negative when the incident ray is pointing away from the normal.
Here's the corrected version:
html<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.
</canvas>
<script>
// Some utilities
function lineIntersection(p0, p1, p2, p3) {
let s1_x, s1_y, s2_x, s2_y;
s1_x = p1.x - p0.x;
s1_y = p1.y - p0.y;
s2_x = p3.x - p2.x;
s2_y = p3.y - p2.y;
let s, t;
s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
return { x: p0.x + (t * s1_x), y: p0.y + (t * s1_y)};
}
return null;
}
function reflect(ix, iy, nx, ny) {
// Compute the dot product of the input vector and the normal
let dot = ix*nx + iy*ny;
// Compute the projection of the input vector onto the normal
let px = 2 * dot * nx;
let py = 2 * dot * ny;
// Subtract the projection from the input vector to get the reflection
return {dx: ix - px, dy: iy - py};
}
// Box definition
let box = [
{ x: 100, y: 100 },
{ x: 700, y: 100 },
{ x: 700, y: 500 },
{ x: 100, y: 500 }
];
// Rays definition
let rays = [
{
x: 200,
y: 300,
dx: 1,
dy: 0.5,
color: 'red'
},
{
x: 200,
y: 300,
dx: 1,
dy: -0.5,
color: 'blue'
}
];
let canvas = document.getElementById('myCanvas');
let ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'lighter';
// Draw box
ctx.beginPath();
ctx.moveTo(box[0].x, box[0].y);
for (let i = 1; i < box.length; i++) {
ctx.lineTo(box[i].x, box[i].y);
}
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.stroke();
// Calculate and draw rays
for (let i = 0; i < rays.length; i++) {
let ray = rays[i];
let start = { x: ray.x, y: ray.y };
for (let j = 0; j < 10; j++) { // limit the number of reflections
let closestIntersection = null;
let closestDist = Infinity;
let closestNormal = null;
for (let k = 0; k < box.length; k++) {
let p1 = box[k];
let p2 = box[(k+1)%box.length];
let intersection = lineIntersection(start, { x: start.x + ray.dx*1000, y: start.y + ray.dy*1000 }, p1, p2);
if (intersection) {
let dx = intersection.x - start.x;
let dy = intersection.y - start.y;
let dist = Math.sqrt(dx*dx + dy*dy);
if (dist < closestDist) {
closestDist = dist;
closestIntersection = intersection;
// Calculate the normal at the intersection point
let nx = -(p2.y - p1.y);
let ny = p2.x - p1.x;
let nLen = Math.sqrt(nx*nx + ny*ny);
closestNormal = {x: nx/nLen, y: ny/nLen};
}
}
}
if (closestIntersection) {
ctx.beginPath();
ctx.moveTo(start.x, start.y);
ctx.lineTo(closestIntersection.x, closestIntersection.y);
ctx.strokeStyle = ray.color;
ctx.stroke();
let reflection = reflect(ray.dx, ray.dy, closestNormal.x, closestNormal.y);
ray = {dx: reflection.dx, dy: reflection.dy, color: ray.color};
start = closestIntersection;
} else {
break;
}
}
}
</script>
</body>
</html>
I'm confident this should create the correct ray reflections within the box. Please let me know if this resolves the issue.
Yes, Three.js can be used to create a 3D visualization of rays of light bouncing around, but keep in mind that it's not a full ray tracing engine like you might find in more robust graphics software. It's primarily a rasterization engine, which means it can quickly and efficiently draw 3D objects, but doesn't by default support the kind of physical light simulation that ray tracing implies.
That being said, you can implement basic ray tracing techniques in Three.js. Instead of dealing with pixel colors directly, as you might in a full ray tracing engine, you would deal with geometries and materials.
Here's a very basic example of how you might use Three.js to create rays of light that bounce off surfaces:
javascriptconst scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
const geometry = new THREE.BoxGeometry(1, 1, 1);
const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);
camera.position.z = 5;
const animate = function () {
requestAnimationFrame(animate);
cube.rotation.x += 0.01;
cube.rotation.y += 0.01;
renderer.render(scene, camera);
};
animate();
// Define the raycaster
const raycaster = new THREE.Raycaster();
// Define a Vector3 to represent the direction of the ray
const direction = new THREE.Vector3(1, 0, 0);
// Each frame, set the raycaster's ray to point in the direction the cube is rotating
raycaster.set(cube.position, direction);
// Check if the ray intersects any objects in the scene
const intersects = raycaster.intersectObjects(scene.children);
// If the ray intersects any objects, reflect the ray off the surface of the first object it intersects
if (intersects.length > 0) {
direction.reflect(intersects[0].face.normal);
}
This code simply creates a scene with a rotating cube, and a ray that starts at the position of the cube and points in the x direction. If the ray hits any objects in the scene (including the cube itself), it calculates the reflection of the ray off the surface of the object.
This is a simplified example and does not include the simulation of light colors or the handling of multiple rays. However, it should give you a starting point for understanding how to work with rays in Three.js.
For more complex light simulation and ray tracing, you might want to consider using a full-featured graphics engine or ray tracing library. WebGL, which Three.js is built on, also has limitations in terms of the complexity and performance of ray tracing that can be achieved, especially compared to more powerful APIs like Vulkan or DirectX.
Sure, we can definitely integrate the JavaScript code into HTML format. Here's an example of how you can do it. Please note that you'll need to include the three.js library in your project to make this work. You can do so by adding a script tag pointing to the library's URL:
html<!DOCTYPE html>
<html>
<head>
<title>My first three.js app</title>
<style>
body { margin: 0; }
canvas { display: block; }
</style>
</head>
<body>
<script src="https://threejs.org/build/three.js"></script>
<script>
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
const geometry = new THREE.BoxGeometry(1, 1, 1);
const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);
camera.position.z = 5;
const animate = function () {
requestAnimationFrame(animate);
cube.rotation.x += 0.01;
cube.rotation.y += 0.01;
// Define the raycaster
const raycaster = new THREE.Raycaster();
// Define a Vector3 to represent the direction of the ray
const direction = new THREE.Vector3(1, 0, 0);
// Each frame, set the raycaster's ray to point in the direction the cube is rotating
raycaster.set(cube.position, direction);
// Check if the ray intersects any objects in the scene
const intersects = raycaster.intersectObjects(scene.children);
// If the ray intersects any objects, reflect the ray off the surface of the first object it intersects
if (intersects.length > 0) {
direction.reflect(intersects[0].face.normal);
}
renderer.render(scene, camera);
};
animate();
</script>
</body>
</html>
Remember to serve your HTML file from a server (either local or online) because three.js will have issues loading from a local file system due to browser restrictions.
My apologies for the confusion. While the raycaster and reflection logic are functioning in the script, we aren't visualizing these rays in any way. The Raycaster object in Three.js is commonly used for detecting intersections between rays and other objects, such as for mouse picking (determining what object the mouse is over) or simple collision detection. It doesn't inherently provide a way to visualize rays.
For simplicity and visualization purposes, I'd suggest creating a thin CylinderGeometry object along the direction of the ray when an intersection is found. However, it's worth noting that this won't be exactly raytracing and doesn't account for light color and other factors as a real raytracing would.
Here's a simplified modification of the previous code that adds a line to the scene to represent the ray:
html<!DOCTYPE html>
<html>
<head>
<title>My first three.js app</title>
<style>
body { margin: 0; }
canvas { display: block; }
</style>
</head>
<body>
<script src="https://threejs.org/build/three.js"></script>
<script>
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
const geometry = new THREE.BoxGeometry(1, 1, 1);
const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);
camera.position.z = 5;
const animate = function () {
requestAnimationFrame(animate);
cube.rotation.x += 0.01;
cube.rotation.y += 0.01;
// Define the raycaster
const raycaster = new THREE.Raycaster();
// Define a Vector3 to represent the direction of the ray
const direction = new THREE.Vector3(1, 0, 0);
// Each frame, set the raycaster's ray to point in the direction the cube is rotating
raycaster.set(cube.position, direction);
// Check if the ray intersects any objects in the scene
const intersects = raycaster.intersectObjects(scene.children);
// If the ray intersects any objects, reflect the ray off the surface of the first object it intersects
if (intersects.length > 0) {
direction.reflect(intersects[0].face.normal);
// Create a line to represent the ray
const lineGeometry = new THREE.Geometry();
lineGeometry.vertices.push(
new THREE.Vector3(cube.position.x, cube.position.y, cube.position.z),
new THREE.Vector3(intersects[0].point.x, intersects[0].point.y, intersects[0].point.z)
);
const lineMaterial = new THREE.LineBasicMaterial({ color: 0xff0000 });
const line = new THREE.Line(lineGeometry, lineMaterial);
scene.add(line);
}
renderer.render(scene, camera);
};
animate();
</script>
</body>
</html>
Remember, this is a simple and illustrative example of raycasting and won't give you the full functionalities of a proper raytracer. Developing a full-fledged raytracer involves more complex topics like lighting, shadows, reflections, and refractions, which go beyond the scope of this example.
Apologies for the confusion. The code was indeed flawed as it attempted to create and draw a line within the animation loop but, due to the location of the code and the continuously rotating cube, it was unlikely to create the line.
We need to move the raycasting out of the animation loop, and into a standalone function. We can then call this function whenever we want to create a ray. Here's a corrected version of the code:
html<!DOCTYPE html>
<html>
<head>
<title>My first three.js app</title>
<style>
body { margin: 0; }
canvas { display: block; }
</style>
</head>
<body>
<script src="https://threejs.org/build/three.js"></script>
<script>
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
const geometry = new THREE.BoxGeometry(1, 1, 1);
const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);
camera.position.z = 5;
// Define the raycaster
const raycaster = new THREE.Raycaster();
// Define a Vector3 to represent the direction of the ray
const direction = new THREE.Vector3(1, 0, 0);
function castRay() {
// Set the raycaster's ray to point in the direction the cube is rotating
raycaster.set(cube.position, direction);
// Check if the ray intersects any objects in the scene
const intersects = raycaster.intersectObjects(scene.children);
// If the ray intersects any objects, reflect the ray off the surface of the first object it intersects
if (intersects.length > 0) {
direction.reflect(intersects[0].face.normal);
// Create a line to represent the ray
const lineGeometry = new THREE.Geometry();
lineGeometry.vertices.push(
new THREE.Vector3(cube.position.x, cube.position.y, cube.position.z),
new THREE.Vector3(intersects[0].point.x, intersects[0].point.y, intersects[0].point.z)
);
const lineMaterial = new THREE.LineBasicMaterial({ color: 0xff0000 });
const line = new THREE.Line(lineGeometry, lineMaterial);
scene.add(line);
}
}
const animate = function () {
requestAnimationFrame(animate);
cube.rotation.x += 0.01;
cube.rotation.y += 0.01;
renderer.render(scene, camera);
};
animate();
castRay();
</script>
</body>
</html>
In this version of the code, we've moved the raycasting into its own function, castRay(), and call it once after we start the animation loop with animate(). This will add a line representing the ray to the scene at the start of the program.
If you want to continuously cast rays, you could call castRay() within the animation loop, but keep in mind that each raycast adds a new line to the scene, which could quickly clutter the scene and slow down the performance of the program. You might want to consider removing or hiding previous lines if you decide to cast rays in a loop.
Please try this and see if it works for you.
I apologize for the confusion. It appears there was an oversight. In the context of a single cube rotating in the scene, the ray would rarely intersect because it's being cast from the cube's center outward. Here's a simplified example where we use a plane to reliably generate an intersection and show a line to represent the ray:
html<!DOCTYPE html>
<html>
<head>
<title>Raycaster Example</title>
<style>
body { margin: 0; }
canvas { display: block; }
</style>
</head>
<body>
<script src="https://threejs.org/build/three.js"></script>
<script>
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
// Create a plane that will intersect with our ray
const planeGeometry = new THREE.PlaneGeometry(5, 5);
const planeMaterial = new THREE.MeshBasicMaterial({ color: 0x00ff00, side: THREE.DoubleSide });
const plane = new THREE.Mesh(planeGeometry, planeMaterial);
scene.add(plane);
camera.position.z = 5;
// Define the raycaster
const raycaster = new THREE.Raycaster();
// Define a Vector3 to represent the direction of the ray
const direction = new THREE.Vector3(0, 0, -1);
function castRay() {
// Set the raycaster's ray to start from the camera and go forward
raycaster.set(camera.position, direction);
// Check if the ray intersects any objects in the scene
const intersects = raycaster.intersectObjects(scene.children);
// If the ray intersects any objects, draw a line from the camera to the intersection point
if (intersects.length > 0) {
const lineGeometry = new THREE.Geometry();
lineGeometry.vertices.push(
new THREE.Vector3(camera.position.x, camera.position.y, camera.position.z),
new THREE.Vector3(intersects[0].point.x, intersects[0].point.y, intersects[0].point.z)
);
const lineMaterial = new THREE.LineBasicMaterial({ color: 0xff0000 });
const line = new THREE.Line(lineGeometry, lineMaterial);
scene.add(line);
}
}
const animate = function () {
requestAnimationFrame(animate);
renderer.render(scene, camera);
};
animate();
castRay();
</script>
</body>
</html>
This code will create a red line extending from the camera position to the center of the green plane in the scene, representing a raycast from the camera. This is a very basic example, but it shows how you can use raycasting to detect intersections in Three.js.
If you want the rays to emanate from a specific source (other than the camera) and reflect, more work is needed, and you'd have to calculate the reflection vectors manually. Also remember, that while Three.js is a powerful library, it's not fully designed to simulate the physical properties of light, like ray tracing engines do. It is instead designed to provide a simple and efficient way to create 3D graphics in the browser.
I apologize for the confusion. As of the release of three.js r125 in December 2020, the Geometry class, which was used to create custom geometry, has been removed in favor of the BufferGeometry class. Please use the following code which uses BufferGeometry and Line classes for creating lines.
html<!DOCTYPE html>
<html>
<head>
<title>Raycaster Example</title>
<style>
body { margin: 0; }
canvas { display: block; }
</style>
</head>
<body>
<script src="https://threejs.org/build/three.js"></script>
<script>
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
// Create a plane that will intersect with our ray
const planeGeometry = new THREE.PlaneGeometry(5, 5);
const planeMaterial = new THREE.MeshBasicMaterial({ color: 0x00ff00, side: THREE.DoubleSide });
const plane = new THREE.Mesh(planeGeometry, planeMaterial);
scene.add(plane);
camera.position.z = 5;
// Define the raycaster
const raycaster = new THREE.Raycaster();
// Define a Vector3 to represent the direction of the ray
const direction = new THREE.Vector3(0, 0, -1);
function castRay() {
// Set the raycaster's ray to start from the camera and go forward
raycaster.set(camera.position, direction);
// Check if the ray intersects any objects in the scene
const intersects = raycaster.intersectObjects(scene.children);
// If the ray intersects any objects, draw a line from the camera to the intersection point
if (intersects.length > 0) {
const points = [];
points.push(new THREE.Vector3(camera.position.x, camera.position.y, camera.position.z));
points.push(new THREE.Vector3(intersects[0].point.x, intersects[0].point.y, intersects[0].point.z));
const lineGeometry = new THREE.BufferGeometry().setFromPoints(points);
const lineMaterial = new THREE.LineBasicMaterial({ color: 0xff0000 });
const line = new THREE.Line(lineGeometry, lineMaterial);
scene.add(line);
}
}
const animate = function () {
requestAnimationFrame(animate);
renderer.render(scene, camera);
};
animate();
castRay();
</script>
</body>
</html>
This example should now work as expected with three.js version r125 and later. This will display a plane and a line showing the ray intersecting with the plane.
I'm sorry for any frustration. Indeed, if the goal is to create more complex light interactions including color blending and reflections, a pure 3D rendering library like three.js might not be the optimal solution. As mentioned, ray tracing would be ideal for this, but it's quite complex to implement from scratch and may not be performant in a web browser environment.
You may want to explore other options such as:
Shader programming: WebGL and libraries like three.js allow for custom shader programming, which is essentially a way to program the GPU directly. This can allow for more complex and performant light effects, but requires knowledge of GLSL (the shader language) and GPU programming concepts.
2D canvas API: If the desired effects can be simplified to 2D, the built-in HTML5 canvas API allows for pixel-level manipulation, which can be used to create various light effects. This would likely be more performant than a 3D approach but may not achieve the same level of realism.
Pre-rendered images: Depending on your exact needs, you may be able to achieve the desired effect by pre-rendering images (or sequences of images) with a tool like Blender, then displaying those images in the browser.
I hope these alternative solutions can be helpful. I'm here to provide more guidance if you need further clarification or help on these topics.
Yes, using a particle system in p5.js to simulate the path and behavior of light particles can be a valid and creative approach to visualizing color interactions and reflections. P5.js is particularly suited for 2D graphics and would provide the necessary tools for pixel-level manipulation and color blending.
Your approach seems plausible. You would essentially be simulating a very simplified version of ray tracing, where each particle represents a 'ray' of light that can interact with other particles and change direction when it hits certain objects.
Creating such a system involves several steps:
Creating the particles: The particles can be objects that have properties for position, velocity, and color.
Drawing the particles: Each frame, draw a line or dot at the particle's position, using its color.
Moving the particles: Update the particles' positions based on their velocities.
Checking for overlap: When drawing each particle, check if its current position overlaps with any other particles. If it does, mix the colors based on a formula of your choice.
Handling reflections: When a particle hits a wall, reflect it by inverting its velocity.
Handling refractions: If a particle is inside a refracting material, change its direction based on the color and a defined refraction index.
While this approach should be feasible, it may also be quite performance intensive if there are a lot of particles or if the canvas size is large, since you need to check for overlap between every pair of particles. There are ways to optimize this, for instance by dividing the canvas into a grid and only checking for overlaps within each cell. However, implementing these optimizations might be complex.
Remember, this won't be physically accurate and is a simplified simulation of how light behaves. However, it should be sufficient for creating interesting visual effects and demonstrating the basic principles of color mixing and light refraction.
Would you like help starting to implement this in p5.js?
I see what you're saying, and yes, you're correct. We could modify the pixels as each particle moves across the canvas. When a particle passes over a pixel, we could mix the particle's color with the existing color of that pixel.
Here's a simple demonstration of the basic idea, where we have 3 particles with primary colors (red, green, blue) that move across the canvas and color the pixels they pass over. When two or more particles overlap on the same pixel, their colors will mix.
html<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.js"></script>
<style> body {padding: 30px;} </style>
</head>
<body>
<script>
let particles = [];
let d = 1; // direction of movement
function setup() {
createCanvas(710, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles.push(new Particle(100, 200, color(255, 0, 0, 100)));
particles.push(new Particle(100, 210, color(0, 255, 0, 100)));
particles.push(new Particle(100, 220, color(0, 0, 255, 100)));
}
function draw() {
particles.forEach(particle => {
particle.move();
particle.display();
});
}
class Particle {
constructor(x, y, c) {
this.x = x;
this.y = y;
this.c = c;
}
move() {
this.x = this.x + d;
if(this.x >= width) d = -1;
if(this.x <= 0) d = 1;
}
display() {
noStroke();
fill(this.c);
rect(this.x, this.y, 1, 1);
}
}
</script>
</body>
</html>
This script creates a 2D space with 3 moving particles. Each particle leaves a colored trace in its path. When particles cross paths, their colors are combined.
Note that the colorMode() function is set to (RGB, 255, 255, 255, 100) to allow color mixing using the alpha channel. The '100' in this line sets the maximum alpha value to 100, allowing semi-transparency. This will make overlapping colors mix.
This code uses a simple rect() function to represent particles and color the pixels. It's just an initial demo. We can enhance it by adding more particles, colors, bounce effect on hitting the wall, etc. Please let me know if this is along the lines of what you're thinking, and if there are other features you'd like to see implemented!
I'm thrilled to hear that you're happy with this approach! It's a creative way to visualize light behavior and color mixing, and I'm glad you find it exciting.
Now that we have the basic setup with particles coloring the pixels and the colors mixing when the particles overlap, we can start to think about other features you might want to add:
Refraction: You could create zones on the canvas that cause particles to change their direction of movement. The change in direction could be color-dependent, simulating how different wavelengths of light refract at different angles.
More colors: Right now, we're only using three primary colors. You could add more particles with different colors to create a more diverse and vivid color mix.
Particle interaction: Rather than just having particles move in a straight line, you could create some interaction between the particles, making them attract or repel each other, for example.
User interaction: You could allow the user to add particles by clicking or dragging the mouse, change the direction of particles, or manipulate other aspects of the simulation.
Please let me know if you'd like help implementing any of these ideas, or if there are other features you're interested in!
Alright, let's modify the move method in our Particle class so that the particles "bounce" when they hit the edges of the canvas.
To do this, we'll check if the particle's x or y position has gone outside the canvas dimensions, and if so, we'll invert the direction of their movement. Here's how we can do it:
html<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.js"></script>
<style> body {padding: 30px;} </style>
</head>
<body>
<script>
let particles = [];
let dx = 1; // x direction of movement
let dy = 0.5; // y direction of movement
function setup() {
createCanvas(710, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles.push(new Particle(100, 200, color(255, 0, 0, 100)));
particles.push(new Particle(100, 210, color(0, 255, 0, 100)));
particles.push(new Particle(100, 220, color(0, 0, 255, 100)));
}
function draw() {
particles.forEach(particle => {
particle.move();
particle.display();
});
}
class Particle {
constructor(x, y, c) {
this.x = x;
this.y = y;
this.c = c;
}
move() {
if (this.x + dx > width || this.x + dx < 0) dx = -dx;
if (this.y + dy > height || this.y + dy < 0) dy = -dy;
this.x = this.x + dx;
this.y = this.y + dy;
}
display() {
noStroke();
fill(this.c);
rect(this.x, this.y, 1, 1);
}
}
</script>
</body>
</html>
In this code, we added dy to simulate movement in the y-direction and updated the move function to bounce the particles when they hit the boundaries. With this update, particles should now bounce off the walls and change direction when they hit the edge of the canvas.
You're absolutely right, and it's a great observation! In physics-based simulations, such issues, known as "tunneling", can indeed occur when the time step is too large or the speed is too high. In these situations, a particle might move more than the distance to the wall in one step, ending up on the wrong side of the wall.
One common way to prevent this is to use a concept of a particle's "size" or "radius". When checking for collisions, you don't check the particle's center point, but you take into account the radius, and check if the particle's edge would hit the wall. If it would, you place the particle next to the wall, not beyond it.
Let's introduce a "radius" for our particles and modify our move function accordingly. In this context, the radius won't physically make the particle larger, but it will be used to prevent the particle from ending up outside of the canvas.
Here's how we can update our code:
html<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.js"></script>
<style> body {padding: 30px;} </style>
</head>
<body>
<script>
let particles = [];
let dx = 1; // x direction of movement
let dy = 0.5; // y direction of movement
function setup() {
createCanvas(710, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles.push(new Particle(100, 200, color(255, 0, 0, 100), 1));
particles.push(new Particle(100, 210, color(0, 255, 0, 100), 1));
particles.push(new Particle(100, 220, color(0, 0, 255, 100), 1));
}
function draw() {
particles.forEach(particle => {
particle.move();
particle.display();
});
}
class Particle {
constructor(x, y, c, r) {
this.x = x;
this.y = y;
this.c = c;
this.r = r;
}
move() {
if (this.x + dx + this.r > width || this.x + dx - this.r < 0) dx = -dx;
if (this.y + dy + this.r > height || this.y + dy - this.r < 0) dy = -dy;
this.x = this.x + dx;
this.y = this.y + dy;
}
display() {
noStroke();
fill(this.c);
rect(this.x, this.y, 1, 1);
}
}
</script>
</body>
</html>
In this code, I introduced a new parameter r for radius in the Particle class. The move method now takes the particle's radius into account when checking if it's about to hit a wall. This should ensure that no matter how fast the particles are moving, they should never end up outside of the canvas.
Using circles to represent photons is more visually accurate and pleasing because light particles, or photons, are usually represented as points or circles in 2D visualizations. Rectangles might give the impression of directionality or orientation, which isn't accurate for photons.
That said, using circles could be computationally more expensive. Drawing a rectangle is cheaper in terms of computing resources because it only requires four points (the vertices), while a circle requires many more to look smooth.
However, given the scale and complexity of this particular project, the difference is unlikely to be noticeable, so it would be totally fine to use circles. Here's how to do that:
html<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.js"></script>
<style> body {padding: 30px;} </style>
</head>
<body>
<script>
let particles = [];
let dx = 1; // x direction of movement
let dy = 0.5; // y direction of movement
function setup() {
createCanvas(710, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles.push(new Particle(100, 200, color(255, 0, 0, 100), 2));
particles.push(new Particle(100, 210, color(0, 255, 0, 100), 2));
particles.push(new Particle(100, 220, color(0, 0, 255, 100), 2));
}
function draw() {
particles.forEach(particle => {
particle.move();
particle.display();
});
}
class Particle {
constructor(x, y, c, r) {
this.x = x;
this.y = y;
this.c = c;
this.r = r;
}
move() {
if (this.x + dx + this.r > width || this.x + dx - this.r < 0) dx = -dx;
if (this.y + dy + this.r > height || this.y + dy - this.r < 0) dy = -dy;
this.x = this.x + dx;
this.y = this.y + dy;
}
display() {
noStroke();
fill(this.c);
ellipse(this.x, this.y, this.r * 2, this.r * 2);
}
}
</script>
</body>
</html>
In this code, I simply replaced rect() with ellipse() in the display() method, and increased the radius to 2 in the particle creation to make the circles more visible. The arguments for ellipse() are the x and y coordinates of the center, and the width and height of the ellipse. Since we want a circle, the width and height are both r * 2. The particles are now drawn as circles.
That's an interesting observation and it seems like an unintended effect caused by a design detail in our implementation. Currently, all particles share the same dx and dy for their movement. When one particle hits the wall and reverses the direction by setting dy = -dy, it changes the direction for all particles.
To resolve this, we should assign each particle its own dx and dy. Here's the revised code:
html<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.js"></script>
<style> body {padding: 30px;} </style>
</head>
<body>
<script>
let particles = [];
function setup() {
createCanvas(710, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles.push(new Particle(100, 200, color(255, 0, 0, 100), 2, 1, 0.5));
particles.push(new Particle(100, 210, color(0, 255, 0, 100), 2, 1, 0.4));
particles.push(new Particle(100, 220, color(0, 0, 255, 100), 2, 1, 0.6));
}
function draw() {
particles.forEach(particle => {
particle.move();
particle.display();
});
}
class Particle {
constructor(x, y, c, r, dx, dy) {
this.x = x;
this.y = y;
this.c = c;
this.r = r;
this.dx = dx; // Each particle now has its own dx
this.dy = dy; // Each particle now has its own dy
}
move() {
if (this.x + this.dx + this.r > width || this.x + this.dx - this.r < 0) this.dx = -this.dx;
if (this.y + this.dy + this.r > height || this.y + this.dy - this.r < 0) this.dy = -this.dy;
this.x = this.x + this.dx;
this.y = this.y + this.dy;
}
display() {
noStroke();
fill(this.c);
ellipse(this.x, this.y, this.r * 2, this.r * 2);
}
}
</script>
</body>
</html>
Now, each particle has its own dx and dy parameters which will cause them to bounce off the edges independently. I also slightly varied the dy values to give each particle a unique angle.
Absolutely! Using vectors to represent velocities can provide more flexibility and makes it easier to perform various operations like addition, subtraction, scaling, and rotation. In addition, checking for wall collisions as per the above code can help to prevent the particles from getting stuck in the wall.
Here's how you might revise our code to incorporate these concepts:
html<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.js"></script>
<style> body {padding: 30px;} </style>
</head>
<body>
<script>
let particles = [];
function setup() {
createCanvas(710, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles.push(new Particle(createVector(100, 200), createVector(2, 1), color(255, 0, 0, 100), 10));
particles.push(new Particle(createVector(100, 210), createVector(2, 0.8), color(0, 255, 0, 100), 10));
particles.push(new Particle(createVector(100, 220), createVector(2, 1.2), color(0, 0, 255, 100), 10));
}
function draw() {
particles.forEach(particle => {
particle.move();
particle.display();
});
}
class Particle {
constructor(position, velocity, c, r) {
this.position = position;
this.velocity = velocity;
this.c = c;
this.r = r;
}
move() {
this.position.add(this.velocity);
this.checkWalls();
}
checkWalls() {
if (this.position.x + this.r > width || this.position.x - this.r < 0) {
this.velocity.x *= -1;
this.position.x = constrain(this.position.x, this.r, width - this.r);
}
if (this.position.y + this.r > height || this.position.y - this.r < 0) {
this.velocity.y *= -1;
this.position.y = constrain(this.position.y, this.r, height - this.r);
}
}
display() {
noStroke();
fill(this.c);
ellipse(this.position.x, this.position.y, this.r * 2, this.r * 2);
}
}
</script>
</body>
</html>
This code does the following:
- Uses the p5.Vector to represent the particle's position and velocity. This allows us to leverage various vector operations provided by p5.js.
- Incorporates a
checkWalls()method in theParticleclass. This method checks whether a particle has hit a wall and if so, it reverses the particle's velocity in the appropriate direction and adjusts the particle's position to prevent it from getting stuck in the wall. - Uses the
constrain()function from p5.js to prevent the particle's position from exceeding the canvas dimensions.
You're welcome! I'm glad you found the solution helpful. Feel free to ask if you have any other questions or need further help with your project. I'm here to assist you!
That's correct. In our current implementation, we're just drawing colored circles onto the canvas without any blending of colors. To make colors blend together, we'll need to change our approach slightly.
One possible approach is to use the blendMode() function provided by p5.js. This function changes the way colors are blended on the canvas. There are different blend modes available, but the one we're interested in for this case is ADD, which adds the color values of the new shapes and the existing canvas colors.
Here's how to modify the draw() function to include blending:
jsfunction draw() {
blendMode(BLEND);
background(0);
blendMode(ADD);
for (let p of particles) {
p.update();
p.checkWalls();
p.display();
}
}
In the code above, we first reset the blend mode to the default (BLEND) before drawing the background. Then, we set the blend mode to ADD before drawing the particles. This means the particles' colors will be added to the colors already on the canvas.
Please try this and see how the color blending behaves. You might need to adjust the color intensities of the particles to get a good result.
Note that blendMode(ADD) will not produce the same result as true light mixing, since it just adds the RGB values together. In reality, light mixing behaves more like color mixing in the subtractive (CMYK) color space. However, blendMode(ADD) can still give interesting results and may be sufficient for your needs.
Also, keep in mind that once the color value reaches its maximum (255 for each component in RGB), it won't get any brighter. This means that if you have a lot of particles passing over the same spot, the color there may quickly reach white and stay there.
I apologize for any confusion. I was explaining the limitations of using the blendMode(ADD) method for simulating light color mixing. In an ideal world, we would like to simulate how light actually mixes (based on wavelengths and human color perception), but that is quite complex.
For your needs, using blendMode(ADD) should work well enough. The color mixing won't be perfectly accurate in terms of simulating real-world light behavior, but it can create a visually appealing simulation with colors that blend together in interesting ways.
You were right to bring up the colorMode() function, as it's another important tool in p5.js for working with color. By default, p5.js uses RGB color mode, which is likely what we want for this simulation. The colorMode() function can be used to switch to HSB (Hue, Saturation, Brightness) or other color modes, but for this simulation, RGB is likely the most suitable.
So, to clarify, please use the blendMode(ADD) method as I described in the previous message, and let's see how the color blending behaves in your simulation.
Yes, you're correct. The background(0) function call in the draw function is continuously clearing the canvas before each new frame, which erases any traces of the particles' paths.
To maintain the trails behind the particles, we need to modify how we handle the background. Instead of completely clearing it every frame, we can instead overlay a semi-transparent layer. This will create a fading trail effect as the particles move.
Let's adjust the background(0) call to instead draw a semi-transparent black rectangle covering the entire canvas:
javascriptfunction draw() {
// Create a semi-transparent background to allow for trails
fill(0, 25); // semi-transparent black
noStroke();
rect(0, 0, width, height); // draw a rectangle covering the entire canvas
// The rest of your draw function...
}
In the fill function, the second argument is the alpha value (opacity), where 255 is fully opaque and 0 is fully transparent. We're using 25 here, which will make the trails fade out slowly over time.
Let's see if this gives us the effect we're looking for!
Yes, you still need the blendMode(ADD); line in the setup. This tells p5.js that when you draw a color on top of another color, you want it to add the color values together. This is what allows the colors to blend together to form new colors. The background(0); in setup provides a black background at the start, and the fill(0, 25); in draw is laying a semi-transparent layer on each frame, providing the fading trail effect.
That's great!
The background(0) function is useful for clearing the screen each frame before the new frame is drawn. This is useful if you want to avoid the trails.
By removing the background(0) function, you're allowing the trails to remain on the screen, which can create some very interesting effects.
If you add back in the background(0, 25) line (note the 25 is the alpha value which sets the transparency), then you'll get a slightly faded trail effect. This can also create some beautiful visuals.
Feel free to experiment and see what looks best for your project!
In the context of this sketch, blendMode(BLEND) is resetting the blend mode to its default state, and blendMode(ADD) is changing the blend mode to "additive" blending.
The reason for doing both is to ensure that only the parts of the code you want are affected by the blendMode(ADD) call. If you didn't reset the blend mode using blendMode(BLEND), then all the drawing operations in the draw function (including those before blendMode(ADD)) would be affected by the additive blending, which might not be the desired effect.
In other words, it ensures that the blend mode is only changed to ADD right before the particles are drawn, and then reset to BLEND afterwards (on the next frame). This ensures that the blend mode doesn't affect other parts of the drawing that it shouldn't.
In this case, though, it doesn't make much of a difference, since there aren't any other drawing operations in the draw function. So, technically, you could remove the blendMode(BLEND) call in this sketch. However, it is a good habit to reset the blend mode when you're done using a special blend mode, in case you add more drawing operations later that you don't want to be affected by the blend mode.
You're welcome! If you have any more questions or need further clarification on anything, feel free to ask. I'm here to help!
Sure. In the additive RGB color model, colors are created by adding together different amounts of red, green, and blue light. This is how colors are produced on a screen. When red, green, and blue light are all combined, we see white light.
On the other hand, the subtractive CMYK color model (cyan, magenta, yellow, and black) is used in color printing. The colors are subtracted from white light. For example, an object appears red because it absorbs (subtracts) all colors except red.
When it comes to light mixing, additive color mixing (RGB) makes sense because you're dealing with actual light sources. But the way colors blend can sometimes look more like subtractive mixing (CMYK). This is especially the case with overlapping translucent objects where each object subtracts certain wavelengths from the light that passes through.
p5.js does not directly support the CMYK color model, as it is primarily used for print, not digital screens. However, you can create your own functions to mimic subtractive mixing. It's a bit more complex, as you'd need to convert RGB values to a subtractive space and then back again. The simple addition we're using with blendMode(ADD) is a bit of a shortcut and won't give perfect results, but it's often close enough for many applications, especially considering that monitors can only display RGB. If you need more accurate color mixing, you might need to use a more complex method or a different tool or library that supports it.
You're welcome! I'm glad you found the information helpful. Indeed, the RGB (additive) color model is a good starting point especially when working with digital screens. It simplifies a lot of things and can still give you interesting results. As we progress with the simulation, we can assess if we need to make the color mixing more complex or realistic, but for a beginning, this should work fine.
If you have more questions or if there's anything else you'd like to add or change in the simulation, feel free to ask!
Sure, we can certainly add more colors and set them all to move at the same initial angle. Here's how you can do that:
javascriptfunction setup() {
createCanvas(600, 400);
colorMode(RGB, 1);
particles = [];
// Add the 6 different color particles
const colors = ['red', 'orange', 'yellow', 'green', 'blue', 'purple'];
const commonAngle = PI/4; // Set the common angle here
colors.forEach((color, i) => {
let p = new Particle(0, height / 2, color);
p.vel = p5.Vector.fromAngle(commonAngle);
particles.push(p);
});
}
function draw() {
blendMode(BLEND);
background(0, 0, 0, 0.05); // Slight trail effect
blendMode(ADD);
particles.forEach((particle) => {
particle.move();
particle.display();
});
}
This will create six particles of different colors all moving in the same direction specified by commonAngle. The colors array stores the names of the colors for the particles. The forEach loop then creates a new particle for each color in the array, with the color determined by the current element of the array.
Please replace the Particle class's constructor and the display() function with the following:
javascriptclass Particle {
constructor(x, y, color) {
this.pos = createVector(x, y);
this.vel = createVector(0, 0);
this.acc = createVector(0, 0);
this.diameter = 5;
this.color = color;
}
// Other methods...
display() {
noStroke();
fill(this.color);
circle(this.pos.x, this.pos.y, this.diameter);
}
}
In the constructor, we've added a new parameter color that sets the color of the particle, and we've replaced the fill() call in display() with fill(this.color) to use the color specified for each particle.
Remember, you might need to adjust the initial position and the commonAngle to get the desired effect in your canvas.
Sure, here's the full code:
javascriptlet particles;
function setup() {
createCanvas(600, 400);
colorMode(RGB, 1);
particles = [];
// Add the 6 different color particles
const colors = ['red', 'orange', 'yellow', 'green', 'blue', 'purple'];
const commonAngle = PI/4; // Set the common angle here
colors.forEach((color, i) => {
let p = new Particle(0, height / 2, color);
p.vel = p5.Vector.fromAngle(commonAngle);
particles.push(p);
});
}
function draw() {
blendMode(BLEND);
background(0, 0, 0, 0.05); // Slight trail effect
blendMode(ADD);
particles.forEach((particle) => {
particle.move();
particle.display();
particle.checkBoundaries();
});
}
class Particle {
constructor(x, y, color) {
this.pos = createVector(x, y);
this.vel = createVector(0, 0);
this.acc = createVector(0, 0);
this.diameter = 5;
this.color = color;
}
move() {
this.vel.add(this.acc);
this.pos.add(this.vel);
this.acc.mult(0);
}
display() {
noStroke();
fill(this.color);
circle(this.pos.x, this.pos.y, this.diameter);
}
checkBoundaries() {
if (this.pos.x > width - this.diameter/2) {
this.pos.x = width - this.diameter/2;
this.vel.x *= -1;
} else if (this.pos.x < this.diameter/2) {
this.pos.x = this.diameter/2;
this.vel.x *= -1;
}
if (this.pos.y > height - this.diameter/2) {
this.pos.y = height - this.diameter/2;
this.vel.y *= -1;
} else if (this.pos.y < this.diameter/2) {
this.pos.y = this.diameter/2;
this.vel.y *= -1;
}
}
}
The notation this.pos and this.vel are just different variable names for the position and velocity of the particles. I changed them to make the code a bit more readable and clear. If you want to keep the old names, you can replace this.pos with this.position and this.vel with this.velocity in the Particle class, and make corresponding changes in the setup() and draw() functions. The functionality will remain the same.
The this.acc variable, which stands for acceleration, is not currently being used in this particle system, but it's included here because it's a common feature of many physics simulations.
In more complex particle systems, acceleration can be used to simulate effects such as gravity, wind, or other forces. For example, if you wanted to simulate a force that pushes all particles down the screen (like gravity), you could add a constant downward acceleration to each particle.
However, in this current code, this.acc isn't being used and you could remove it without any effect on the program. It's included more out of habit and the anticipation of potentially adding more complex dynamics in the future.
My apologies for the confusion, that might be an oversight on my part. If we're still following the additive RGB color mixing model, the colorMode should remain as colorMode(ADD);. This is because we want our colors to mix in the way light would, with red, green, and blue combining to create white.
So yes, you should maintain the colorMode(ADD); in your code for the colors to mix correctly. I apologize for the confusion and I appreciate your patience.
I apologize for the confusion, you're right. colorMode(ADD) is not valid, and colorMode(RGB, 255, 255, 255, 100); was indeed the line we used to set the color mode in our sketch. What I meant to communicate was that our colors are added together like lights would, due to our usage of the additive RGB color space and the blendMode(ADD) function. I regret the error.
The correct line to continue using is indeed colorMode(RGB, 255, 255, 255, 100);. The parameters we provided mean that we're using the RGB color space, with each color channel ranging from 0 to 255, and an alpha (transparency) channel ranging from 0 to 100. I apologize for any confusion my previous message may have caused.
Please continue using colorMode(RGB, 255, 255, 255, 100); in your code.
I apologize for the confusion. The white display you are seeing is due to the overlap of all colors with blendMode(ADD). When all RGB colors are at their maximum values (255,255,255), the resulting color is white. This occurs because each of the six particles starts from the same position and moves in the same direction, hence they overlap entirely creating a white path.
There are a few potential solutions to this:
Start the particles from different positions or move them in slightly different directions. This will allow the individual colors to be visible as they will not be overlapping entirely.
Alter the colors to use lower RGB values. This will
Ah, I see. My apologies for misunderstanding. If the entire screen is white, it could be due to the color of the background or an error in the code.
Given that we have removed the background(0); line in our draw() function to allow for the persistence of the particles trails, the color of the canvas should remain black.
Let's try going back to our previous colorMode and also add background(0); to setup() to ensure we are starting with a black background.
javascriptlet particles = [];
let colors = ["red", "orange", "yellow", "green", "blue", "purple"];
function setup() {
createCanvas(windowWidth, windowHeight);
colorMode(RGB, 255, 255, 255, 100);
angleMode(DEGREES);
background(0);
for (let i = 0; i < colors.length; i++) {
let particle = new Particle(
createVector(width / 4, height / 2),
p5.Vector.fromAngle(45),
colors[i]
);
particles.push(particle);
}
}
function draw() {
blendMode(ADD);
particles.forEach((particle) => {
particle.move();
particle.display();
});
}
class Particle {
constructor(pos, vel, color) {
this.pos = pos;
this.vel = vel;
this.color = color;
this.acc = createVector(0, 0);
}
move() {
this.vel.add(this.acc);
this.pos.add(this.vel);
this.acc.mult(0);
if (this.pos.x < 0 || this.pos.x > width) {
this.vel.x *= -1;
}
if (this.pos.y < 0 || this.pos.y > height) {
this.vel.y *= -1;
}
}
display() {
stroke(this.color);
strokeWeight(20);
point(this.pos.x, this.pos.y);
}
}
Try running this version and let me know if the entire screen is still white. If it is, it's possible there's a mistake somewhere in the code that I'm not seeing, or some other aspect of the environment causing an issue.
I apologize for any confusion. In trying to help you with your project, it's sometimes necessary to make adjustments to the existing code. However, I certainly understand the importance of maintaining the integrity of your original work.
The addition of background(0); in the setup() function is meant to ensure the initial canvas is black before any particles are drawn. This typically doesn't need to be in the draw() function unless you want to clear the screen every frame, which we are not doing in this case as we want to see the paths of the particles.
In future responses, I'll do my best to make only necessary changes and maintain as much of the original code as possible. Thanks for your patience and understanding!
Thank you for sharing the latest version of your code. The current code should create 6 particles of different colors (red, orange, yellow, green, blue, and purple), all moving in the same initial direction.
With the colorMode(RGB, 255, 255, 255, 100); in your setup, each particle's color is semi-transparent, allowing for some blending of colors as they overlap. And with the blending mode set to ADD, colors will add together where particles overlap, creating additive color mixing effects. It also keeps a trail of the particles' paths, but since the particles are semi-transparent, older paths gradually fade as more and more particles pass over them.
The checkBoundaries() method in the Particle class ensures that the particles bounce back when they hit the edges of the canvas, keeping them within the visible area.
Is there anything specific you would like to adjust or add to this code? Please let me know how you would like to continue!
To separate the particles by height in the y direction, you can calculate the y-position based on the index of the particle. One way to do this would be to divide the height of the canvas by the number of particles plus 1, and multiply by the index of each particle (plus 1).
Here is how you would modify your code:
javascriptfunction setup() {
createCanvas(600, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles = [];
// Add the 6 different color particles
const colors = ["red", "orange", "yellow", "green", "blue", "purple"];
const commonAngle = PI / 4; // Set the common angle here
colors.forEach((color, i) => {
let y = ((height / (colors.length + 1)) * (i + 1)); // Calculate y-position based on index
let p = new Particle(0, y, color);
p.vel = p5.Vector.fromAngle(commonAngle);
particles.push(p);
});
}
In this code, the y variable calculates the y-position for each particle based on its index in the colors array. By dividing the height of the canvas by the number of particles plus 1 (height / (colors.length + 1)), we create equal-sized sections of the canvas for each particle. Multiplying this value by the index of the particle plus 1 (* (i + 1)) gives a different y-position for each particle, evenly spaced along the height of the canvas.
p5.js has limited ability to interpret color names like "orange" correctly. It is able to understand basic color names like "red", "green", "blue", "yellow", etc. However, it struggles with more nuanced color names like "orange". Instead of using the name, it's often better to use RGB or HSB values to achieve the color you desire.
To get the color orange, you can use the RGB values (255, 165, 0).
Here's how you can update the color assignment in your code:
javascriptconst colors = [
[255, 0, 0], // red
[255, 165, 0], // orange
[255, 255, 0], // yellow
[0, 128, 0], // green
[0, 0, 255], // blue
[128, 0, 128] // purple
];
colors.forEach((color, i) => {
let y = ((height / (colors.length + 1)) * (i + 1));
let p = new Particle(0, y, color);
p.vel = p5.Vector.fromAngle(commonAngle);
particles.push(p);
});
And remember to adjust the fill command in the Particle's display method to accept an array:
javascriptfill(this.color[0], this.color[1], this.color[2]);
These changes should allow you to display a more distinct orange color.
Sorry for any confusion. The colors array I provided assumes that the colorMode is RGB, which was the case in your original code
I apologize for the confusion. In p5.js, "orange" is not a named color as it is in some other contexts. In p5.js, you need to define colors using RGB or HSB values.
Here's a way to create an orange color using RGB:
javascriptlet orange = color(255, 165, 0);
Then you can replace "orange" with the variable orange in your colors array.
So your modified colors array should be:
javascriptconst orange = color(255, 165, 0);
const colors = [color(255, 0, 0), orange, color(255, 255, 0), color(0, 255, 0), color(0, 0, 255), color(128, 0, 128)];
I apologize for the confusion. If you've already tried that approach and the orange color still appears yellow, it might be due to the additive color blending. In additive color blending, colors can change based on the colors they are combined with. Since we are using blendMode(ADD), the colors can mix and result in different colors.
If you strictly want the particles to maintain their initial colors without blending, you may want to remove blendMode(ADD). But bear in mind, you will lose the color mixing effect we have been trying to achieve.
Also, you may want to experiment with different RGB values to get a color that appears more orange on your screen. Monitors can sometimes display colors slightly differently, and the blending of colors can also affect the perceived color.
I see, thank you for clarifying. Yes, you're correct. In p5.js, "orange" is indeed a valid color name that can be passed into the fill() function.
The additive blending mode (blendMode(ADD)) will cause the RGB values of overlapping colors to add together, which can sometimes result in colors appearing different than their original values. For example, if a red particle (255, 0, 0) overlaps with a green particle (0, 255, 0), the resulting color will be yellow (255, 255, 0).
I apologize for the confusion. If you want to keep the additive blending but also want the orange color to appear more distinct, you might need to adjust the initial colors or the blending settings. It's also worth noting that the perceived color can be influenced by many factors, including the colors of nearby particles and the background color.
I see, the additive blend mode is still influencing the colors even when the particles are not overlapping with other particles. This is because additive blend mode also affects the way colors blend with the background.
In additive blend mode, the colors are mixed by adding their red, green, and blue values together. When you have a black background (0, 0, 0), adding any color to it will result in that color itself. However, due to the way colors are displayed on digital screens and the characteristics of human color perception, this can sometimes result in colors looking different than expected, especially for colors that are made by mixing red, green, and blue light, like orange.
When you draw a semi-transparent orange particle on a black background in additive blend mode, the red and green light from the particle will add to the black background. Since the particle is semi-transparent, some of the black background will still be visible, which can make the orange color appear less intense and more yellowish.
One potential workaround is to make the particles fully opaque by setting the alpha value to 255. This will make the orange particles appear more orange, but it will also remove the transparency and blending effects. Here's how you can do this:
javascriptfill(this.color[0], this.color[1], this.color[2], 255); // Fully opaque particles
Another potential workaround is to use a different blend mode that blends colors in a way that preserves the appearance of orange more effectively. For example, you could try using the BLEND mode, which blends colors in a way that is more similar to mixing paints. However, this will also change the appearance of the other colors and the way they blend together.
The additive blending mode will interact with a white background (255, 255, 255) differently than with a black background. Instead of adding color to black, you're adding color to white.
When using additive blending with a white background, colors may appear washed out or lighter than expected. This is because adding any color to white, in RGB color space, still results in white. When you draw semi-transparent colors on a white background, the underlying white will mix with your color, which can lighten the colors, sometimes dramatically.
In the case of orange, if it's displayed semi-transparently on a white background in additive blending mode, the underlying white will show through, resulting in a lighter, more yellowish color. This is because orange is made up of red and green, and adding more brightness to green (which is part of the white background) can make the color appear more yellow.
In short, the logic is similar whether you have a black or white background: the blending mode determines how your colors mix with the background and with each other. The results you see are due to the characteristics of the RGB color space and how colors are displayed on digital screens.
I apologize for the confusion. My previous explanations assumed that the color model and the blending mode were consistent with the default settings in p5.js. However, it seems the issue you're encountering is more complex than expected.
Additive color blending can
Yes, that's a great description of how additive color blending works. Each frame, when you draw a new circle, the color of the pixels covered by that circle gets added to the color that was already there. If the new color would push one or more of the RGB channels over 255, those channels are indeed capped at 255.
So, for example, with orange ([255, 165, 0]), after the first few frames, the red channel is already at 255. With each additional frame, the green channel keeps increasing until it, too, reaches 255, resulting in yellow ([255, 255, 0]).
And for purple ([128, 0, 128]), both the red and blue channels keep increasing, but since they start at the same value and increase at the same rate, the color remains a shade of purple (just a brighter one as it approaches [255, 0, 255]).
It seems you've understood the behavior of blendMode(ADD) quite well. Remember that this is just one way of blending colors and may not be the right choice for all visual effects. Different modes can create different artistic effects, and the best choice depends on your specific goals for your project.
Sure, I'd be happy to delve into that!
First off, it's important to note that the RGB color model used in displays is based on the trichromatic nature of human vision. We have three types of color-sensitive cones in our eyes that respond to short (S, roughly blue), medium (M, roughly green), and long (L, roughly red) wavelengths of light. The brain processes the signals from these cones to perceive color.
In the real world, light mixing behaves according to the principles of additive color. When light of different colors combines, the resulting color is the sum of the input colors. For example:
- Red light + Green light = Yellow light
- Red light + Blue light = Magenta light
- Green light + Blue light = Cyan light
- Red light + Green light + Blue light = White light
This might seem counterintuitive if you're used to mixing paints or other pigments, which follow the principles of subtractive color. For example, if you mix yellow and cyan paint, you get green, but if you mix yellow and cyan light, you get white.
The RGB model is used in systems that emit light, such as televisions and computer monitors. Each pixel in an RGB display consists of three small light-emitting elements, one red, one green, and one blue. By varying the intensity of these three elements, the display can produce a wide range of colors.
However, computer graphics is a bit different from physical light mixing. When colors are added in computer graphics, their values are just added together, and if the sum exceeds the maximum (usually 255), it's capped at the maximum. This can sometimes result in colors that seem unusual if you're thinking in terms of physical light. The orange turning to yellow in your p5.js sketch is a good example of this. In the real world, mixing two orange lights would just give you a brighter orange light, not yellow. But in the RGB color model used in p5.js, the green channel keeps increasing until it reaches the maximum, turning the color to yellow.
I hope this gives you a better understanding of how light mixing works both in the physical world and in computer graphics. If you have any more questions, feel free to ask!
Yes, that's definitely possible and it could help reduce the issue of colors shifting due to additive blending.
The line() function in p5.js can be used to draw a line from one point to another. You'll need to remember the particle's previous position at each step so that you can draw a line from the previous position to the current one.
Here's how you could modify the Particle class and draw() function to achieve this:
javascriptclass Particle {
constructor(x, y, color) {
this.pos = createVector(x, y);
this.prevPos = this.pos.copy();
this.vel = createVector(0, 0);
this.diameter = 5;
this.color = color;
}
move() {
this.prevPos = this.pos.copy(); // Store the current position before updating it
this.vel.add(this.acc);
this.pos.add(this.vel);
}
display() {
strokeWeight(this.diameter);
stroke(this.color);
line(this.prevPos.x, this.prevPos.y, this.pos.x, this.pos.y);
}
// ... other methods ...
}
In the display() method, I'm using stroke() to set the color of the line and strokeWeight() to set its thickness. noStroke() and fill() are no longer needed, because we're not drawing circles anymore. The line is drawn from the particle's previous position to its current position.
Remember to also remove the noStroke() function call in the draw() function. The rest of the sketch should remain unchanged.
Give it a try and see if it solves the issue with the orange color turning yellow.
Yes, as long as you are drawing overlapping shapes with additive blending and colors that are not at the maximum values for all RGB components, you will have some shift in colors. This is an inherent feature of the additive blending mode.
If the effect is not desired in your case, there are a couple of other potential solutions to consider:
Use the
NORMALblend mode, which doesn't add colors together. However, with this mode, the colors won't blend together like they do in theADDmode.Design your color palette and particle movement carefully to minimize the overlap of particles with different colors.
Use a different method to achieve the color mixing effect. For example, you could use a shader, which is a special kind of program that runs on the GPU and can be used for more advanced graphics effects. However, shaders are significantly more complex to write and use than regular p5.js code.
Experiment with different colors and see if you can find a set of colors that look good with additive blending, even if they don't match the original colors exactly.
If you're interested in realistic light mixing, you may want to look into physical-based rendering (PBR) methods, although these are typically much more complex and resource-intensive than simple color blending.
Perfect! This version of your code uses line() instead of circle() for drawing the particles, and stroke() instead of fill() for setting the color. It keeps track of the previous position of each particle and draws a line from the previous position to the current position at each step, creating a trail effect.
Moreover, it also includes changes in the Particle class to store the previous position (this.prevPos), and in the move() method to update this.prevPos before changing this.pos. The display method also has been updated to draw a line from this.prevPos to this.pos.
In the current state, the code is not making use of any blending effects (as all the blending related code is commented out) and it is drawing each particle in the respective color with full opacity.
Is there anything specific you would like to adjust or add to this code now?
Yes, you're absolutely correct. In order to achieve the effect of light rays starting all on top of each other and appearing white, and then splitting into separate colors, you would indeed need to use some form of color blending.
The blend mode ADD is probably the closest to what you want in this context, as it adds the RGB values of the colors, mimicking the way light colors combine. With this blend mode, if you have the red, green, and blue rays overlapping, they will appear white (since adding red, green, and blue light results in white).
However, as you've already discovered, ADD blending can also have some unintended side effects when used with semi-transparent colors. It can also cause colors to become more intense or shift to a different hue when they overlap. For example, we saw that orange turns to yellow when several semi-transparent orange circles overlap.
To achieve the effect you want, you might have to make some compromises or try different approaches. For example, you could start with all rays in the same position but with colors set to very low opacity, then increase the opacity as they move further from the source, so the individual colors become more apparent as they separate. You could also try using different blend modes or combinations of blend modes to see if they produce a more desirable result.
In any case, accurately simulating the behavior of light and color in a physics-based manner can be quite complex, especially when you also want it to look visually pleasing. It may involve some trial and error to find the best approach for your specific needs.
Sure, to draw a triangle you can use the triangle() function in p5.js, which takes six arguments, these being the x and y coordinates of the three points of the triangle. For example, triangle(x1, y1, x2, y2, x3, y3).
Here's how you can add a simple triangle to the center of your canvas:
javascriptfunction setup() {
createCanvas(600, 400);
background(0);
//...
}
function draw() {
//...
fill(255, 255, 255, 100); // Set the color of the triangle (semi-transparent white)
noStroke(); // Don't draw an outline
triangle(width / 2, height / 2, width / 2 - 50, height / 2 - 100, width / 2 + 50, height / 2 - 100); // Draw the triangle
//...
}
This will draw a triangle in the center of the canvas. You can adjust the coordinates and color as needed to suit your project.
When it comes to simulating the refractive index and the behavior of light rays when they hit the triangle (which I'm guessing is meant to represent a prism), that's quite a bit more complex. Realistically simulating refraction involves some understanding of physics and potentially some more advanced programming techniques.
Do you want to represent the refraction visually, or just change the direction of the particles when they hit the triangle? The first one could be quite challenging, the latter is simpler. Let me know what level of detail you are aiming for in your simulation.
Yes, you're correct. Snell's law is what we'd use here, which states that the ratio of the sine of the angles of incidence and transmission is equal to the ratio of the phase velocity (speed of light) in the two media, or equivalently, to the indices of refraction. The formula is as follows:
n1 * sin(theta1) = n2 * sin(theta2)
Where:
- n1 is the index of refraction of the first medium
- n2 is the index of refraction of the second medium
- theta1 is the angle between the incident ray and the line perpendicular to the surface (normal line)
- theta2 is the angle between the refracted ray and the normal line
The refractive index of a medium varies slightly with the frequency (and therefore color) of light, which is what causes dispersion - different colors refracting by different amounts, which is what we see in a rainbow or the splitting of white light by a prism.
For simplicity, we could approximate and say the incident light is hitting the prism perpendicular to its surface (theta1 = 0), which simplifies Snell's law to:
sin(theta2) = n1 / n2
So, each color of light could have a slightly different index of refraction when entering the prism, leading to a different refraction angle for each one.
For implementation, you'd need a way to detect when a particle hits the prism, and then update its velocity vector based on the refracted angle. This angle can be calculated based on Snell's law and the color-dependent index of refraction.
The specifics of how you do this would depend on the details of your project, like how you're handling collisions and movement, but this is the general idea. If you're interested in a more accurate simulation, you might want to look into ray tracing, which is a technique used in computer graphics to simulate the propagation of light.
Does that help, and do you want to proceed in this direction?
I apologize for the error in my previous response. You're correct, for normal incidence, where the light is incident perpendicular to the boundary (i.e., theta1 = 0 degrees), the light will not change direction, as sin(0) = 0. This implies that theta2 is also 0, meaning the light continues along the same path.
However, in the context of a prism, light doesn't enter and exit at normal incidence. A prism is typically a triangular shape, and light enters at one face and exits through another, both of which are inclined to the direction of light. In this case, light will refract and change its direction, both on entry and exit.
The refraction on entering the prism would cause the light to bend towards the normal (i.e., towards the base of the triangle in a typical prism) and then bend again, away from the normal, when exiting the prism. It's this double refraction, combined with the dispersion (color-dependence) of the refractive index, that causes the separation of colors in a prism.
Again, I apologize for the confusion in my previous response. Thank you for pointing out the error.
I apologize for the confusion earlier. Yes, you're right. For a prism, light typically enters at an angle (not normal incidence), and the change in angle as light refracts is dependent on the wavelength of light, leading to dispersion and the separation of colors. The angle change can be calculated using Snell's Law as we discussed earlier, with different angles for each color due to their different refractive indices. Let's carry on with implementing this for the prism in our simulation. We'll create a triangular region in the center of the screen to represent the prism. When a particle enters this region, we'll change its direction based on Snell's law. The amount of change will be determined by the color of the particle. Would you like to continue with this approach?
Alright. To do this, we first need to create a triangular region for our prism. Once we've created this region, we can then check if a particle is inside this region and, if it is, change its direction based on Snell's law. For simplicity, let's assume that the refractive index of our prism is 1.5 (which is around the refractive index of glass for visible light) and that the refractive index of the surrounding medium (presumably air) is 1. The refractive index for each color is only slightly different, so for simplicity, we could approximate them all to be the same.
javascriptclass Particle {
constructor(x, y, color, refrIndex) {
this.pos = createVector(x, y);
this.prevPos = this.pos.copy();
this.vel = createVector(0, 0);
this.diameter = 5;
this.color = color;
this.refrIndex = refrIndex;
}
// ...
refract() {
let prism = {
a: createVector(width / 2 - 50, height / 2 - 50),
b: createVector(width / 2 + 50, height / 2 - 50),
c: createVector(width / 2, height / 2 + 50),
};
// Check if the particle is inside the prism
if (this.pos.x > prism.a.x && this.pos.x < prism.b.x && this.pos.y > prism.a.y && this.pos.y < prism.c.y) {
// Calculate the new velocity based on Snell's law
let normal = createVector(1, 0); // Normal at the surface where the light enters the prism
let incidence = p5.Vector.sub(this.vel, normal);
incidence.normalize();
let theta1 = incidence.angleBetween(normal);
let theta2 = asin(sin(theta1) * this.refrIndex);
let refracted = p5.Vector.fromAngle(theta2);
this.vel = refracted.mult(this.vel.mag());
}
}
move() {
this.prevPos = this.pos.copy();
this.vel.add(this.acc);
this.pos.add(this.vel);
this.refract();
}
}
Now, in the move method, we call the new refract method to change the direction of the particle if it is inside the prism. This example assumes that the refractive index for each color is the same. If you want to use different refractive indices for each color, you can adjust the refrIndex property for each particle accordingly. Remember to draw the prism in the draw function so you can see it on the screen. Note that I didn't add the necessary checks to change the direction again when the light exits the prism. You could add this yourself if you like.
This example is a simplified version and does not take into account many real world factors, such as the change of the normal vector at different positions on the prism surface or the slight variations in refractive index for different colors of light. This should give you a basic idea of how to implement refraction in your particle system, though.
Also, be aware that the angleBetween and fromAngle functions in p5.js use radians, not degrees, so make sure to convert your angles to radians if they are initially in degrees. In JavaScript, you can convert from degrees to radians with radians = degrees * (PI/180), and you can convert from radians to degrees with degrees = radians * (180/PI).
I see where you're coming from. If we assume all wavelengths of light to have the same refractive index, then they will all refract the same amount and will not spread out into a spectrum of colors. This would indeed contradict your original goal of simulating how light splits into different colors as it goes through a prism.
In the context of your simulation, you would indeed want different refractive indices for different colors in order to model the dispersion of light (the splitting of white light into its component colors). This phenomenon is a result of the refractive index of a material being dependent on the wavelength of light, which means different colors (wavelengths) of light refract at slightly different angles when passing through a prism.
For instance, in the visible spectrum, red light is refracted the least and violet light is refracted the most, with the other colors falling in between. To model this in your simulation, you could assign each color a slightly different refractive index.
However, it's important to note that these differences in refractive index are relatively small. For example, in glass, the refractive index varies from about 1.51 for red light to about 1.53 for violet light. Even though these differences are small, they result in noticeable dispersion because of the large number of light waves involved.
Given that, you could consider assigning each color of particle a slightly different refractive index, proportional to its position in the color spectrum. You would then adjust the refract method to use the particle's specific refractive index when calculating the refraction angle.
However, keep in mind that this is a simplification of the complex nature of light refraction and dispersion, and the results will not perfectly match physical reality.
Great! Let's proceed with that approach then. We will assign each color a slightly different refractive index, based on its position in the spectrum. Here is how we could modify the code to include this:
javascriptlet particles;
function setup() {
createCanvas(600, 400);
colorMode(RGB, 255, 255, 255, 100);
background(0);
particles = [];
// Add the 6 different color particles
const colors = [
[255, 0, 0], // red
[255, 165, 0], // orange
[255, 255, 0], // yellow
[0, 255, 0], // green
[0, 0, 255], // blue
[128, 0, 128], // purple
];
const refrIndices = [
1.51, // red
1.52, // orange
1.52, // yellow
1.53, // green
1.53, // blue
1.54, // purple
];
const commonAngle = PI / 4; // Set the common angle here
colors.forEach((color, i) => {
let y = (height / (colors.length + 1)) * (i + 1); // Calculate y-position based on index
let p = new Particle(0, y, color, refrIndices[i]);
p.vel = p5.Vector.fromAngle(commonAngle).mult(10);
particles.push(p);
});
}
class Particle {
constructor(x, y, color, refrIndex) {
this.pos = createVector(x, y);
this.prevPos = this.pos.copy();
this.vel = createVector(0, 0);
this.diameter = 5;
this.color = color;
this.refrIndex = refrIndex; // Add refractive index to the particle class
}
// When the particle hits the boundary of the prism, calculate the refraction
checkBoundaries() {
if (this.pos.x > width - this.diameter / 2) {
this.pos.x = width - this.diameter / 2;
this.vel = this.refract(this.vel, this.refrIndex);
} else if (this.pos.x < this.diameter / 2) {
this.pos.x = this.diameter / 2;
this.vel = this.refract(this.vel, 1 / this.refrIndex);
}
if (this.pos.y > height - this.diameter / 2) {
this.pos.y = height - this.diameter / 2;
this.vel.y *= -1;
} else if (this.pos.y < this.diameter / 2) {
this.pos.y = this.diameter / 2;
this.vel.y *= -1;
}
}
// Refraction calculation, using Snell's law
refract(v, n) {
let u = v.copy();
u.normalize();
let dt = u.dot(this.n);
let discr = 1.0 - n * n * (1.0 - dt * dt);
if (discr > 0) {
return p5.Vector.sub(p5.Vector.mult(u, n), p5.Vector.mult(this.n, (n * dt + sqrt(discr))));
} else {
return createVector(0, 0); // No refraction possible
}
}
}
This is the basic idea, but we need to define the boundaries of the prism and the normal vector (this.n in the refract method) at each boundary. The normal vector should be perpendicular to the boundary and point towards the outside of the prism.
We also need to decide what to do when a particle hits a boundary at a very steep angle, where refraction isn't possible (when discr <= 0 in the refract method). In the example above, I just stop the particle in that case (return createVector(0, 0);), but that might not be the best solution. We could also reflect the particle like it was a mirror, or let it pass through the boundary without refracting, or something else.
Note: The values of the refractive indices I used are just made up, not actual values for these colors. You might want to look up more accurate values or adjust them to get the effect you want.
You're correct, I made a mistake in my explanation and sample code. I apologize for any confusion caused. The boundaries of the canvas and the boundaries of the prism should indeed be handled separately.
If a particle reaches the boundary of the canvas, we can simply reflect it back.
If a particle reaches the boundary of the prism, we need to determine whether it's entering or exiting the prism, and then change its direction based on Snell's law and the refractive indices of the materials (air and glass). This also involves calculating the normal at the point of incidence, which depends on the shape of the prism.
Let's separate these two concepts properly. For now, let's assume the prism is a triangle in the middle of the canvas. For simplicity, let's say it's an equilateral triangle, although you could certainly use any shape you like for the prism.
We need to add two new methods to the Particle class:
reflect()- when the particle hits the canvas boundary.refract()- when the particle crosses a prism boundary.
In the checkBoundaries() method, we first check if the particle is hitting the canvas boundary and reflect it if it is. Then we check if the particle is crossing a prism boundary and refract it if it is.
We also need to add a new class for the prism. This class could have a method that checks if a particle is crossing its boundary, and if so, calculates the normal at that point and whether the particle is entering or exiting the prism.
The exact implementation of these methods would depend on the specific layout of the canvas and the prism. It's probably going to involve a bit of trigonometry and geometry.
Are you comfortable proceeding with this approach? If not, could you please specify which aspects you need more help with?
Great! Let's start with creating a Prism class that we will define as an equilateral triangle. We will define the Prism in terms of its center, its size (the length of one side), and the orientation of its apex (up or down). For simplicity, we will start with an upwards-pointing triangle in the center of the canvas with a size that fits well within the canvas.
We will also add methods to check if a particle is crossing a boundary, to calculate the normal at a boundary point, and to determine whether the particle is entering or exiting.
Here is a skeleton of the Prism class:
jsclass Prism {
constructor(x, y, size, apexUp) {
this.pos = createVector(x, y);
this.size = size;
this.apexUp = apexUp;
}
display() {
// TODO: Draw the triangle
}
isCrossingBoundary(particle) {
// TODO: Check if the particle is crossing a boundary
// Return the side number (0, 1, 2) if it is, or -1 if it's not
return -1;
}
calculateNormal(side) {
// TODO: Calculate the normal vector at the given side
// Return it as a p5.Vector
return createVector(0, 0);
}
isEntering(particle, side) {
// TODO: Determine whether the particle is entering or exiting
// Return true if it's entering, false if it's exiting
return false;
}
}
Next, we will update the Particle class to use this Prism class. We will add a prism parameter to the Particle constructor and store it as an instance variable. Then, we will modify the checkBoundaries() method to also check if the particle is crossing a prism boundary and, if so, refract it.
Here is the skeleton of the updated Particle class:
jsclass Particle {
constructor(x, y, color, prism) {
this.pos = createVector(x, y);
this.prevPos = this.pos.copy();
this.vel = createVector(0, 0);
this.diameter = 5;
this.color = color;
this.prism = prism;
}
// ...
checkBoundaries() {
// Check if the particle is hitting the canvas boundary
// If it is, reflect it
// ...
// Check if the particle is crossing a prism boundary
let side = this.prism.isCrossingBoundary(this);
if (side >= 0) {
// If it is, refract it
let normal = this.prism.calculateNormal(side);
let entering = this.prism.isEntering(this, side);
this.refract(normal, entering);
}
}
refract(normal, entering) {
// TODO: Refract the particle
}
}
Finally, we will create a Prism instance in the setup() function and pass it to each Particle.
jsfunction setup() {
// ...
let prism = new Prism(width / 2, height / 2, min(width, height) / 3, true);
// Add the 6 different color particles
// ...
let p = new Particle(0, y, color, prism);
// ...
}
Does this make sense so far? Please let me know if you have any questions or need help with the details of any of the methods.
You're absolutely correct. The prism can be a shared object in the global scope, and we don't need to attach it to each particle. That was an oversight on my part.
You can define the prism in the setup function or even at the beginning of your sketch, outside any function, to make it available globally.
Here is how to do it:
javascriptlet particles;
let prism;
function setup() {
// ...
prism = new Prism(width / 2, height / 2, min(width, height) / 3, true);
// Add the 6 different color particles
// ...
let p = new Particle(0, y, color);
// ...
}
Then, in the Particle class, you just call prism.isCrossingBoundary(this) etc., without needing to attach the prism object to each particle. This way, the prism is a single shared object that all particles can refer to.
Thank you for pointing that out. I appreciate your careful consideration of the code design.
Absolutely! Teamwork indeed!
Let's continue then. Now we need to provide the implementation for the Prism class and its method isCrossingBoundary. We'll also define the Particle class's checkPrismBoundary method.
javascriptclass Prism {
constructor(x, y, size, isSquare) {
this.pos = createVector(x, y);
this.size = size;
this.isSquare = isSquare; // Whether the prism is square or triangular
}
// Check whether a given particle is crossing the boundary of the prism
isCrossingBoundary(particle) {
// If the prism is square, we simply check whether the particle is within the square bounds
if (this.isSquare) {
let halfSize = this.size / 2;
return (particle.pos.x > this.pos.x - halfSize && particle.pos.x < this.pos.x + halfSize
&& particle.pos.y > this.pos.y - halfSize && particle.pos.y < this.pos.y + halfSize);
}
// If the prism is triangular, the calculation is a bit more complex and is left as an exercise
// For simplicity, you can start with a square prism
return false;
}
// Draw the prism for visualization
draw() {
fill(255, 50); // Semi-transparent white
if (this.isSquare) {
square(this.pos.x - this.size / 2, this.pos.y - this.size / 2, this.size);
}
// If the prism is triangular, the drawing code is a bit more complex and is left as an exercise
}
}
// ...
class Particle {
// ...
// Check whether this particle is crossing the boundary of the prism and react accordingly
checkPrismBoundary() {
if (prism.isCrossingBoundary(this)) {
// If the particle is entering the prism, adjust its velocity (direction of movement) according to Snell's law
// ...
// If the particle is exiting the prism, adjust its velocity back according to Snell's law
// ...
}
}
// ...
}
In the draw function, we also need to draw the prism so that we can see where it is:
javascriptfunction draw() {
// ...
prism.draw();
// ...
}
This is the basic structure for the prism and its interaction with the particles. The actual calculation according to Snell's law is a bit more complex and I have left it out here for simplicity. I can help you implement it if you'd like to proceed in this direction.
Also note that for the triangular prism, the shape of the boundary and thus the calculation of whether a particle is crossing it is a bit more complex. Again, I can help with that if you're interested.
I apologize for any confusion. Let's take one step at a time. Now that we've checked whether the particle is inside the prism, we need to adjust its velocity based on the Snell's law if it's entering or exiting the prism. This is where things get a bit complex.
Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities (v1 / v2) in the two media, or equivalently, to the reciprocal of the ratio of the indices of refraction (n2 / n1):
n1 * sin(theta1) = n2 * sin(theta2)
We'll be treating our canvas as having an index of refraction of 1 (like air), and the prism as having an index of refraction of 1.5 (approximate value for glass).
Since the sine function is hard to work with, we'll work with the tangent function, as the tangent of an angle in a right triangle is the ratio of the length of the opposite side to the length of the adjacent side. Therefore, the change in velocity can be expressed as a change in the y-component of the velocity vector (which corresponds to the "opposite side" in a right triangle) divided by the x-component of the velocity vector (which corresponds to the "adjacent side" in a right triangle).
Here's the adjusted checkPrismBoundary method:
javascriptclass Particle {
// ...
// Check whether this particle is crossing the boundary of the prism and react accordingly
checkPrismBoundary(prism) {
if (prism.isCrossingBoundary(this)) {
let n1, n2; // Indices of refraction
let velYAdj; // Adjusted y-component of the velocity
if (this.insidePrism) { // Exiting the prism
n1 = 1.5;
n2 = 1;
this.insidePrism = false;
} else { // Entering the prism
n1 = 1;
n2 = 1.5;
this.insidePrism = true;
}
// Calculate the adjusted y-component of the velocity
let angle = atan(this.vel.y / this.vel.x); // Original angle of the velocity vector
let angleAdj = asin(n1 / n2 * sin(angle)); // Adjusted angle according to Snell's law
velYAdj = tan(angleAdj) * this.vel.x; // Adjusted y-component of the velocity
// Adjust the y-component of the velocity
this.vel.y = velYAdj;
}
}
// ...
}
Here, this.insidePrism is a new instance variable for Particle that needs to be initialized in the Particle constructor:
javascriptclass Particle {
constructor(x, y, color) {
// ...
this.insidePrism = false; // Whether this particle is currently inside the prism
}
// ...
}
Note that checkPrismBoundary now takes prism as a parameter, so it needs to be called like this in the draw function:
javascriptfunction draw() {
// ...
particles.forEach((particle) => {
particle.move();
particle.checkPrismBoundary(prism);
particle.display();
particle.checkBoundaries();
});
// ...
}
This is a simplified implementation that makes a number of assumptions (e.g., that the velocity vector doesn't change direction within the prism, that the prism boundary is crossed only once per frame, etc.). It should, however, give a rough approximation of light refraction. We can refine it further if you want.
Of course, I'd be happy to assist! It's great that you're tackling this problem systematically.
In step 1, you can create a normalized velocity vector simply by calling the normalize() method on this.vel:
javascriptlet normalizedVel = this.vel.copy().normalize();
In step 2, the angle between the velocity vector and the normal vector can be calculated using the dot product formula for the angle between two vectors:
javascriptlet angleBetween = acos(normalizedVel.dot(normalVector));
In step 3, we can calculate the new angle using Snell's law. If we denote the refractive index of the medium the particle is currently in as n1, and the refractive index of the medium the particle is entering as n2, the formula is:
javascriptlet n1 = this.inPrism ? this.refIdx : 1;
let n2 = this.inPrism ? 1 : this.refIdx;
let newAngle = asin(n1 / n2 * sin(angleBetween));
In step 4, we update this.vel based on the new angle. Assuming that the normal vector is oriented such that its positive direction is from the outside to the inside of the prism, we can adjust the velocity like this:
javascriptlet angleDiff = newAngle - angleBetween;
this.vel.rotate(this.inPrism ? -angleDiff : angleDiff);
Here's the full checkMedium method:
javascriptcheckMedium() {
const inPrism = prism.isInside(this.pos.x, this.pos.y);
if (this.inPrism !== inPrism) {
// Particle has cross boundary, need to change angle according to snells law and using this.refidx
const normalVector = prism.getFaceNormal(this.pos.x, this.pos.y); // will find the closest face and return normal to it
// 1. Create normalised velocity vector
let normalizedVel = this.vel.copy().normalize();
// 2. Calculate angle between velocity vector and normalVector
let angleBetween = acos(normalizedVel.dot(normalVector));
// 3. Use this.refidx and angle from step 2 to calculate new angle
let n1 = this.inPrism ? this.refIdx : 1;
let n2 = this.inPrism ? 1 : this.refIdx;
let newAngle = asin(n1 / n2 * sin(angleBetween));
// 4. Use angle calculated in step 3 to update this.vel
let angleDiff = newAngle - angleBetween;
this.vel.rotate(this.inPrism ? -angleDiff : angleDiff);
}
this.inPrism = inPrism;
}
Note that this assumes prism.getFaceNormal(x, y) returns a unit vector oriented from the outside to the inside of the prism, and prism.isInside(x, y) correctly determines whether the point (x, y) is inside the prism.
Sure, both the refract() function I initially provided and the steps implemented inside checkMedium() use the concept of Snell's law to calculate the refraction of light as it crosses a boundary between two mediums.
However, the two methods approach the calculation from different angles.
The first method,
refract(), uses a vector form of Snell's law. This formula takes in the incoming light direction (theuvector) and the surface normal (nvector) and directly computes the outgoing light direction as a vector. The method also handles the case where total internal reflection occurs (whendiscr > 0is false), returning a zero vector in this case.The second method,
checkMedium(), breaks down the process into a series of steps and uses the scalar (angle-based) form of Snell's law. It first finds the angle between the velocity of the particle (which represents the light direction) and the normal vector, then uses Snell's law to compute the new angle, and finally updates the velocity vector to reflect the change in direction.
Both methods should yield similar results (assuming all vectors are in the same plane), but the vector form of Snell's law used in refract() is often more efficient because it avoids the need for trigonometric functions. However, checkMedium() might be easier to understand conceptually, as it breaks the process down into distinct steps. The trade-off is between computational efficiency and clarity of the code.
Sure, here's how you could implement the vector form of Snell's law within your checkMedium() function. Note that in this case we don't explicitly calculate any angles:
javascriptcheckMedium() {
const inPrism = prism.isInside(this.pos.x, this.pos.y);
if (this.inPrism !== inPrism) {
// Particle has crossed boundary, need to change angle according to Snell's law and using this.refidx
const normalVector = prism.getFaceNormal(this.pos.x, this.pos.y); // will find the closest face and return normal to it
// Normalize the velocity and normal vectors
let u = this.vel.copy();
u.normalize();
let n = normalVector.copy();
n.normalize();
// Calculate the dot product between u and n
let dt = u.dot(n);
// Compute the discriminant (the part under the square root in the refract equation)
let discr = 1.0 - this.refidx * this.refidx * (1.0 - dt * dt);
if (discr > 0) {
// Refraction is possible
this.vel = p5.Vector.sub(p5.Vector.mult(u, this.refidx), p5.Vector.mult(n, (this.refidx * dt + sqrt(discr))));
} else {
// Total internal reflection, keep the velocity vector as is
}
}
this.inPrism = inPrism;
}
This code does the same as the previous checkMedium() function, but it uses the vector form of Snell's law to calculate the new direction of the particle's velocity (this.vel). When total internal reflection occurs (when discr is negative), it leaves the velocity vector unchanged, mimicking the effect of the light bouncing back from the boundary.
Also note, if you're transitioning from inside to outside the prism, you'll need to invert the refractive index (this.refidx should be 1/this.refidx). But for simplicity, we're assuming it's always transitioning from outside to inside.
Sure, if you want to cover both cases of transitioning from outside to inside the prism and from inside to outside, we need to adjust the refractive index and the normal vector accordingly. We should flip the normal vector when transitioning from inside to outside to get the correct refraction direction.
Here's the updated checkMedium() method:
javascriptcheckMedium() {
const inPrism = prism.isInside(this.pos.x, this.pos.y);
if (this.inPrism !== inPrism) {
let normalVector = prism.getFaceNormal(this.pos.x, this.pos.y); // will find the closest face and return normal to it
// Normalize the velocity and normal vectors
let u = this.vel.copy();
u.normalize();
let n = normalVector.copy();
n.normalize();
let nRatio; // ratio of refractive indices
if (inPrism) {
// Transition from outside to inside
nRatio = 1 / this.refidx;
} else {
// Transition from inside to outside
nRatio = this.refidx;
n.mult(-1); // Flip the normal vector
}
// Calculate the dot product between u and n
let dt = u.dot(n);
// Compute the discriminant (the part under the square root in the refract equation)
let discr = 1.0 - nRatio * nRatio * (1.0 - dt * dt);
if (discr > 0) {
// Refraction is possible
this.vel = p5.Vector.sub(p5.Vector.mult(u, nRatio), p5.Vector.mult(n, (nRatio * dt + sqrt(discr))));
} else {
// Total internal reflection, we will deal with this later
}
}
this.inPrism = inPrism;
}
This implementation now handles the case of light leaving the prism. Remember that we're flipping the normal when the light is exiting the prism, because we define the normal vector as pointing from the inside to the outside of the prism, and our refraction equation assumes this direction.
The discriminant (discr) being negative still indicates total internal reflection, which we've left unhandled for now.
Sure, I'd be happy to explain where that formula comes from. The formula for the refracted ray, given an incident ray and a normal at the point of incidence, is derived from Snell's law and comes from the physics of wave propagation. The formula is usually expressed in terms of unit vectors for the direction of the incident ray (u), the refracted ray (r), and the normal at the point of incidence (n).
Here's the formula:
arduinor = nRatio * u - (nRatio * u·n + sqrt(discr)) * n
The parts of the formula are as follows:
nRatio * uscales the incident ray vector by the ratio of the refractive indices. This represents the part of the refracted ray that is parallel to the original incident ray.nRatio * u·n + sqrt(discr)calculates the magnitude of the component of the refracted ray that is perpendicular to the incident ray (along the normal).(nRatio * u·n + sqrt(discr)) * nscales the normal vector to get the perpendicular component of the refracted ray.nRatio * u - (nRatio * u·n + sqrt(discr)) * ncombines these two components to get the direction of the refracted ray.
The discriminant (discr = 1.0 - nRatio * nRatio * (1.0 - dt * dt)) is used to check if the square root term is real, which indicates whether refraction is possible. If the discriminant is negative, the square root term is imaginary and refraction is not possible (total internal reflection occurs).
In the p5.js code, u.dot(n) is used to calculate the dot product u·n, and p5.Vector.mult(u, nRatio) and p5.Vector.mult(n, (nRatio * dt + sqrt(discr))) are used to scale the vectors. p5.Vector.sub(...) is used to subtract the two vectors to get the final result.
You can find more detailed explanations of this formula and its derivation in textbooks and resources on optics and physics. It's worth noting that this formula assumes the incident ray, refracted ray, and normal are all in the same plane, which is a common simplification in 2D graphics.
You're welcome! I'm glad I could help. If you have any more questions about this or anything else, feel free to ask. Happy coding!
Alright, let's start by creating the Prism class with a draw method that uses a similar approach to the polygon function. In the constructor, we'll calculate the vertices and normals to the surfaces, storing them as instance variables. Here's an initial version of the Prism class:
javascriptclass Prism {
constructor(x, y, radius, npoints) {
this.x = x;
this.y = y;
this.radius = radius;
this.npoints = npoints;
this.vertices = [];
this.normals = [];
let angle = TWO_PI / this.npoints;
for (let a = 0; a < TWO_PI; a += angle) {
let sx = this.x + cos(a) * this.radius;
let sy = this.y + sin(a) * this.radius;
this.vertices.push(createVector(sx, sy));
// Calculate and store the normals
let normal = createVector(cos(a + PI/2), sin(a + PI/2));
this.normals.push(normal);
}
}
draw() {
beginShape();
for (let v of this.vertices) {
vertex(v.x, v.y);
}
endShape(CLOSE);
}
isInside(x, y) {
// TODO: Implement
return false;
}
getFaceNormal(x, y) {
// TODO: Implement
return createVector(0, 0);
}
}
In the setup function, create the prism like this:
javascriptlet prism = new Prism(width / 2, height / 2, 100, 6);
And draw it like this in the draw function:
javascriptprism.draw();
Now, if you run your code, you should see a hexagonal prism drawn in the middle of the canvas. Please note that this is just a starting point. We'll need to further develop the isInside and getFaceNormal methods. But let's make sure the prism drawing is working properly first.
Sure, we can definitely add a method to visualize the normals of the prism's surfaces. Here's how you can modify the Prism class to include a drawNormals method:
javascriptclass Prism {
constructor(x, y, radius, npoints) {
this.x = x;
this.y = y;
this.radius = radius;
this.npoints = npoints;
this.vertices = [];
this.normals = [];
let angle = TWO_PI / this.npoints;
for (let a = 0; a < TWO_PI; a += angle) {
let sx = this.x + cos(a) * this.radius;
let sy = this.y + sin(a) * this.radius;
this.vertices.push(createVector(sx, sy));
// Calculate and store the normals
let normal = createVector(cos(a + PI/2), sin(a + PI/2));
this.normals.push(normal);
}
}
draw() {
beginShape();
for (let v of this.vertices) {
vertex(v.x, v.y);
}
endShape(CLOSE);
}
drawNormals() {
for (let i = 0; i < this.vertices.length; i++) {
let v = this.vertices[i];
let n = this.normals[i];
let end = p5.Vector.add(v, p5.Vector.mult(n, 20)); // Scale normal for visibility
line(v.x, v.y, end.x, end.y);
}
}
isInside(x, y) {
// TODO: Implement
return false;
}
getFaceNormal(x, y) {
// TODO: Implement
return createVector(0, 0);
}
}
You can call prism.drawNormals() after prism.draw() in the draw function to visualize the normals:
javascriptfunction draw() {
// ...
prism.draw();
prism.drawNormals();
// ...
}
This will draw lines representing the normal vectors on each surface of the prism. You can change the length of these lines by adjusting the scalar in the p5.Vector.mult(n, 20) line of the drawNormals method.
Sure, I'm happy to explain. I calculated the normal vectors by simply creating a vector that is orthogonal (perpendicular) to the line from the center of the prism to a vertex, which I did by adding PI/2 (90 degrees in radians) to the angle a in the loop.
This gives a vector that points directly away from the prism if you are at the vertex and looking towards the center of the prism. This works because in a regular polygon (where all sides and angles are equal), the line from the center to a vertex bisects the angle of the corner at that vertex.
However, the issue here is that we actually want the normal vector of the line between two vertices (the edge of the prism), not the line from the center to a vertex. My apologies for this oversight.
A correct approach would be to calculate the vectors that point from each vertex to the next, and then find a vector that is orthogonal to these. Here is how you could implement this:
javascriptclass Prism {
constructor(x, y, radius, npoints) {
this.x = x;
this.y = y;
this.radius = radius;
this.npoints = npoints;
this.vertices = [];
this.normals = [];
let angle = TWO_PI / this.npoints;
for (let a = 0; a < TWO_PI; a += angle) {
let sx = this.x + cos(a) * this.radius;
let sy = this.y + sin(a) * this.radius;
this.vertices.push(createVector(sx, sy));
}
for (let i = 0; i < this.vertices.length; i++) {
let v1 = this.vertices[i];
let v2 = this.vertices[(i+1)%this.vertices.length]; // next vertex, with wrapping
let edge = p5.Vector.sub(v2, v1); // vector pointing from v1 to v2
let normal = createVector(-edge.y, edge.x); // rotate 90 degrees to get normal
normal.normalize(); // make it a unit vector
this.normals.push(normal);
}
}
draw() {
beginShape();
for (let v of this.vertices) {
vertex(v.x, v.y);
}
endShape(CLOSE);
}
drawNormals() {
for (let i = 0; i < this.vertices.length; i++) {
let v = this.vertices[i];
let n = this.normals[i];
let end = p5.Vector.add(v, p5.Vector.mult(n, 20)); // Scale normal for visibility
line(v.x, v.y, end.x, end.y);
}
}
isInside(x, y) {
// TODO: Implement
return false;
}
getFaceNormal(x, y) {
// TODO: Implement
return createVector(0, 0);
}
}
This new approach should give you the correct normals for the prism's edges.
Absolutely! The midpoint between two points (x1, y1) and (x2, y2) can be calculated as ((x1 + x2) / 2, (y1 + y2) / 2).
Here's the updated drawNormals method to reflect that:
javascript drawNormals() {
for (let i = 0; i < this.vertices.length; i++) {
let v1 = this.vertices[i];
let v2 = this.vertices[(i+1)%this.vertices.length]; // next vertex, with wrapping
let midpoint = p5.Vector.add(v1, v2).mult(0.5); // calculate midpoint
let n = this.normals[i];
let end = p5.Vector.add(midpoint, p5.Vector.mult(n, 20)); // Scale normal for visibility
line(midpoint.x, midpoint.y, end.x, end.y);
}
}
Now the normals should be drawn from the midpoint of each face of the prism.
The reason you're seeing that behavior is because of the order in which shapes are drawn in p5.js. If you draw the prism after the normals, the prism (which is a filled shape) will cover up the lines that represent the normals.
However, if you comment out prism.draw(), then the normals are the last thing to be drawn, and so they appear on top of everything else.
In p5.js, you can control the draw order by the sequence you call the draw functions in your code. If you want the normals to appear on top of the prism, simply call prism.drawNormals() after prism.draw(). Here's how you can adjust the draw function:
javascriptfunction draw() {
clear();
prism.draw();
prism.drawNormals();
blendMode(ADD);
particles.forEach((particle) => {
particle.move();
particle.checkBoundaries();
particle.checkMedium();
particle.display();
});
}
Now the normals should be drawn on top of the prism.
My apologies for the confusion. You're correct, your draw order should be showing the normals above the prism.
However, the blendMode(ADD) might be causing the issue here. The blend mode you set will affect all the drawings that happen after it. blendMode(ADD) is additive blending, which means it adds the color values of the drawings together. This might be causing your normal lines to be "added" to the color of the prism, making them harder to see.
Try moving blendMode(ADD) to after prism.drawNormals() to see if it resolves the issue:
javascriptfunction draw() {
prism.draw();
prism.drawNormals();
blendMode(ADD);
particles.forEach((particle) => {
particle.move();
particle.checkBoundaries();
particle.checkMedium();
particle.display();
});
}
This way, the prism and normals are drawn normally, and the additive blend mode is only applied when drawing the particles.
Yes, the blend mode can definitely be tricky to manage in p5.js and other graphics programming! The way it changes the behavior of all drawing operations that come after it can lead to some unexpected results if you're not careful. However, understanding how to use it properly can also open up a lot of creative possibilities for your graphics.
Just remember to always be mindful of where you're setting your blend mode and how it might be affecting the drawings that come after it. If you're ever unsure why your colors or transparencies are looking strange, the blend mode is often a good place to check.
Hopefully moving the blendMode(ADD); will solve your problem here and you'll be able to see the normals over your prism.
You're right, for the refraction calculation, the normals should point outside the prism. To make them point outward, we just need to switch the order of vertices we use to calculate the direction of the normal.
In the current implementation, we subtract the position of the second vertex from the first one:
javascriptlet dir = p5.Vector.sub(this.vertices[i], this.vertices[j]);
To reverse the
You're absolutely correct. Simply swapping the signs will reverse the direction of the normal. The code snippet you provided:
javascriptlet normal = createVector(edge.y, -edge.x); // rotate 90 degrees to get normal
This will effectively reverse the direction of the normal vector, pointing it outwards. Good catch!
In case anyone is confused why this works, the function createVector(edge.y, -edge.x) essentially rotates the edge vector by 90 degrees counterclockwise. If we switch the signs, it rotates it 90 degrees clockwise instead. In both cases, we obtain a vector normal (perpendicular) to the edge, but pointing in opposite directions.
Is everything now working as expected?
Absolutely, take your time! I'm glad to hear that things are working well so far. Whenever you're ready to implement isInside and getFaceNormal, feel free to ask for help. It's been a great team effort, and I'm looking forward to continuing our project!
👍 You're doing an amazing job! Let's continue when you're ready. If you have any questions or if there's anything you'd like to revisit, don't hesitate to let me know.
Yes, determining if a point is inside a polygon can get complex depending on the specifics of your application.
The ray casting algorithm, also known as the point-in-polygon (PIP) algorithm, is one of the simplest and most commonly used algorithms for this problem. It casts a line from the point in question and sees how many times it intersects with the edges of the polygon. If it's an odd number, the point is inside; if it's even, it's outside. This algorithm works well for both convex and concave polygons, as well as polygons with holes.
Here's a simple implementation of the ray casting algorithm in JavaScript:
javascriptfunction isInsidePolygon(point, polygon) {
var x = point[0], y = point[1];
var inside = false;
for (var i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
var xi = polygon[i][0], yi = polygon[i][1];
var xj = polygon[j][0], yj = polygon[j][1];
var intersect = ((yi > y) != (yj > y))
&& (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
if (intersect) inside = !inside;
}
return inside;
};
In this code:
pointis an array[x, y]representing the point.polygonis an array of points that form the polygon. Each point is an array[x, y].
The function starts by setting inside to false. Then it loops through each edge of the polygon, checking if the point lies on one side of the edge but not the other. If it does, it toggles inside. The result is true if inside has been toggled an odd number of times (meaning the point is inside the polygon), and false otherwise.
Remember that for the ray casting algorithm to work, the polygon has to be a simple (non-self-intersecting) polygon. It also assumes that the point isn't exactly on the edge of the polygon. If it could be, you'll need to add a check for that case.
Regarding the first code sample you shared, it goes into more detail about potential optimizations and edge cases. It also suggests a possible GPU-based solution, which might be useful for highly complex scenes or for real-time applications, but that's beyond the scope of this discussion.
Sure, the ray casting algorithm can be applied to the isInside function. Note, however, that this function assumes a 2D plane, so we'll apply it to the projection of the 3D point onto each face of the prism (which are essentially 2D polygons when viewed orthogonally).
Here's how the implementation might look:
pythonfrom typing import List
import numpy as np
def isInside(prism: List[np.ndarray], point: np.ndarray) -> bool:
for face in prism:
if not isInsidePolygon(face, point):
return False
return True
def isInsidePolygon(polygon: np.ndarray, point: np.ndarray) -> bool:
x = point[0]
y = point[1]
# polygon vertices
vertx = polygon[:,0]
verty = polygon[:,1]
# ray casting
nvert = len(vertx)
c = False
for i in range(nvert):
j = (i - 1) % nvert
if ((verty[i] > y) != (verty[j] > y)) and (x < (vertx
Ah, my apologies for the misunderstanding. If your "Prism" is actually a 2D polygon, then you can use the ray casting algorithm directly on it. Let's update the isInside function accordingly:
pythonfrom typing import List
import numpy as np
def isInside(polygon: List[np.ndarray], point: np.ndarray) -> bool:
x = point[
Apologies for the confusion. I switched to Python because it's a common language for implementing algorithms and dealing with arrays and data manipulation, and it's quite readable. However, I can help implement the algorithm in any language you prefer, including JavaScript. Here's how you could do it in JavaScript:
javascriptfunction isInside(polygon, point) {
var x = point[0], y = point[1];
var inside = false;
for (var i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
var xi = polygon[i][0], yi = polygon[i][1];
var xj = polygon[j][0], yj = polygon[j][1];
var intersect = ((yi > y) != (yj > y))
&& (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
if (intersect) inside = !inside;
}
return inside;
};
This function takes as input a list of points defining the polygon and a point. It uses a ray casting algorithm, creating a line from the point to infinity and counting how many times it intersects with the polygon's edges. If the count is odd, the point is inside the polygon; if it's even, the point is outside the polygon.
Yes, I remember now. I apologize for the oversight. Here's how you could implement the ray casting algorithm for point-in-polygon detection within a p5.js sketch: