Computer Graphics & Visualization @ufrj.br
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Ray marching
{
let n = 256;
let r = 100;
let cx = n / 2,
cy = n / 2;
let ctx = DOM.context2d(n, n, 1);
yield ctx.canvas;
for (let x = 0; x < n; x++) {
for (let y = 0; y < n; y++) {
let dist = Math.sqrt((x - cx) ** 2 + (y - cy) ** 2) - r;
let gray = ~~(n - Math.abs(dist));
ctx.fillStyle =
dist < 0 ? `rgb(${gray},0,0)` : `rgb(${gray},${gray},${gray})`;
ctx.fillRect(x, y, 1, 1);
}
}
return ctx.canvas;
}
//
// Creates a canvas and runs a WebGL program that draws two triangles covering the whole canvas, where
// the fragment processing is performed by 'shader', which should be valid fragment shader code.
// Some useful uniforms are automaticlly passed to the shader:
// . u_resolution, a vec2 containing the width and height of the canvas.
// . u_mouse, a vec2 containing the position of the mouse in the canvas.
// . u_frame, an int containing the number of frames rendered so far.
// By default, the canvas is rendered a single time and once again for each click or drag of the mouse.
toy = function (shader, options = {}) {
let { width = 512, height = 512, render = "onmouse" } = options;
let canvas = DOM.canvas(width, height);
let regl = createRegl({
canvas
});
let uniforms = {
u_resolution: [width, height],
u_frame: 0,
u_mouse: [0, 0]
};
let draw = regl({
frag:
`
precision mediump float;
uniform vec2 u_resolution;
uniform int u_frame;
uniform vec2 u_mouse;
` + shader,
vert: `
attribute vec2 position;
void main () {
gl_Position = vec4(position, 0, 1);
}`,
attributes: {
position: [
[-1, -1],
[1, -1],
[1, 1],
[1, 1],
[-1, 1],
[-1, -1]
]
},
uniforms: {
u_resolution: regl.prop("u_resolution"),
u_frame: regl.prop("u_frame"),
u_mouse: regl.prop("u_mouse")
},
count: 6
});
let requestId = null;
function renderFrame() {
uniforms.u_frame++;
draw(uniforms);
}
canvas.onmousedown = (e) => {
uniforms.u_mouse = [e.offsetX, height - e.offsetY];
if (render != "single") renderFrame();
};
canvas.onmousemove = (e) => {
uniforms.u_mouse = [e.offsetX, height - e.offsetY];
if (render != "single" && e.buttons != 0) renderFrame();
};
invalidation.then(() => {
if (requestId) cancelAnimationFrame(requestId);
});
canvas.value = shader;
if (render == "continuous") {
function animationRender() {
renderFrame();
requestId = requestAnimationFrame(animationRender);
}
animationRender();
} else {
renderFrame();
}
return canvas;
}
// TODO: Incorporate a player bar!
import {select} from "@jashkenas/inputs"
createRegl = require('regl@1.4.2/dist/regl.js')
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