D3 Examples - WebGL version of "Interstellar Overdrive"

WebGL version of "Interstellar Overdrive"
An animated version of this generative art pop up on my twitter feed and it caught my eye. The original was created in Processing and each frame saved to a PNG file, so I decided to create a browser-based version in d3.
I started with a straightforward d3 and canvas port, to understand what the code was doing. With ~24k points, this version had a poor framerate and wasn't satisfying to watch. The WebGL port, on the other hand, proved much more challanging (this was my first attempt at using WebGL) but with very pleasing results.
A few helpful links I gathered along the way:
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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script language="javascript" src="https://npmcdn.com/regl/dist/regl.js"></script>
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <script src="https://d3js.org/d3-random.v1.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>
​
<body>
  <div id="art"></div>
  <script type="text/javascript">
        // based on https://deconbatch.blogspot.com/2017/12/interstellar-overdrive.html
​
        const numPoints = 360*68;
        var width = isNaN(window.innerWidth) ? window.clientWidth : window.innerWidth,
            height = isNaN(window.innerHeight) ? window.clientHeight : window.innerHeight;
        const pixelRatio = width/height;
        const sizeBase = Math.max(width,height) / 64.;
​
        if (isNaN(width) || width==0) {
            width = 960; height=500;
        }
​
        var c = d3.select('#art').append("canvas")
                .attr('width', width)
                .attr('height', height);
        var canvas = c.node();
​
        function main(err, regl) {
            
            var scaleDivBase = d3.scaleLinear().domain([0.0, 1.0]).range([0.00005, 0.00025]);
            var scale360     = d3.scaleLinear().domain([0.0, 1.0]).range([0, 360.0]);
            var scaleRadius  = d3.scaleLinear().range([1.0, 1.6]).domain([-2.0, 2.0]);
            var scaleXY = d3.scaleLinear().domain([-1.0, 1.0]);
​
            var rnd = d3.randomUniform(1.0);
​
            // pick a random color
            const colorBase = d3.randomUniform(360.0)();
            const col = d3.color('hsl(' + colorBase + ', 60%, 40%)').rgb();
            const colorArray = [col.r/256., col.g/256., col.b/256.];
                
            var cxnoiseDivBase = scaleDivBase(rnd());
            var cynoiseBase = scale360(rnd());
            var csnoiseBase = scale360(rnd());
            
            function radians(degrees) {
                return degrees * Math.PI / 180.0;
            }
​
            // function to compile a draw points regl func
            function createDrawPoints(points) {
                const drawPoints = regl({
                    frag: `
                        #ifdef GL_OES_standard_derivatives
                        #extension GL_OES_standard_derivatives : enable
                        #endif
​
                        // set the precision of floating point numbers
                        precision mediump float;
​
                        // these values are populated by the vertex shader
                        varying vec3 fragColor;
                        varying float fragAlpha;
                    
​
                        void main() {
​
                            // make our points look like circles
                            float r = 0.0, delta = 0.0, alpha = 1.0;
                            vec2 cxy = 2.0 * gl_PointCoord - 1.0;
                            r = dot(cxy, cxy);
​
                            // soften the edges a bit
                            #ifdef GL_OES_standard_derivatives
                                delta = fwidth(r);
                                alpha = 0.9 - smoothstep(1.0 - delta, 1.0 + delta, r);
                            #endif
​
                            if (r > 1.0) {
                                discard;
                            }
​
                            gl_FragColor = vec4(fragColor, fragAlpha * alpha);
                        }
                    `,
​
                    vert: `
                        // per vertex attributes
                        attribute vec2 position;
                        attribute float idx;
                        
                        // variables to send to the fragment shader
                        varying vec3 fragColor;
                        varying float fragAlpha;
                        
                        // values that are the same for all vertices
                        uniform float stageWidth;
                        uniform float stageHeight;
                        uniform float t;    //time
                        uniform vec3 noiseBase;
                        uniform float sizeBase;
                        uniform float numPoints;
                        uniform vec3 color;
                        
                        // helper function to transform from pixel space to normalized device coordinates (NDC)
                        // in NDC (0,0) is the middle, (-1, 1) is the top left and (1, -1) is the bottom right.
                        vec2 normalizeCoords(vec2 position, float rotation) {
                            
                            // compute rotation matrix
                            float pixelRatio = stageHeight / stageWidth;
                            float c = cos(rotation);
                            float s = sin(rotation);
                            mat2 r = mat2(c, -s * pixelRatio, s, c * pixelRatio);
​
                            // read in the positions into x and y vars
                            float x = position[0];
                            float y = position[1];
​
                            // norm to device coords
                            vec2 v = vec2(
                                2.0 * ((x / stageWidth) - 0.5),
                                // invert y since we think [0,0] is bottom left in pixel space
                                -(2.0 * ((y / stageHeight) - 0.5)));
                            
                            // center
                            v = v + vec2(1., -1.);
                            
                            // apply rotation
                            return v * r;
                        }
​
                        // noise helper function
                        vec3 customNoise(vec3 value) { 
                            vec3 s = sin(value);
                            return (s*s*s) * cos(value*value);
                        }
​
                        // helper function that is the equivilant of processing's map function
                        float map(float value, float istart, float istop, float ostart,float ostop) {
                            return ostart + (ostop - ostart) * ((value - istart) / (istop - istart));
                        }
​
                        // helper function that applies map to both elements of a vector
                        vec2 map(vec2 value, float istart, float istop, float ostart,float ostop) {
                            return ostart + (ostop - ostart) * ((value - istart) / (istop - istart));
                        }
​
                        void main() {  
​
                            // compute noise-vector @ time t = x, y, s
                            vec3 custNoise = customNoise(noiseBase + vec3(
                                (idx)          * t*0.00000001,       //wave
                                (1.+idx)*0.01  + t*0.0000015,        //roll
                                (1.+idx)*0.005 + t*0.000005          //blink
                            ));   
​
                            // calculate x/y coords based on the noise function
                            float radius = (15.0 + (idx * 0.02)) * map(custNoise[0] + custNoise[1], -2.0, 2.0, 1.0, 1.6);
                            vec2 ePt = map(position, -1., 1., -radius, radius);
                            
                            // send color and alpha to the fragment shader
                            fragColor = color;
                            fragAlpha = 1. - abs(custNoise[2]) + 0.1;
                       
                            // set position and point size
                            gl_Position = vec4(normalizeCoords(ePt, radians(t/200.)), 0, 1.0);
                            gl_PointSize = (2.0 + abs(custNoise[2]) * sizeBase) * map(idx, 0.0, numPoints, 0.15, 1.5);
                        
                        }
                    `,
                    
                    attributes: {
                        position: points.map(d => [Math.cos(d.rads), Math.sin(d.rads)]),
                        idx: points.map(d => d.idx)
                    },
​
                    uniforms: {
                        stageWidth: regl.prop('stageWidth'),
                        stageHeight: regl.prop('stageHeight'),
                        color: regl.prop('color'),
                        noiseBase: regl.prop('noiseBase'),
                        sizeBase: regl.prop('sizeBase'),
                        numPoints: regl.prop('numPoints'),                        
                        t: ({ time }) => time * 1000,
                    },
                    blend: {
                        enable: true,
                        func: { srcRGB: 'src alpha', dstRGB: 'one minus src alpha', srcAlpha: 1, dstAlpha: 'one minus src alpha' }, //1                        
                    },
                    // specify the number of points to draw
                    count: points.length,
                    
                    // specify that each vertex is a point (not part of a mesh)
                    primitive: 'points',
                });
​
                return drawPoints;
            }
​
            // function to start the animation loop
            function animate(points) {
                
                // setup the regl program
                const drawPoints = createDrawPoints(points);
​
                // start an animation loop
                const frameLoop = regl.frame(({ time }) => {
                    
                    regl.clear({color: [1.,1.,1.,1.], depth: 1});
​
                    // draw the points using our created regl func
                    drawPoints({
                        stageWidth: width,
                        stageHeight: height,
                        noiseBase: [cxnoiseDivBase, cynoiseBase, csnoiseBase],
                        color: colorArray,
                        sizeBase: sizeBase,
                        numPoints: numPoints
                    });       
​
                });
            }
​
            // create initial set of points
            const points = d3.range(numPoints).map(i => ({
                rads: radians(i*0.1),
                idx: i
            }));
            
            // start the initial animation
            animate(points);
        }
​
        var regl = createREGL({
            extensions: ['OES_standard_derivatives'],
            canvas: canvas,
            attributes: {
                alpha: false,
                depth: false,
                antialias: true
            },
            onDone: main
        });
​
    </script>
</body>
​
​
    