main.js

'use strict';

const canvas = document.getElementsByTagName('canvas')[0];

canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;

const config = {
    TEXTURE_DOWNSAMPLE: 1,
    DENSITY_DISSIPATION: 0.98,
    VELOCITY_DISSIPATION: 0.99,
    PRESSURE_DISSIPATION: 0.8,
    PRESSURE_ITERATIONS: 25,
    CURL: 30,
    SPLAT_RADIUS: 0.005
};

let pointers = [];
let splatStack = [];

let _getWebGLContext = getWebGLContext(canvas);
let gl = _getWebGLContext.gl;
let ext = _getWebGLContext.ext;
let support_linear_float = _getWebGLContext.support_linear_float;

function getWebGLContext(canvas) {
    const params = {
        alpha: false,
        depth: false,
        stencil: false,
        antialias: false
    };

    let gl = canvas.getContext('webgl2', params);

    let isWebGL2 = !!gl;

    if (!isWebGL2) gl = canvas.getContext('webgl', params) || canvas.getContext('experimental-webgl', params);

    let halfFloat = gl.getExtension('OES_texture_half_float');
    let support_linear_float = gl.getExtension('OES_texture_half_float_linear');

    if (isWebGL2) {
        gl.getExtension('EXT_color_buffer_float');
        support_linear_float = gl.getExtension('OES_texture_float_linear');
    }

    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    let internalFormat = isWebGL2 ? gl.RGBA16F : gl.RGBA;
    let internalFormatRG = isWebGL2 ? gl.RG16F : gl.RGBA;
    let formatRG = isWebGL2 ? gl.RG : gl.RGBA;
    let texType = isWebGL2 ? gl.HALF_FLOAT : halfFloat.HALF_FLOAT_OES;

    return {
        gl: gl,
        ext: {
            internalFormat: internalFormat,
            internalFormatRG: internalFormatRG,
            formatRG: formatRG,
            texType: texType
        },
        support_linear_float: support_linear_float
    };
}

function PointerPrototype() {
    this.id = -1;
    this.x = 0;
    this.y = 0;
    this.dx = 0;
    this.dy = 0;
    this.down = false;
    this.moved = false;
    this.color = [30, 0, 300];
}

pointers.push(new PointerPrototype());

let GLProgram = function () {

    function GLProgram(vertexShader, fragmentShader) {

        if (!(this instanceof GLProgram))
            throw new TypeError("Cannot call a class as a function");

        this.uniforms = {};
        this.program = gl.createProgram();

        gl.attachShader(this.program, vertexShader);
        gl.attachShader(this.program, fragmentShader);
        gl.linkProgram(this.program);

        if (!gl.getProgramParameter(this.program, gl.LINK_STATUS)) throw gl.getProgramInfoLog(this.program);

        let uniformCount = gl.getProgramParameter(this.program, gl.ACTIVE_UNIFORMS);

        for (let i = 0; i < uniformCount; i++) {

            let uniformName = gl.getActiveUniform(this.program, i).name;

            this.uniforms[uniformName] = gl.getUniformLocation(this.program, uniformName);

        }
    }

    GLProgram.prototype.bind = function bind() {
        gl.useProgram(this.program);
    };

    return GLProgram;

}();

function compileShader(type, source) {
    let shader = gl.createShader(type);

    gl.shaderSource(shader, source);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) throw gl.getShaderInfoLog(shader);

    return shader;
}

let baseVertexShader = compileShader(gl.VERTEX_SHADER, 'precision highp float; precision mediump sampler2D; attribute vec2 aPosition; varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB; uniform vec2 texelSize; void main () {     vUv = aPosition * 0.5 + 0.5;     vL = vUv - vec2(texelSize.x, 0.0);     vR = vUv + vec2(texelSize.x, 0.0);     vT = vUv + vec2(0.0, texelSize.y);     vB = vUv - vec2(0.0, texelSize.y);     gl_Position = vec4(aPosition, 0.0, 1.0); }');
let clearShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; uniform sampler2D uTexture; uniform float value; void main () {     gl_FragColor = value * texture2D(uTexture, vUv); }');
let displayShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; uniform sampler2D uTexture; void main () {     gl_FragColor = texture2D(uTexture, vUv); }');
let splatShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; uniform sampler2D uTarget; uniform float aspectRatio; uniform vec3 color; uniform vec2 point; uniform float radius; void main () {     vec2 p = vUv - point.xy;     p.x *= aspectRatio;     vec3 splat = exp(-dot(p, p) / radius) * color;     vec3 base = texture2D(uTarget, vUv).xyz;     gl_FragColor = vec4(base + splat, 1.0); }');
let advectionManualFilteringShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; uniform sampler2D uVelocity; uniform sampler2D uSource; uniform vec2 texelSize; uniform float dt; uniform float dissipation; vec4 bilerp (in sampler2D sam, in vec2 p) {     vec4 st;     st.xy = floor(p - 0.5) + 0.5;     st.zw = st.xy + 1.0;     vec4 uv = st * texelSize.xyxy;     vec4 a = texture2D(sam, uv.xy);     vec4 b = texture2D(sam, uv.zy);     vec4 c = texture2D(sam, uv.xw);     vec4 d = texture2D(sam, uv.zw);     vec2 f = p - st.xy;     return mix(mix(a, b, f.x), mix(c, d, f.x), f.y); } void main () {     vec2 coord = gl_FragCoord.xy - dt * texture2D(uVelocity, vUv).xy;     gl_FragColor = dissipation * bilerp(uSource, coord);     gl_FragColor.a = 1.0; }');
let advectionShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; uniform sampler2D uVelocity; uniform sampler2D uSource; uniform vec2 texelSize; uniform float dt; uniform float dissipation; void main () {     vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;     gl_FragColor = dissipation * texture2D(uSource, coord); }');
let divergenceShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB; uniform sampler2D uVelocity; vec2 sampleVelocity (in vec2 uv) {     vec2 multiplier = vec2(1.0, 1.0);     if (uv.x < 0.0) { uv.x = 0.0; multiplier.x = -1.0; }     if (uv.x > 1.0) { uv.x = 1.0; multiplier.x = -1.0; }     if (uv.y < 0.0) { uv.y = 0.0; multiplier.y = -1.0; }     if (uv.y > 1.0) { uv.y = 1.0; multiplier.y = -1.0; }     return multiplier * texture2D(uVelocity, uv).xy; } void main () {     float L = sampleVelocity(vL).x;     float R = sampleVelocity(vR).x;     float T = sampleVelocity(vT).y;     float B = sampleVelocity(vB).y;     float div = 0.5 * (R - L + T - B);     gl_FragColor = vec4(div, 0.0, 0.0, 1.0); }');
let curlShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB; uniform sampler2D uVelocity; void main () {     float L = texture2D(uVelocity, vL).y;     float R = texture2D(uVelocity, vR).y;     float T = texture2D(uVelocity, vT).x;     float B = texture2D(uVelocity, vB).x;     float vorticity = R - L - T + B;     gl_FragColor = vec4(vorticity, 0.0, 0.0, 1.0); }');
let vorticityShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB; uniform sampler2D uVelocity; uniform sampler2D uCurl; uniform float curl; uniform float dt; void main () {     float L = texture2D(uCurl, vL).y;     float R = texture2D(uCurl, vR).y;     float T = texture2D(uCurl, vT).x;     float B = texture2D(uCurl, vB).x;     float C = texture2D(uCurl, vUv).x;     vec2 force = vec2(abs(T) - abs(B), abs(R) - abs(L));     force *= 1.0 / length(force + 0.00001) * curl * C;     vec2 vel = texture2D(uVelocity, vUv).xy;     gl_FragColor = vec4(vel + force * dt, 0.0, 1.0); }');
let pressureShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB; uniform sampler2D uPressure; uniform sampler2D uDivergence; vec2 boundary (in vec2 uv) {     uv = min(max(uv, 0.0), 1.0);     return uv; } void main () {     float L = texture2D(uPressure, boundary(vL)).x;     float R = texture2D(uPressure, boundary(vR)).x;     float T = texture2D(uPressure, boundary(vT)).x;     float B = texture2D(uPressure, boundary(vB)).x;     float C = texture2D(uPressure, vUv).x;     float divergence = texture2D(uDivergence, vUv).x;     float pressure = (L + R + B + T - divergence) * 0.25;     gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0); }');
let gradientSubtractShader = compileShader(gl.FRAGMENT_SHADER, 'precision highp float; precision mediump sampler2D; varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB; uniform sampler2D uPressure; uniform sampler2D uVelocity; vec2 boundary (in vec2 uv) {     uv = min(max(uv, 0.0), 1.0);     return uv; } void main () {     float L = texture2D(uPressure, boundary(vL)).x;     float R = texture2D(uPressure, boundary(vR)).x;     float T = texture2D(uPressure, boundary(vT)).x;     float B = texture2D(uPressure, boundary(vB)).x;     vec2 velocity = texture2D(uVelocity, vUv).xy;     velocity.xy -= vec2(R - L, T - B);     gl_FragColor = vec4(velocity, 0.0, 1.0); }');

let textureWidth = void 0;
let textureHeight = void 0;
let density = void 0;
let velocity = void 0;
let divergence = void 0;
let curl = void 0;
let pressure = void 0;

initFramebuffers();

let clearProgram = new GLProgram(baseVertexShader, clearShader);
let displayProgram = new GLProgram(baseVertexShader, displayShader);
let splatProgram = new GLProgram(baseVertexShader, splatShader);
let advectionProgram = new GLProgram(baseVertexShader, support_linear_float ? advectionShader : advectionManualFilteringShader);
let divergenceProgram = new GLProgram(baseVertexShader, divergenceShader);
let curlProgram = new GLProgram(baseVertexShader, curlShader);
let vorticityProgram = new GLProgram(baseVertexShader, vorticityShader);
let pressureProgram = new GLProgram(baseVertexShader, pressureShader);
let gradienSubtractProgram = new GLProgram(baseVertexShader, gradientSubtractShader);

function initFramebuffers() {

    textureWidth = gl.drawingBufferWidth >> config.TEXTURE_DOWNSAMPLE;
    textureHeight = gl.drawingBufferHeight >> config.TEXTURE_DOWNSAMPLE;

    let iFormat = ext.internalFormat;
    let iFormatRG = ext.internalFormatRG;
    let formatRG = ext.formatRG;
    let texType = ext.texType;

    density = createDoubleFBO(0, textureWidth, textureHeight, iFormat, gl.RGBA, texType, support_linear_float ? gl.LINEAR : gl.NEAREST);
    velocity = createDoubleFBO(2, textureWidth, textureHeight, iFormatRG, formatRG, texType, support_linear_float ? gl.LINEAR : gl.NEAREST);
    divergence = createFBO(4, textureWidth, textureHeight, iFormatRG, formatRG, texType, gl.NEAREST);
    curl = createFBO(5, textureWidth, textureHeight, iFormatRG, formatRG, texType, gl.NEAREST);
    pressure = createDoubleFBO(6, textureWidth, textureHeight, iFormatRG, formatRG, texType, gl.NEAREST);

}

function createFBO(texId, w, h, internalFormat, format, type, param) {

    gl.activeTexture(gl.TEXTURE0 + texId);

    let texture = gl.createTexture();

    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, w, h, 0, format, type, null);

    let fbo = gl.createFramebuffer();

    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
    gl.viewport(0, 0, w, h);
    gl.clear(gl.COLOR_BUFFER_BIT);

    return [texture, fbo, texId];

}

function createDoubleFBO(texId, w, h, internalFormat, format, type, param) {

    let fbo1 = createFBO(texId, w, h, internalFormat, format, type, param);
    let fbo2 = createFBO(texId + 1, w, h, internalFormat, format, type, param);

    return {
        get first() {
            return fbo1;
        },
        get second() {
            return fbo2;
        },
        swap: function swap() {
            let temp = fbo1;

            fbo1 = fbo2;
            fbo2 = temp;
        }
    };

}

let blit = function () {

    gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2, 0, 2, 3]), gl.STATIC_DRAW);
    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
    gl.enableVertexAttribArray(0);

    return function (destination) {
        gl.bindFramebuffer(gl.FRAMEBUFFER, destination);
        gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
    };

}();

let lastTime = Date.now();

update();

function update() {

    resizeCanvas();

    let dt = Math.min((Date.now() - lastTime) / 1000, 0.016);
    lastTime = Date.now();

    gl.viewport(0, 0, textureWidth, textureHeight);

    if (splatStack.length > 0) {
        for (let m = 0; m < splatStack.pop(); m++) {

            let color = [Math.random() * 10, Math.random() * 10, Math.random() * 10];
            let x = canvas.width * Math.random();
            let y = canvas.height * Math.random();
            let dx = 1000 * (Math.random() - 0.5);
            let dy = 1000 * (Math.random() - 0.5);

            splat(x, y, dx, dy, color);
        }
    }

    advectionProgram.bind();
    gl.uniform2f(advectionProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.first[2]);
    gl.uniform1i(advectionProgram.uniforms.uSource, velocity.first[2]);
    gl.uniform1f(advectionProgram.uniforms.dt, dt);
    gl.uniform1f(advectionProgram.uniforms.dissipation, config.VELOCITY_DISSIPATION);
    blit(velocity.second[1]);
    velocity.swap();

    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.first[2]);
    gl.uniform1i(advectionProgram.uniforms.uSource, density.first[2]);
    gl.uniform1f(advectionProgram.uniforms.dissipation, config.DENSITY_DISSIPATION);
    blit(density.second[1]);
    density.swap();

    for (let i = 0, len = pointers.length; i < len; i++) {
        let pointer = pointers[i];

        if (pointer.moved) {
            splat(pointer.x, pointer.y, pointer.dx, pointer.dy, pointer.color);
            pointer.moved = false;
        }
    }

    curlProgram.bind();
    gl.uniform2f(curlProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);
    gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.first[2]);
    blit(curl[1]);

    vorticityProgram.bind();
    gl.uniform2f(vorticityProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);
    gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.first[2]);
    gl.uniform1i(vorticityProgram.uniforms.uCurl, curl[2]);
    gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
    gl.uniform1f(vorticityProgram.uniforms.dt, dt);
    blit(velocity.second[1]);
    velocity.swap();

    divergenceProgram.bind();
    gl.uniform2f(divergenceProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);
    gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.first[2]);
    blit(divergence[1]);

    clearProgram.bind();

    let pressureTexId = pressure.first[2];

    gl.activeTexture(gl.TEXTURE0 + pressureTexId);
    gl.bindTexture(gl.TEXTURE_2D, pressure.first[0]);
    gl.uniform1i(clearProgram.uniforms.uTexture, pressureTexId);
    gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE_DISSIPATION);
    blit(pressure.second[1]);
    pressure.swap();

    pressureProgram.bind();
    gl.uniform2f(pressureProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);
    gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence[2]);
    pressureTexId = pressure.first[2];
    gl.activeTexture(gl.TEXTURE0 + pressureTexId);

    for (let _i = 0; _i < config.PRESSURE_ITERATIONS; _i++) {
        gl.bindTexture(gl.TEXTURE_2D, pressure.first[0]);
        gl.uniform1i(pressureProgram.uniforms.uPressure, pressureTexId);
        blit(pressure.second[1]);
        pressure.swap();
    }

    gradienSubtractProgram.bind();
    gl.uniform2f(gradienSubtractProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);
    gl.uniform1i(gradienSubtractProgram.uniforms.uPressure, pressure.first[2]);
    gl.uniform1i(gradienSubtractProgram.uniforms.uVelocity, velocity.first[2]);
    blit(velocity.second[1]);
    velocity.swap();

    gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
    displayProgram.bind();
    gl.uniform1i(displayProgram.uniforms.uTexture, density.first[2]);
    blit(null);

    requestAnimationFrame(update);

}

function splat(x, y, dx, dy, color) {

    splatProgram.bind();
    gl.uniform1i(splatProgram.uniforms.uTarget, velocity.first[2]);
    gl.uniform1f(splatProgram.uniforms.aspectRatio, canvas.width / canvas.height);
    gl.uniform2f(splatProgram.uniforms.point, x / canvas.width, 1.0 - y / canvas.height);
    gl.uniform3f(splatProgram.uniforms.color, dx, -dy, 1.0);
    gl.uniform1f(splatProgram.uniforms.radius, config.SPLAT_RADIUS);
    blit(velocity.second[1]);
    velocity.swap();

    gl.uniform1i(splatProgram.uniforms.uTarget, density.first[2]);
    gl.uniform3f(splatProgram.uniforms.color, color[0] * 0.3, color[1] * 0.3, color[2] * 0.3);
    blit(density.second[1]);
    density.swap();

}

function resizeCanvas() {

    (canvas.width !== canvas.clientWidth || canvas.height !== canvas.clientHeight) && (canvas.width = canvas.clientWidth, canvas.height = canvas.clientHeight, initFramebuffers());

}

let count = 0;
let colorArr = [Math.random() + 0.2, Math.random() + 0.2, Math.random() + 0.2];

canvas.addEventListener('mousemove', function (e) {
    count++;

    if (count > 25) {
        colorArr = [Math.random() + 0.2, Math.random() + 0.2, Math.random() + 0.2];
        count = 0;
    }

    pointers[0].down = true;
    pointers[0].color = colorArr;
    pointers[0].moved = pointers[0].down;
    pointers[0].dx = (e.offsetX - pointers[0].x) * 10.0;
    pointers[0].dy = (e.offsetY - pointers[0].y) * 10.0;
    pointers[0].x = e.offsetX;
    pointers[0].y = e.offsetY;
});

canvas.addEventListener('touchmove', function (e) {

    e.preventDefault();

    let touches = e.targetTouches;

    count++;

    if (count > 25) {
        colorArr = [Math.random() + 0.2, Math.random() + 0.2, Math.random() + 0.2];
        count = 0;
    }

    for (let i = 0, len = touches.length; i < len; i++) {
        if (i >= pointers.length) pointers.push(new PointerPrototype());

        pointers[i].id = touches[i].identifier;
        pointers[i].down = true;
        pointers[i].x = touches[i].pageX;
        pointers[i].y = touches[i].pageY;
        pointers[i].color = colorArr;

        let pointer = pointers[i];

        pointer.moved = pointer.down;
        pointer.dx = (touches[i].pageX - pointer.x) * 10.0;
        pointer.dy = (touches[i].pageY - pointer.y) * 10.0;
        pointer.x = touches[i].pageX;
        pointer.y = touches[i].pageY;
    }
}, false);