Holi Themed Design

 <canvas></canvas>

 <div>Happy Holi Everyone!</div>

 <p>(CLICK ON BLANK SPACES TO CHANGE COLOR)</P>

</body>

html, body {

    overflow: hidden;

    padding:50px;

    color:#fff;

}

 canvas {

    position: fixed;

    top:0;

    left:0;

    width:100%;

    height:100%;

    z-index:0.5;

    opacity:1;

}

div{

    position:relative;

    z-index:1;

    font-size:70px;

    padding:0;

    display: table;

    margin:auto;

    letter-spacing:2px;

    font-family: “Madimi One”, sans-serif;

}

P{

    display: table;

    margin:20px auto;

    font-family:Arial, Helvetica, sans-serif;

    text-align:center;

    font-size:8px;

    letter-spacing:2px;

    position:absolute;

    bottom:10px;

    left:50%;  

    z-index:1;

    -webit-transform:translateX(-50%);

    -moz-transform:translateX(-50%);

    transform:translateX(-50%);

}

</style>

‘use strict’;

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) {

throw new TypeError(“Cannot call a class as a function”); } }

var canvas = document.getElementsByTagName(‘canvas’)[0];

canvas.width = canvas.clientWidth;

canvas.height = canvas.clientHeight;

var params = { alpha: false, depth: false, stencil: false, antialias: false };

var gl = canvas.getContext(‘webgl2’, params);

var isWebGL2 = !!gl;

if (!isWebGL2) {

    gl = canvas.getContext(‘webgl’, params) || canvas.getContext(‘experimental-webgl’, params);

}

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

var halfFloat = gl.getExtension(‘OES_texture_half_float’);

var 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’);

}

var TEXTURE_DOWNSAMPLE = 0.5;

var DENSITY_DISSIPATION = 0.98;

var VELOCITY_DISSIPATION = 0.99;

var SPLAT_RADIUS = 0.005;

var CURL = 30;

var PRESSURE_ITERATIONS = 10;

var GLProgram = function () {

    function GLProgram(vertexShader, fragmentShader) {

        _classCallCheck(this, GLProgram);

        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);

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

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

            var 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) {

    var shader = gl.createShader(type);

    gl.shaderSource(shader, source);

    gl.compileShader(shader);

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

    return shader;

};

var baseVertexShader = compileShader(gl.VERTEX_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    attribute vec2 aPosition;\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform vec2 texelSize;\n\n    void main () {\n        vUv = aPosition * 0.5 + 0.5;\n        vL = vUv – vec2(texelSize.x, 0.0);\n        vR = vUv + vec2(texelSize.x, 0.0);\n        vT = vUv + vec2(0.0, texelSize.y);\n        vB = vUv – vec2(0.0, texelSize.y);\n        gl_Position = vec4(aPosition, 0.0, 1.0);\n    }\n‘);

var displayShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uTexture;\n\n    void main () {\n        gl_FragColor = texture2D(uTexture, vUv);\n    }\n‘);

var splatShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uTarget;\n    uniform float aspectRatio;\n    uniform vec3 color;\n    uniform vec2 point;\n    uniform float radius;\n\n    void main () {\n        vec2 p = vUv – point.xy;\n        p.x *= aspectRatio;\n        vec3 splat = exp(-dot(p, p) / radius) * color;\n        vec3 base = texture2D(uTarget, vUv).xyz;\n        gl_FragColor = vec4(base + splat, 1.0);\n    }\n‘);

var advectionManualFilteringShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uVelocity;\n    uniform sampler2D uSource;\n    uniform vec2 texelSize;\n    uniform float dt;\n    uniform float dissipation;\n\n    vec4 bilerp (in sampler2D sam, in vec2 p) {\n        vec4 st;\n        st.xy = floor(p – 0.5) + 0.5;\n        st.zw = st.xy + 1.0;\n        vec4 uv = st * texelSize.xyxy;\n        vec4 a = texture2D(sam, uv.xy);\n        vec4 b = texture2D(sam, uv.zy);\n        vec4 c = texture2D(sam, uv.xw);\n        vec4 d = texture2D(sam, uv.zw);\n        vec2 f = p – st.xy;\n        return mix(mix(a, b, f.x), mix(c, d, f.x), f.y);\n    }\n\n    void main () {\n        vec2 coord = gl_FragCoord.xy – dt * texture2D(uVelocity, vUv).xy;\n        gl_FragColor = dissipation * bilerp(uSource, coord);\n        gl_FragColor.a = 1.0;\n    }\n‘);

var advectionShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    uniform sampler2D uVelocity;\n    uniform sampler2D uSource;\n    uniform vec2 texelSize;\n    uniform float dt;\n    uniform float dissipation;\n\n    void main () {\n        vec2 coord = vUv – dt * texture2D(uVelocity, vUv).xy * texelSize;\n        gl_FragColor = dissipation * texture2D(uSource, coord);\n    }\n‘);

var divergenceShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uVelocity;\n\n    vec2 sampleVelocity (in vec2 uv) {\n        vec2 multiplier = vec2(1.0, 1.0);\n        if (uv.x < 0.0) { uv.x = 0.0; multiplier.x = -1.0; }\n        if (uv.x > 1.0) { uv.x = 1.0; multiplier.x = -1.0; }\n        if (uv.y < 0.0) { uv.y = 0.0; multiplier.y = -1.0; }\n        if (uv.y > 1.0) { uv.y = 1.0; multiplier.y = -1.0; }\n        return multiplier * texture2D(uVelocity, uv).xy;\n    }\n\n    void main () {\n        float L = sampleVelocity(vL).x;\n        float R = sampleVelocity(vR).x;\n        float T = sampleVelocity(vT).y;\n        float B = sampleVelocity(vB).y;\n        float div = 0.5 * (R – L + T – B);\n        gl_FragColor = vec4(div, 0.0, 0.0, 1.0);\n    }\n‘);

var curlShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uVelocity;\n\n    void main () {\n        float L = texture2D(uVelocity, vL).y;\n        float R = texture2D(uVelocity, vR).y;\n        float T = texture2D(uVelocity, vT).x;\n        float B = texture2D(uVelocity, vB).x;\n        float vorticity = R – L – T + B;\n        gl_FragColor = vec4(vorticity, 0.0, 0.0, 1.0);\n    }\n‘);

var vorticityShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uVelocity;\n    uniform sampler2D uCurl;\n    uniform float curl;\n    uniform float dt;\n\n    void main () {\n        float L = texture2D(uCurl, vL).y;\n        float R = texture2D(uCurl, vR).y;\n        float T = texture2D(uCurl, vT).x;\n        float B = texture2D(uCurl, vB).x;\n        float C = texture2D(uCurl, vUv).x;\n        vec2 force = vec2(abs(T) – abs(B), abs(R) – abs(L));\n        force *= 1.0 / length(force + 0.00001) * curl * C;\n        vec2 vel = texture2D(uVelocity, vUv).xy;\n        gl_FragColor = vec4(vel + force * dt, 0.0, 1.0);\n    }\n‘);

var pressureShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uPressure;\n    uniform sampler2D uDivergence;\n\n    vec2 boundary (in vec2 uv) {\n        uv = min(max(uv, 0.0), 1.0);\n        return uv;\n    }\n\n    void main () {\n        float L = texture2D(uPressure, boundary(vL)).x;\n        float R = texture2D(uPressure, boundary(vR)).x;\n        float T = texture2D(uPressure, boundary(vT)).x;\n        float B = texture2D(uPressure, boundary(vB)).x;\n        float C = texture2D(uPressure, vUv).x;\n        float divergence = texture2D(uDivergence, vUv).x;\n        float pressure = (L + R + B + T – divergence) * 0.25;\n        gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);\n    }\n‘);

var gradientSubtractShader = compileShader(gl.FRAGMENT_SHADER, ‘\n    precision highp float;\n    precision mediump sampler2D;\n\n    varying vec2 vUv;\n    varying vec2 vL;\n    varying vec2 vR;\n    varying vec2 vT;\n    varying vec2 vB;\n    uniform sampler2D uPressure;\n    uniform sampler2D uVelocity;\n\n    vec2 boundary (in vec2 uv) {\n        uv = min(max(uv, 0.0), 1.0);\n        return uv;\n    }\n\n    void main () {\n        float L = texture2D(uPressure, boundary(vL)).x;\n        float R = texture2D(uPressure, boundary(vR)).x;\n        float T = texture2D(uPressure, boundary(vT)).x;\n        float B = texture2D(uPressure, boundary(vB)).x;\n        vec2 velocity = texture2D(uVelocity, vUv).xy;\n        velocity.xy -= vec2(R – L, T – B);\n        gl_FragColor = vec4(velocity, 0.0, 1.0);\n    }\n‘);

var 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);

    };

}();

function clear(target) {

    gl.bindFramebuffer(gl.FRAMEBUFFER, target);

    gl.clear(gl.COLOR_BUFFER_BIT);

}

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

    gl.activeTexture(gl.TEXTURE0 + texId);

    var 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);

    var 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) {

    var fbo1 = createFBO(texId, w, h, internalFormat, format, type, param);

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

    return {

        get first() {

            return fbo1;

        },

        get second() {

            return fbo2;

        },

        swap: function swap() {

            var temp = fbo1;

            fbo1 = fbo2;

            fbo2 = temp;

        }

    };

}

var textureWidth = undefined;

var textureHeight = undefined;

var density = undefined;

var velocity = undefined;

var divergence = undefined;

var curl = undefined;

var pressure = undefined;

function initFramebuffers() {

    textureWidth = gl.drawingBufferWidth >> TEXTURE_DOWNSAMPLE;

    textureHeight = gl.drawingBufferHeight >> TEXTURE_DOWNSAMPLE;

    var internalFormat = isWebGL2 ? gl.RGBA16F : gl.RGBA;

    var internalFormatRG = isWebGL2 ? gl.RG16F : gl.RGBA;

    var formatRG = isWebGL2 ? gl.RG : gl.RGBA;

    var texType = isWebGL2 ? gl.HALF_FLOAT : halfFloat.HALF_FLOAT_OES;

    density = createDoubleFBO(0, textureWidth, textureHeight, internalFormat, gl.RGBA, texType, support_linear_float ? gl.LINEAR : gl.NEAREST);

    velocity = createDoubleFBO(2, textureWidth, textureHeight, internalFormatRG, formatRG, texType, support_linear_float ? gl.LINEAR : gl.NEAREST);

    divergence = createFBO(4, textureWidth, textureHeight, internalFormatRG, formatRG, texType, gl.NEAREST);

    curl = createFBO(5, textureWidth, textureHeight, internalFormatRG, formatRG, texType, gl.NEAREST);

    pressure = createDoubleFBO(6, textureWidth, textureHeight, internalFormatRG, formatRG, texType, gl.NEAREST);

} 

initFramebuffers();

var displayProgram = new GLProgram(baseVertexShader, displayShader);

var splatProgram = new GLProgram(baseVertexShader, splatShader);

var advectionProgram = new GLProgram(baseVertexShader, support_linear_float ? advectionShader : advectionManualFilteringShader);

var divergenceProgram = new GLProgram(baseVertexShader, divergenceShader);

var curlProgram = new GLProgram(baseVertexShader, curlShader);

var vorticityProgram = new GLProgram(baseVertexShader, vorticityShader);

var pressureProgram = new GLProgram(baseVertexShader, pressureShader);

var gradienSubtractProgram = new GLProgram(baseVertexShader, gradientSubtractShader);

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, 100];

}

var pointers = [];

pointers.push(new pointerPrototype());

for (var i = 0; i < 10; i++) {

    var color = [Math.random() * 10, Math.random() * 10, Math.random() * 10];

    var x = canvas.width * Math.random();

    var y = canvas.height * Math.random();

    var dx = 100 * (Math.random() – 0.5);

    var dy = 100 * (Math.random() – 0.5);

    splat(x, y, dx, dy, color);

}

var lastTime = Date.now();

Update();

function Update() {

    resizeCanvas();

    var dt = Math.min((Date.now() – lastTime) / 100, 0.016);

    lastTime = Date.now();

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

    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, 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, DENSITY_DISSIPATION);

    blit(density.second[1]);

    density.swap();

    for (var i = 0; i < pointers.length; i++) {

        var 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, 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]);

    clear(pressure.first[1]);

    pressureProgram.bind();

    gl.uniform2f(pressureProgram.uniforms.texelSize, 1.0 / textureWidth, 1.0 / textureHeight);

    gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence[2]);

    for (var i = 0; i < PRESSURE_ITERATIONS; i++) {

        gl.uniform1i(pressureProgram.uniforms.uPressure, pressure.first[2]);

        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, 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() {

    if (canvas.width != canvas.clientWidth || canvas.height != canvas.clientHeight) {

        canvas.width = canvas.clientWidth;

        canvas.height = canvas.clientHeight;

        initFramebuffers();

    }

} 

canvas.addEventListener(‘mousemove’, function (e) {

    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;

    pointers[0].down = true;

}); 

canvas.addEventListener(‘touchmove’, function (e) {

    e.preventDefault();

    var touches = e.targetTouches;

    for (var i = 0; i < e.touches.length; i++) {

        var 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);

canvas.addEventListener(‘mousedown’, function () {

    pointers[0].down = true;

    pointers[0].color = [Math.random() + 0.2, Math.random() + 0.2, Math.random() + 0.2];

});

canvas.addEventListener(‘touchstart’, function (e) {

    var touches = e.targetTouches;

    for (var i = 0; i < touches.length; 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 = [Math.random() + 0.2, Math.random() + 0.2, Math.random() + 0.2];

    }

});

window.addEventListener(‘mouseup’, function () {

    pointers[0].down = true;

});

window.addEventListener(‘touchend’, function (e) {

    var touches = e.changedTouches;

    for (var i = 0; i < touches.length; i++) {

        for (var j = 0; j < pointers.length; j++) {

            if (touches[i].identifier == pointers[j].id) pointers[j].down = false;

        }

    }

});

</script>