A Three.js shader showing digital static noise

static-noise-three-shader.js

(function (THREE)
{
    /**
     * @author Felix Turner / www.airtight.cc / @felixturner
     *
     * Static effect. Additively blended digital noise.
     *
     * amount - amount of noise to add (0 - 1)
     * size - size of noise grains (pixels)
     *
     * The MIT License
     *
     * Copyright (c) 2014 Felix Turner
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy
     * of this software and associated documentation files (the "Software"), to deal
     * in the Software without restriction, including without limitation the rights
     * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     * copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in
     * all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
     * THE SOFTWARE.
     */
    THREE.StaticNoiseShader = {

        uniforms: {

            "tDiffuse": { type: "t", value: null },
            "time":     { type: "f", value: 0.0 },
            "amount":   { type: "f", value: 0.5 },
            "size":     { type: "f", value: 4.0 }
        },

        vertexShader: [

            "varying vec2 vUv;",

            "void main() {",

                "vUv = uv;",
                "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );",

            "}"

        ].join("\n"),

        fragmentShader: [

            "uniform sampler2D tDiffuse;",
            "uniform float time;",
            "uniform float amount;",
            "uniform float size;",

            "varying vec2 vUv;",

            "float rand(vec2 co) {",
                "return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);",
            "}",

            "void main() {",
                "vec2 p = vUv;",
                "vec4 color = texture2D(tDiffuse, p);",
                "float xs = floor(gl_FragCoord.x / size);",
                "float ys = floor(gl_FragCoord.y / size);",
                "vec4 snow = vec4(rand(vec2(xs * time,ys * time))*amount);",
                "gl_FragColor = color + snow;", //additive
            "}"

        ].join("\n")
    };
})(THREE);