Frag Random

Code

precision mediump float;
#define GLSLIFY 1
// Common uniforms
uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;
uniform float u_frame;

/*
 * Random number generator with a vec2 seed
 *
 * Credits:
 * http://byteblacksmith.com/improvements-to-the-canonical-one-liner-glsl-rand-for-opengl-es-2-0
 * https://github.com/mattdesl/glsl-random
 */
highp float random2d(vec2 co) {
    highp float a = 12.9898;
    highp float b = 78.233;
    highp float c = 43758.5453;
    highp float dt = dot(co.xy, vec2(a, b));
    highp float sn = mod(dt, 3.14);
    return fract(sin(sn) * c);
}

/*
 * The main program
 */
void main() {
    // Create a grid of squares that depends on the mouse position
    vec2 square = floor((gl_FragCoord.xy - u_mouse) / 30.0);

    // Give a random color to each square
    vec3 square_color = vec3(random2d(square), random2d(1.234 * square), 1.0);

    // Fragment shader output
    gl_FragColor = vec4(square_color, 1.0);
}