three.js/examples/js/shaders/KaleidoShader.js

( function () {

	/**
 * Kaleidoscope Shader
 * Radial reflection around center point
 * Ported from: http://pixelshaders.com/editor/
 * by Toby Schachman / http://tobyschachman.com/
 *
 * sides: number of reflections
 * angle: initial angle in radians
 */
	var KaleidoShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'sides': {
				value: 6.0
			},
			'angle': {
				value: 0.0
			}
		},
		vertexShader: [ 'varying vec2 vUv;', 'void main() {', '	vUv = uv;', '	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}' ].join( '\n' ),
		fragmentShader: [ 'uniform sampler2D tDiffuse;', 'uniform float sides;', 'uniform float angle;', 'varying vec2 vUv;', 'void main() {', '	vec2 p = vUv - 0.5;', '	float r = length(p);', '	float a = atan(p.y, p.x) + angle;', '	float tau = 2. * 3.1416 ;', '	a = mod(a, tau/sides);', '	a = abs(a - tau/sides/2.) ;', '	p = r * vec2(cos(a), sin(a));', '	vec4 color = texture2D(tDiffuse, p + 0.5);', '	gl_FragColor = color;', '}' ].join( '\n' )
	};

	THREE.KaleidoShader = KaleidoShader;

} )();