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
 */

	const KaleidoShader = {
		uniforms: {
			'tDiffuse': {
				value: null
			},
			'sides': {
				value: 6.0
			},
			'angle': {
				value: 0.0
			}
		},
		vertexShader: /* glsl */`

		varying vec2 vUv;

		void main() {

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

		}`,
		fragmentShader: /* glsl */`

		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;

		}`
	};

	THREE.KaleidoShader = KaleidoShader;

} )();