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

/**
 * 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' )

};

export { KaleidoShader };