/**
 * @module KaleidoShader
 * @three_import import { KaleidoShader } from 'three/addons/shaders/KaleidoShader.js';
 */

/**
 * Kaleidoscope Shader.
 * Radial reflection around center point
 * Ported from: {@link http://pixelshaders.com/editor/}
 * by [Toby Schachman]{@link http://tobyschachman.com/}
 *
 * sides: number of reflections
 * angle: initial angle in radians
 *
 * @constant
 * @type {ShaderMaterial~Shader}
 */
const KaleidoShader = {

	name: '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;

		}`

};

export { KaleidoShader };
