kampos/src/noise/simplex-2d.js

Tiny and fast effects compositor on WebGL

/*!
* Description : Array and textureless GLSL 2D simplex noise function.
*      Author : Ian McEwan, Ashima Arts.
*  Maintainer : stegu
*     Lastmod : 20110822 (ijm)
*     License : Copyright (C) 2011 Ashima Arts. All rights reserved.
*               Distributed under the MIT License. See LICENSE file.
*               https://github.com/ashima/webgl-noise
*               https://github.com/stegu/webgl-noise
*/
/**
 * Implementation of a 2D Simplex noise. Exposes a `noise(vec2 v)` function for use inside fragment shaders.
 */
export default `
vec3 mod289(vec3 x) {
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec2 mod289(vec2 x) {
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec3 permute(vec3 x) {
    return mod289(((x*34.0)+10.0)*x);
}

float noise (vec2 v) {
    const vec4 C = vec4(0.211324865405187,  // (3.0-sqrt(3.0))/6.0
    0.366025403784439,  // 0.5*(sqrt(3.0)-1.0)
    -0.577350269189626,  // -1.0 + 2.0 * C.x
    0.024390243902439); // 1.0 / 41.0
    vec2 i = floor(v + dot(v, C.yy));
    vec2 x0 = v - i + dot(i, C.xx);

    vec2 i1;
    i1 = (x0.x > x0.y) ? vec2(1.0, 0.0) : vec2(0.0, 1.0);
    vec4 x12 = x0.xyxy + C.xxzz;
    x12.xy -= i1;

    i = mod289(i); // Avoid truncation effects in permutation
    vec3 p = permute(permute( i.y + vec3(0.0, i1.y, 1.0 ))
    + i.x + vec3(0.0, i1.x, 1.0));

    vec3 m = max(0.5 - vec3(dot(x0,x0), dot(x12.xy,x12.xy), dot(x12.zw,x12.zw)), 0.0);
    m = m*m ;
    m = m*m ;

    vec3 x = 2.0 * fract(p * C.www) - 1.0;
    vec3 h = abs(x) - 0.5;
    vec3 ox = floor(x + 0.5);
    vec3 a0 = x - ox;

    m *= 1.79284291400159 - 0.85373472095314 * ( a0*a0 + h*h );

    vec3 g;
    g.x  = a0.x * x0.x + h.x * x0.y;
    g.yz = a0.yz * x12.xz + h.yz * x12.yw;
    return 130.0 * dot(m, g);
}`;