//

// 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

//

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 snoise(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

// First corner

vec2 i = floor(v + dot(v, C.yy) );

vec2 x0 = v - i + dot(i, C.xx);

// Other corners

vec2 i1;

//i1.x = step( x0.y, x0.x ); // x0.x > x0.y ? 1.0 : 0.0

//i1.y = 1.0 - i1.x;

i1 = (x0.x > x0.y) ? vec2(1.0, 0.0) : vec2(0.0, 1.0);

// x0 = x0 - 0.0 + 0.0 * C.xx ;

// x1 = x0 - i1 + 1.0 * C.xx ;

// x2 = x0 - 1.0 + 2.0 * C.xx ;

vec4 x12 = x0.xyxy + C.xxzz;

x12.xy -= i1;

// Permutations

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 ;

// Gradients: 41 points uniformly over a line, mapped onto a diamond.

// The ring size 17*17 = 289 is close to a multiple of 41 (41*7 = 287)

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;

// Normalise gradients implicitly by scaling m

// Approximation of: m *= inversesqrt( a0*a0 + h*h );

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

// Compute final noise value at P

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);

}