// GLSL textureless classic 2D noise "cnoise",
// with an RSL-style periodic variant "pnoise".
// Author:  Stefan Gustavson (stefan.gustavson@liu.se)
// Version: 2011-08-22
//
// Many thanks to Ian McEwan of Ashima Arts for the
// ideas for permutation and gradient selection.
//
// Copyright (c) 2011 Stefan Gustavson. All rights reserved.
// Distributed under the MIT license. See LICENSE file.
// https://github.com/ashima/webgl-noise
//

// poor man's hlsl -> glsl conversion
#define vec2 fixed2
#define vec3 fixed3
#define vec4 fixed4
#define fract frac
#define mix lerp

vec4 mod289(vec4 x)
{
	return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 permute(vec4 x)
{
	return mod289(((x*34.0)+1.0)*x);
}

vec4 taylorInvSqrt(vec4 r)
{
	return 1.79284291400159 - 0.85373472095314 * r;
}

vec2 fade(vec2 t) 
{
	return t*t*t*(t*(t*6.0-15.0)+10.0);
}

// Classic Perlin noise
float cnoise(vec2 P)
{
	vec4 Pi = floor(P.xyxy) + vec4(0.0, 0.0, 1.0, 1.0);
	vec4 Pf = fract(P.xyxy) - vec4(0.0, 0.0, 1.0, 1.0);
	Pi = mod289(Pi); // To avoid truncation effects in permutation
	vec4 ix = Pi.xzxz;
	vec4 iy = Pi.yyww;
	vec4 fx = Pf.xzxz;
	vec4 fy = Pf.yyww;

	vec4 i = permute(permute(ix) + iy);

	vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0 ;
	vec4 gy = abs(gx) - 0.5 ;
	vec4 tx = floor(gx + 0.5);
	gx = gx - tx;

	vec2 g00 = vec2(gx.x,gy.x);
	vec2 g10 = vec2(gx.y,gy.y);
	vec2 g01 = vec2(gx.z,gy.z);
	vec2 g11 = vec2(gx.w,gy.w);

	vec4 norm = taylorInvSqrt(vec4(dot(g00, g00), dot(g01, g01), dot(g10, g10), dot(g11, g11)));
	g00 *= norm.x;  
	g01 *= norm.y;  
	g10 *= norm.z;  
	g11 *= norm.w;  

	float n00 = dot(g00, vec2(fx.x, fy.x));
	float n10 = dot(g10, vec2(fx.y, fy.y));
	float n01 = dot(g01, vec2(fx.z, fy.z));
	float n11 = dot(g11, vec2(fx.w, fy.w));

	vec2 fade_xy = fade(Pf.xy);
	vec2 n_x = mix(vec2(n00, n01), vec2(n10, n11), fade_xy.x);
	float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
	return 2.3 * n_xy;
}

// Classic Perlin noise, periodic variant
float pnoise(vec2 P, vec2 rep)
{
	vec4 Pi = floor(P.xyxy) + vec4(0.0, 0.0, 1.0, 1.0);
	vec4 Pf = fract(P.xyxy) - vec4(0.0, 0.0, 1.0, 1.0);
	Pi = fmod(Pi, rep.xyxy); // To create noise with explicit period
	Pi = mod289(Pi);        // To avoid truncation effects in permutation
	vec4 ix = Pi.xzxz;
	vec4 iy = Pi.yyww;
	vec4 fx = Pf.xzxz;
	vec4 fy = Pf.yyww;

	vec4 i = permute(permute(ix) + iy);

	vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0 ;
	vec4 gy = abs(gx) - 0.5 ;
	vec4 tx = floor(gx + 0.5);
	gx = gx - tx;

	vec2 g00 = vec2(gx.x,gy.x);
	vec2 g10 = vec2(gx.y,gy.y);
	vec2 g01 = vec2(gx.z,gy.z);
	vec2 g11 = vec2(gx.w,gy.w);

	vec4 norm = taylorInvSqrt(vec4(dot(g00, g00), dot(g01, g01), dot(g10, g10), dot(g11, g11)));
	g00 *= norm.x;  
	g01 *= norm.y;  
	g10 *= norm.z;  
	g11 *= norm.w;  

	float n00 = dot(g00, vec2(fx.x, fy.x));
	float n10 = dot(g10, vec2(fx.y, fy.y));
	float n01 = dot(g01, vec2(fx.z, fy.z));
	float n11 = dot(g11, vec2(fx.w, fy.w));

	vec2 fade_xy = fade(Pf.xy);
	vec2 n_x = mix(vec2(n00, n01), vec2(n10, n11), fade_xy.x);
	float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
	return 2.3 * n_xy;
}

