float taylorInvSqrt(float r)
{
return ( 0.83666002653408 + 0.7*0.85373472095314 - 0.85373472095314 * r );
}
float permute(float x0,vec3 p) {
float x1 = mod(x0 * p.y, p.x);
return floor( mod( (x1 + p.z) *x0, p.x ));
}
vec2 permute(vec2 x0,vec3 p) {
vec2 x1 = mod(x0 * p.y, p.x);
return floor( mod( (x1 + p.z) *x0, p.x ));
}
vec3 permute(vec3 x0,vec3 p) {
vec3 x1 = mod(x0 * p.y, p.x);
return floor( mod( (x1 + p.z) *x0, p.x ));
}
vec4 permute(vec4 x0,vec3 p) {
vec4 x1 = mod(x0 * p.y, p.x);
return floor( mod( (x1 + p.z) *x0, p.x ));
}
float simplexNoise2(vec2 v)
{
const vec2 C = vec2(0.211324865405187134, // (3.0-sqrt(3.0))/6.;
0.366025403784438597); // 0.5*(sqrt(3.0)-1.);
const vec3 D = vec3( 0., 0.5, 2.0) * 3.14159265358979312;
// First corner
vec2 i = floor(v + dot(v, C.yy) );
vec2 x0 = v - i + dot(i, C.xx);
// Other corners
vec2 i1 = (x0.x > x0.y) ? vec2(1.,0.) : vec2(0.,1.) ;
// x0 = x0 - 0. + 0. * C
vec2 x1 = x0 - i1 + 1. * C.xx ;
vec2 x2 = x0 - 1. + 2. * C.xx ;
// Permutations
i = mod(i, pParam.x);
vec3 p = permute( permute(
i.y + vec3(0., i1.y, 1. ), pParam.xyz)
+ i.x + vec3(0., i1.x, 1. ), pParam.xyz);
// ( N points uniformly over a line, mapped onto a diamond.)
vec3 x = fract(p / pParam.w) ;
vec3 h = 0.5 - abs(x) ;
vec3 sx = vec3(lessThan(x,D.xxx)) *2. -1.;
vec3 sh = vec3(lessThan(h,D.xxx));
vec3 a0 = x + sx*sh;
vec2 p0 = vec2(a0.x,h.x);
vec2 p1 = vec2(a0.y,h.y);
vec2 p2 = vec2(a0.z,h.z);
#ifdef NORMALISE_GRADIENTS
p0 *= taylorInvSqrt(dot(p0,p0));
p1 *= taylorInvSqrt(dot(p1,p1));
p2 *= taylorInvSqrt(dot(p2,p2));
#endif
vec3 g = 2.0 * vec3( dot(p0, x0), dot(p1, x1), dot(p2, x2) );
// mix
vec3 m = max(0.5 - vec3(dot(x0,x0), dot(x1,x1), dot(x2,x2)), 0.);
m = m*m ;
return 1.66666* 70.*dot(m*m, g);
}
Originally Posted by kRogue
