23 lines
574 B
HLSL
23 lines
574 B
HLSL
/*
|
|
contributors: [Stefan Gustavson, Ian McEwan]
|
|
description: grad4, used for snoise(float4 v)
|
|
use: <float4> grad4(<float> j, <float4> ip)
|
|
*/
|
|
|
|
#ifndef FNC_GRAD4
|
|
#define FNC_GRAD4
|
|
|
|
float4 grad4(float j, float4 ip) {
|
|
const float4 ones = float4(1.0, 1.0, 1.0, -1.0);
|
|
float4 p, s;
|
|
|
|
p.xyz = floor( frac (float3(j, j, j) * ip.xyz) * 7.0) * ip.z - 1.0;
|
|
p.w = 1.5 - dot(abs(p.xyz), ones.xyz);
|
|
// GLSL: s = float4(lessThan(p, float4(0.0)));
|
|
s = float4(1 - step(float4(0, 0, 0, 0), p));
|
|
p.xyz = p.xyz + (s.xyz * 2.0 - 1.0) * s.www;
|
|
|
|
return p;
|
|
}
|
|
|
|
#endif
|