Original Post
In this thread I'm going to speak of some experiments I've been making on 3D noise generated on the GPU. Reference test The reference 3D noise implementation is from Stefan Gustavson in GLSL. Here is the thread about it with a link to the full GLSL code: GLSL 3D Noise by Stefan Gustavson I'm generating, combining and rendering 32 octaves of his noise per pixel into a 513x513 fp32 texture. I'm getting 20 fps on an ATI Radeon X1950 XT. Computed noise The idea with the computed noise basis is to generate some kind of coherent noise (like Perlin noise), but avoiding the permutation/lookup tables and integer/bit-shifting arithmetics. Originally, it was developped for the CPU, to be easily optimized in SSE2. Here's the port to GLSL:
float randomizer(const float x)
{
float z = mod(x, 5612.0);
z = mod(z, 3.1415927 * 2.0);
return(fract(cos(z) * 56812.5453));
}
const float A = 1.0;
const float B = 57.0;
const float C = 113.0;
const vec3 ABC = vec3(A, B, C);
float cnoise(const in vec3 xx)
{
vec3 x = mod(xx + 32768.0, 65536.0);
vec3 ix = floor(x);
vec3 fx = fract(x);
vec3 wx = fx*fx*(3.0-2.0*fx);
float nn = dot(ix, ABC);
float re = mix(mix(mix(randomizer(nn),
randomizer(nn + A),wx.x),
mix(randomizer(nn + B),
randomizer(nn + A + B),wx.x),wx.y),
mix(mix(randomizer(nn + C),
randomizer(nn + C + A),wx.x),
mix(randomizer(nn + C + B),
randomizer(nn + C + B + A),wx.x),wx.y),wx.z);
return 1.0 - 2.0 * re;
}
vec4 randomizer4(const vec4 x)
{
vec4 z = mod(x, vec4(5612.0));
z = mod(z, vec4(3.1415927 * 2.0));
return(fract(cos(z) * vec4(56812.5453)));
}
const float A = 1.0;
const float B = 57.0;
const float C = 113.0;
const vec3 ABC = vec3(A, B, C);
const vec4 A3 = vec4(0, B, C, C+B);
const vec4 A4 = vec4(A, A+B, C+A, C+A+B);
float cnoise4(const in vec3 xx)
{
vec3 x = mod(xx + 32768.0, 65536.0);
vec3 ix = floor(x);
vec3 fx = fract(x);
vec3 wx = fx*fx*(3.0-2.0*fx);
float nn = dot(ix, ABC);
vec4 N1 = nn + A3;
vec4 N2 = nn + A4;
vec4 R1 = randomizerSin4(N1);
vec4 R2 = randomizerSin4(N2);
vec4 R = mix(R1, R2, wx.x);
float re = mix(mix(R.x, R.y, wx.y), mix(R.z, R.w, wx.y), wx.z);
return 1.0 - 2.0 * re;
}
