I am currently developing a very primitive form of gradient “noise” in a vertex shader. Tecknically it might be wrong to even call it noise, but it has a rather similar effect. I will post (relevant parts of) the code to simplify explaining:

```
#define TABSIZE 16
#define TABMASK TABSIZE - 1
// const?
int permtable[TABSIZE] = {
5, 9, 2, 7, 10, 8, 11, 3, 15, 6, 13, 12, 1, 4, 14, 0
};
// const?
vec3 vdir[TABSIZE] = {
vec3(-0.3429, 0.8639, -0.3689), vec3(0.3442, 0.1373, -0.9288),...
};
int perm(float x)
{
int i = int(abs(mod(x, float(TABMASK))));
return permtable[i];
}
int index(vec3 vec)
{
int tmp = perm(vec[2]);
tmp = tmp + int(vec[1]);
tmp = perm(tmp);
tmp = tmp + int(vec[0]);
tmp = perm(tmp);
return tmp;
}
vec3 glattice(vec3 vec)
{
int i = index(vec);
return vdir[i];
}
vec4 hnoise(float ax, float ay, float az, float at)
{
// Integer parts of input vector
vec3 invec = vec3(ax, ay, az);
vec3 ipart = abs(floor(invec));
// THIS CALL TO GLATTICE DOESN'T WORK!
// GIVES LINKER ERROR
vec3 tmp2 = glattice(float(ipart));
// THIS CALL TO GLATTICE DOES WORK!
vec3 tmp66 = glattice(vec3(0.0, 1.0, -2.0));
// result = [x,y,z,r], r = radius
// DOESN'T DO ANYTHING AT THE MOMENT
// SINCE THE OTHER STUFF DOESN'T WORK!
vec4 result;
result.x = 1.0;
result.y = 0.0;
result.z = 0.0;
result.w = at;
return result;
}
```

It is all very confusing. The conclusion I have come to is that I can’t really do anything with the input to hnoise… At the moment the function doesn’t do much. It has been stripped to show the problem more clearly.

/Tommy