dfhack/library/include/modules/PerlinNoise.inc

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#pragma once
namespace DFHack {
namespace Random {
/*
* A good explanation:
* http://webstaff.itn.liu.se/~stegu/TNM022-2005/perlinnoiselinks/perlin-noise-math-faq.html
*/
// Interpolation functions
template<class T>
inline T s_curve(T t)
{
// Classical function
//return t * t * (3 - 2*t);
// 2002 version from http://mrl.nyu.edu/~perlin/paper445.pdf
return t * t * t * (t * (t * 6 - 15) + 10);
}
template<class T>
inline T lerp(T s, T a, T b)
{
return a + s * (b-a);
}
// Dot product of VSIZE vectors pointed by pa, pb
template<class T, unsigned i>
struct DotProduct {
static inline T eval(T *pa, T *pb);
};
template<class T>
struct DotProduct<T,0> {
static inline T eval(T *pa, T *pb) { return pa[0]*pb[0]; }
};
template<class T, unsigned i>
inline T DotProduct<T,i>::eval(T *pa, T *pb) {
return DotProduct<T,i-1>::eval(pa, pb) + pa[i]*pb[i];
}
// Templates used to force unrolling and inlining of the loops
template<class T, unsigned VSIZE, unsigned BITS, class IDXT>
template<unsigned mask>
struct PerlinNoise<T,VSIZE,BITS,IDXT>::Impl<mask,-1> {
typedef typename PerlinNoise<T,VSIZE,BITS,IDXT>::Temp Temp;
static inline void setup(PerlinNoise<T,VSIZE,BITS,IDXT> *, const T *, Temp *) {}
static inline T eval(PerlinNoise<T,VSIZE,BITS,IDXT> *self, Temp *pt, unsigned idx, T *pq);
};
// Initialization of the temporaries from input coordinates
template<class T, unsigned VSIZE, unsigned BITS, class IDXT>
template<unsigned mask, int i>
inline void PerlinNoise<T,VSIZE,BITS,IDXT>::Impl<mask,i>::setup(
PerlinNoise<T,VSIZE,BITS,IDXT> *self, const T *pv, Temp *pt
) {
Impl<mask,i-1>::setup(self, pv, pt);
T t = std::floor(pv[i]);
pt[i].s = s_curve(pt[i].r0 = pv[i] - t);
unsigned b = unsigned(int32_t(t));
pt[i].b0 = self->idxmap[i][b & mask];
pt[i].b1 = self->idxmap[i][(b+1) & mask];
}
// Main recursion. Uses tables from self and pt.
// Recursion changes current index idx, and current offset vector pq.
template<class T, unsigned VSIZE, unsigned BITS, class IDXT>
template<unsigned mask>
inline T PerlinNoise<T,VSIZE,BITS,IDXT>::Impl<mask, -1>::eval(
PerlinNoise<T,VSIZE,BITS,IDXT> *self, Temp *pt, unsigned idx, T *pq
) {
return DotProduct<T,VSIZE-1>::eval(pq, self->gradients[idx]);
}
template<class T, unsigned VSIZE, unsigned BITS, class IDXT>
template<unsigned mask, int i>
inline T PerlinNoise<T,VSIZE,BITS,IDXT>::Impl<mask,i>::eval(
PerlinNoise<T,VSIZE,BITS,IDXT> *self, Temp *pt, unsigned idx, T *pq
) {
pq[i] = pt[i].r0;
T u = Impl<mask,i-1>::eval(self, pt, idx ^ pt[i].b0, pq);
pq[i] -= 1;
T v = Impl<mask,i-1>::eval(self, pt, idx ^ pt[i].b1, pq);
return lerp(pt[i].s, u, v);
}
// Actual methods of the object
template<class T, unsigned VSIZE, unsigned BITS, class IDXT>
void PerlinNoise<T,VSIZE,BITS,IDXT>::init(MersenneRNG &rng)
{
STATIC_ASSERT(VSIZE > 0 && BITS <= 8*sizeof(IDXT));
// Random unit gradient vectors
for (unsigned i = 0; i < TSIZE; i++)
rng.unitvector(gradients[i], VSIZE);
// Random permutation tables
for (unsigned j = 0; j < VSIZE; j++)
{
for (unsigned i = 0; i < TSIZE; i++)
idxmap[j][i] = i;
rng.permute(idxmap[j], TSIZE);
}
}
template<class T, unsigned VSIZE, unsigned BITS, class IDXT>
T PerlinNoise<T,VSIZE,BITS,IDXT>::eval(const T coords[VSIZE])
{
// Precomputed properties from the coordinates
Temp tmp[VSIZE];
// Temporary used to build the current offset vector
T q[VSIZE];
Impl<TSIZE-1,VSIZE-1>::setup(this, coords, tmp);
return Impl<TSIZE-1,VSIZE-1>::eval(this, tmp, 0, q);
}
}} // namespace