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tweak hash function (sdf)

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This commit is contained in:
Erwin Coumans
2019-11-18 21:46:05 -08:00
parent d26752b232
commit 363dc8d431
1 changed files with 39 additions and 25 deletions
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64
src/BulletSoftBody/btSparseSDF.h
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@@ -20,27 +20,38 @@ subject to the following restrictions:
#include "BulletCollision/CollisionDispatch/btCollisionObject.h"
#include "BulletCollision/NarrowPhaseCollision/btGjkEpa2.h"
// Modified Paul Hsieh hash
template <const int DWORDLEN>
unsigned int HsiehHash(const void* pdata)
{
const unsigned short* data = (const unsigned short*)pdata;
unsigned hash = DWORDLEN << 2, tmp;
for (int i = 0; i < DWORDLEN; ++i)
{
hash += data[0];
tmp = (data[1] << 11) ^ hash;
hash = (hash << 16) ^ tmp;
data += 2;
hash += hash >> 11;
}
hash ^= hash << 3;
hash += hash >> 5;
hash ^= hash << 4;
hash += hash >> 17;
hash ^= hash << 25;
hash += hash >> 6;
return (hash);
// Fast Hash
#if !defined (get16bits)
#define get16bits(d) ((((unsigned int)(((const unsigned char *)(d))[1])) << 8)\
+(unsigned int)(((const unsigned char *)(d))[0]) )
#endif
//
// super hash function by Paul Hsieh
//
inline unsigned int HsiehHash (const char * data, int len) {
unsigned int hash = len, tmp;
len>>=2;
/* Main loop */
for (;len > 0; len--) {
hash += get16bits (data);
tmp = (get16bits (data+2) << 11) ^ hash;
hash = (hash << 16) ^ tmp;
data += 2*sizeof (unsigned short);
hash += hash >> 11;
}
/* Force "avalanching" of final 127 bits */
hash ^= hash << 3;
hash += hash >> 5;
hash ^= hash << 4;
hash += hash >> 17;
hash ^= hash << 25;
hash += hash >> 6;
return hash;
}
template <const int CELLSIZE>
@@ -209,6 +220,9 @@ struct btSparseSdf
}
else
{
// printf("c->hash/c[0][1][2]=%d,%d,%d,%d\n", c->hash, c->c[0], c->c[1],c->c[2]);
//printf("h,ixb,iyb,izb=%d,%d,%d,%d\n", h,ix.b, iy.b, iz.b);
c = c->next;
}
}
@@ -334,22 +348,22 @@ struct btSparseSdf
{
struct btS
{
int x, y, z, w;
int x, y, z,w;
void* p;
};
btS myset;
//memset may be needed in case of additional (uninitialized) padding!
//memset(myset, 0, sizeof(btS));
//memset(&myset, 0, sizeof(btS));
myset.x = x;
myset.y = y;
myset.z = z;
myset.w = 0;
myset.p = (void*)shape;
const void* ptr = &myset;
const char* ptr = (const char*)&myset;
unsigned int result = HsiehHash<sizeof(btS) / 4>(ptr);
unsigned int result = HsiehHash(ptr, sizeof(btS) );
return result;
}