123 lines
3.3 KiB
C++
123 lines
3.3 KiB
C++
/*
|
|
Bullet Continuous Collision Detection and Physics Library
|
|
Copyright (c) 2003-2006 Erwin Coumans https://bulletphysics.org
|
|
|
|
This software is provided 'as-is', without any express or implied warranty.
|
|
In no event will the authors be held liable for any damages arising from the use of this software.
|
|
Permission is granted to anyone to use this software for any purpose,
|
|
including commercial applications, and to alter it and redistribute it freely,
|
|
subject to the following restrictions:
|
|
|
|
1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
|
|
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
|
|
3. This notice may not be removed or altered from any source distribution.
|
|
*/
|
|
|
|
#ifndef BT_UNION_FIND_H
|
|
#define BT_UNION_FIND_H
|
|
|
|
#include "LinearMath/btAlignedObjectArray.h"
|
|
|
|
#define USE_PATH_COMPRESSION 1
|
|
|
|
///see for discussion of static island optimizations by Vroonsh here: http://code.google.com/p/bullet/issues/detail?id=406
|
|
#define STATIC_SIMULATION_ISLAND_OPTIMIZATION 1
|
|
|
|
struct btElement
|
|
{
|
|
int m_id;
|
|
int m_sz;
|
|
};
|
|
|
|
///UnionFind calculates connected subsets
|
|
// Implements weighted Quick Union with path compression
|
|
// optimization: could use short ints instead of ints (halving memory, would limit the number of rigid bodies to 64k, sounds reasonable)
|
|
class btUnionFind
|
|
{
|
|
private:
|
|
btAlignedObjectArray<btElement> m_elements;
|
|
|
|
public:
|
|
btUnionFind();
|
|
~btUnionFind();
|
|
|
|
//this is a special operation, destroying the content of btUnionFind.
|
|
//it sorts the elements, based on island id, in order to make it easy to iterate over islands
|
|
void sortIslands();
|
|
|
|
void reset(int N);
|
|
|
|
SIMD_FORCE_INLINE int getNumElements() const
|
|
{
|
|
return int(m_elements.size());
|
|
}
|
|
SIMD_FORCE_INLINE bool isRoot(int x) const
|
|
{
|
|
return (x == m_elements[x].m_id);
|
|
}
|
|
|
|
btElement& getElement(int index)
|
|
{
|
|
return m_elements[index];
|
|
}
|
|
const btElement& getElement(int index) const
|
|
{
|
|
return m_elements[index];
|
|
}
|
|
|
|
void allocate(int N);
|
|
void Free();
|
|
|
|
int find(int p, int q)
|
|
{
|
|
return (find(p) == find(q));
|
|
}
|
|
|
|
void unite(int p, int q)
|
|
{
|
|
int i = find(p), j = find(q);
|
|
if (i == j)
|
|
return;
|
|
|
|
#ifndef USE_PATH_COMPRESSION
|
|
//weighted quick union, this keeps the 'trees' balanced, and keeps performance of unite O( log(n) )
|
|
if (m_elements[i].m_sz < m_elements[j].m_sz)
|
|
{
|
|
m_elements[i].m_id = j;
|
|
m_elements[j].m_sz += m_elements[i].m_sz;
|
|
}
|
|
else
|
|
{
|
|
m_elements[j].m_id = i;
|
|
m_elements[i].m_sz += m_elements[j].m_sz;
|
|
}
|
|
#else
|
|
m_elements[i].m_id = j;
|
|
m_elements[j].m_sz += m_elements[i].m_sz;
|
|
#endif //USE_PATH_COMPRESSION
|
|
}
|
|
|
|
int find(int x)
|
|
{
|
|
//btAssert(x < m_N);
|
|
//btAssert(x >= 0);
|
|
|
|
while (x != m_elements[x].m_id)
|
|
{
|
|
//not really a reason not to use path compression, and it flattens the trees/improves find performance dramatically
|
|
|
|
#ifdef USE_PATH_COMPRESSION
|
|
const btElement* elementPtr = &m_elements[m_elements[x].m_id];
|
|
m_elements[x].m_id = elementPtr->m_id;
|
|
x = elementPtr->m_id;
|
|
#else //
|
|
x = m_elements[x].m_id;
|
|
#endif
|
|
//btAssert(x < m_N);
|
|
//btAssert(x >= 0);
|
|
}
|
|
return x;
|
|
}
|
|
};
|
|
|
|
#endif //BT_UNION_FIND_H
|