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Implemented morton encoding using standard bit-twidling approach.

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This commit is contained in:
David Williams 2015-03-28 09:46:05 +01:00
parent 1c17a7147b
commit d99ed5e624
2 changed files with 23 additions and 16 deletions
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4
include/PolyVox/PagedVolume.h
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@ -127,10 +127,10 @@ namespace PolyVox
VoxelType* getData(void) const; VoxelType* getData(void) const;
uint32_t getDataSizeInBytes(void) const; uint32_t getDataSizeInBytes(void) const;
VoxelType getVoxel(uint16_t uXPos, uint16_t uYPos, uint16_t uZPos) const; VoxelType getVoxel(uint32_t uXPos, uint32_t uYPos, uint32_t uZPos) const;
VoxelType getVoxel(const Vector3DUint16& v3dPos) const; VoxelType getVoxel(const Vector3DUint16& v3dPos) const;
void setVoxel(uint16_t uXPos, uint16_t uYPos, uint16_t uZPos, VoxelType tValue); void setVoxel(uint32_t uXPos, uint32_t uYPos, uint32_t uZPos, VoxelType tValue);
void setVoxel(const Vector3DUint16& v3dPos, VoxelType tValue); void setVoxel(const Vector3DUint16& v3dPos, VoxelType tValue);
private: private:

35
include/PolyVox/PagedVolumeChunk.inl
View File

@ -91,8 +91,19 @@ namespace PolyVox
return m_uSideLength * m_uSideLength * m_uSideLength * sizeof(VoxelType); return m_uSideLength * m_uSideLength * m_uSideLength * sizeof(VoxelType);
} }
// Based on https://fgiesen.wordpress.com/2009/12/13/decoding-morton-codes/
inline uint32_t Part1By2(uint32_t x)
{
x &= 0x000003ff; // x = ---- ---- ---- ---- ---- --98 7654 3210
x = (x ^ (x << 16)) & 0xff0000ff; // x = ---- --98 ---- ---- ---- ---- 7654 3210
x = (x ^ (x << 8)) & 0x0300f00f; // x = ---- --98 ---- ---- 7654 ---- ---- 3210
x = (x ^ (x << 4)) & 0x030c30c3; // x = ---- --98 ---- 76-- --54 ---- 32-- --10
x = (x ^ (x << 2)) & 0x09249249; // x = ---- 9--8 --7- -6-- 5--4 --3- -2-- 1--0
return x;
}
template <typename VoxelType> template <typename VoxelType>
VoxelType PagedVolume<VoxelType>::Chunk::getVoxel(uint16_t uXPos, uint16_t uYPos, uint16_t uZPos) const VoxelType PagedVolume<VoxelType>::Chunk::getVoxel(uint32_t uXPos, uint32_t uYPos, uint32_t uZPos) const
{ {
// This code is not usually expected to be called by the user, with the exception of when implementing paging // This code is not usually expected to be called by the user, with the exception of when implementing paging
// of uncompressed data. It's a performance critical code path so we use asserts rather than exceptions. // of uncompressed data. It's a performance critical code path so we use asserts rather than exceptions.
@ -101,12 +112,10 @@ namespace PolyVox
POLYVOX_ASSERT(uZPos < m_uSideLength, "Supplied position is outside of the chunk"); POLYVOX_ASSERT(uZPos < m_uSideLength, "Supplied position is outside of the chunk");
POLYVOX_ASSERT(m_tData, "No uncompressed data - chunk must be decompressed before accessing voxels."); POLYVOX_ASSERT(m_tData, "No uncompressed data - chunk must be decompressed before accessing voxels.");
return m_tData uint32_t index = 0;
[ index |= Part1By2(uXPos) | Part1By2(uYPos) << 1 | Part1By2(uZPos) << 2;
uXPos +
uYPos * m_uSideLength + return m_tData[index];
uZPos * m_uSideLength * m_uSideLength
];
} }
template <typename VoxelType> template <typename VoxelType>
@ -116,7 +125,7 @@ namespace PolyVox
} }
template <typename VoxelType> template <typename VoxelType>
void PagedVolume<VoxelType>::Chunk::setVoxel(uint16_t uXPos, uint16_t uYPos, uint16_t uZPos, VoxelType tValue) void PagedVolume<VoxelType>::Chunk::setVoxel(uint32_t uXPos, uint32_t uYPos, uint32_t uZPos, VoxelType tValue)
{ {
// This code is not usually expected to be called by the user, with the exception of when implementing paging // This code is not usually expected to be called by the user, with the exception of when implementing paging
// of uncompressed data. It's a performance critical code path so we use asserts rather than exceptions. // of uncompressed data. It's a performance critical code path so we use asserts rather than exceptions.
@ -125,12 +134,10 @@ namespace PolyVox
POLYVOX_ASSERT(uZPos < m_uSideLength, "Supplied position is outside of the chunk"); POLYVOX_ASSERT(uZPos < m_uSideLength, "Supplied position is outside of the chunk");
POLYVOX_ASSERT(m_tData, "No uncompressed data - chunk must be decompressed before accessing voxels."); POLYVOX_ASSERT(m_tData, "No uncompressed data - chunk must be decompressed before accessing voxels.");
m_tData uint32_t index = 0;
[ index |= Part1By2(uXPos) | Part1By2(uYPos) << 1 | Part1By2(uZPos) << 2;
uXPos +
uYPos * m_uSideLength + m_tData[index] = tValue;
uZPos * m_uSideLength * m_uSideLength
] = tValue;
this->m_bDataModified = true; this->m_bDataModified = true;
} }