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Switched to using lookup tables for Morton encoding.

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This commit is contained in:
David Williams
2015-03-29 00:17:27 +01:00
parent d99ed5e624
commit d3b2dab1ac
2 changed files with 165 additions and 17 deletions
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23
include/PolyVox/PagedVolumeChunk.inl
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@ -21,6 +21,7 @@ freely, subject to the following restrictions:
distribution.
*******************************************************************************/
#include "PolyVox/Impl/Morton.h"
#include "PolyVox/Impl/Utility.h"
namespace PolyVox
@ -36,6 +37,7 @@ namespace PolyVox
,m_v3dChunkSpacePosition(v3dPosition)
{
POLYVOX_ASSERT(m_pPager, "No valid pager supplied to chunk constructor.");
POLYVOX_ASSERT(uSideLength <= 256, "Chunk side length cannot be greater than 256.");
// Compute the side length
m_uSideLength = uSideLength;
@ -91,29 +93,17 @@ namespace PolyVox
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>
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
// 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.
POLYVOX_ASSERT(uXPos < m_uSideLength, "Supplied position is outside of the chunk");
POLYVOX_ASSERT(uYPos < 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.");
uint32_t index = 0;
index |= Part1By2(uXPos) | Part1By2(uYPos) << 1 | Part1By2(uZPos) << 2;
uint32_t index = morton256_x[uXPos] | morton256_y[uYPos] | morton256_z[uZPos];
return m_tData[index];
}
@ -128,14 +118,13 @@ namespace PolyVox
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
// 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.
POLYVOX_ASSERT(uXPos < m_uSideLength, "Supplied position is outside of the chunk");
POLYVOX_ASSERT(uYPos < 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.");
uint32_t index = 0;
index |= Part1By2(uXPos) | Part1By2(uYPos) << 1 | Part1By2(uZPos) << 2;
uint32_t index = morton256_x[uXPos] | morton256_y[uYPos] | morton256_z[uZPos];
m_tData[index] = tValue;