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Revert "Going back to building key by shifting instead of using bitfield."

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This reverts commit 0d638f98370907b5ffed6b3460e320f4f9b2cf52.
This commit is contained in:
David Williams 2015-03-21 14:40:49 +01:00
parent 0c619ebec7
commit ceeb8f70ce
3 changed files with 38 additions and 30 deletions
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46
include/PolyVox/PagedVolume.h
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@ -281,7 +281,7 @@ namespace PolyVox
PagedVolume& operator=(const PagedVolume& rhs);
private:
/*struct ChunkKey
struct ChunkKey
{
ChunkKey(int32_t x, int32_t y, int32_t z) : iZPos(z), iYPos(y), iXPos(x), iValid(~0) {}
int64_t iZPos : 10;
@ -292,31 +292,39 @@ namespace PolyVox
// so we don't need to have a seperate check for that before using it.
int64_t iValid : 2;
};
static_assert(sizeof(ChunkKey) == sizeof(int64_t), "");*/
static_assert(sizeof(ChunkKey) == sizeof(int64_t), "");
uint64_t posToChunkKey(int32_t iXPos, int32_t iYPos, int32_t iZPos) const
int64_t posToChunkKey(int32_t iXPos, int32_t iYPos, int32_t iZPos) const
{
// Bit-shifting of signed integer values has various issues with undefined or implementation-defined behaviour.
// Therefore we cast to unsigned to avoid these (we only care about the bit pattern anyway, not the actual value).
const uint64_t uXPos = static_cast<uint64_t>(iXPos);
const uint64_t uYPos = static_cast<uint64_t>(iYPos);
const uint64_t uZPos = static_cast<uint64_t>(iZPos);
const uint64_t xKey = ((uXPos >> m_uChunkSideLengthPower) & 0x3FF) << 20;
const uint64_t yKey = ((uYPos >> m_uChunkSideLengthPower) & 0x3FF) << 10;
const uint64_t zKey = ((uZPos >> m_uChunkSideLengthPower) & 0x3FF);
const uint64_t key = 0x80000000 | xKey | yKey | zKey;
return key;
iXPos = iXPos >> m_uChunkSideLengthPower;
iYPos = iYPos >> m_uChunkSideLengthPower;
iZPos = iZPos >> m_uChunkSideLengthPower;
ChunkKey chunkKey(iXPos, iYPos, iZPos);
//chunkKey.iValid = ~0;
//chunkKey.iValid = 2;
// In general, bit shifting signed integers is dubious because of potential undefined or implementation defied behaviour.
// However, it seems that in practice most compilers and architectures work in the same way (http://stackoverflow.com/a/6488645).
static_assert((int64_t(-3) / 4) == 0, "fdfs");
static_assert((int64_t(-3) >> 2) == -1, "fdfs");
/*chunkKey.iXPos = iXPos;
chunkKey.iYPos = iYPos;
chunkKey.iZPos = iZPos;*/
// If this kind of casting ever causes problems there are
// other solutions here: http://stackoverflow.com/a/2468738
int64_t iKeyAsInt64 = force_cast<int64_t>(chunkKey);
return iKeyAsInt64;
}
Chunk* getChunk(uint64_t iKeyAsInt32) const;
Chunk* getChunk(int64_t iKeyAsInt32) const;
mutable uint64_t m_v3dLastAccessedChunkKey = 0;
mutable int64_t m_v3dLastAccessedChunkKey = 0;
mutable Chunk* m_pLastAccessedChunk = nullptr;
mutable std::unordered_map<uint64_t, std::unique_ptr< Chunk > > m_mapChunks;
mutable std::unordered_map<uint32_t, std::unique_ptr< Chunk > > m_mapChunks;
mutable uint32_t m_uTimestamper = 0;

20
include/PolyVox/PagedVolume.inl
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@ -115,7 +115,7 @@ namespace PolyVox
template <typename VoxelType>
VoxelType PagedVolume<VoxelType>::getVoxel(int32_t uXPos, int32_t uYPos, int32_t uZPos) const
{
const uint64_t key = posToChunkKey(uXPos, uYPos, uZPos);
const int64_t key = posToChunkKey(uXPos, uYPos, uZPos);
// Only call get chunk if we can't reuse the chunk pointer from the last voxel access.
auto pChunk = (key == m_v3dLastAccessedChunkKey) ? m_pLastAccessedChunk : getChunk(key);
@ -147,7 +147,7 @@ namespace PolyVox
template <typename VoxelType>
void PagedVolume<VoxelType>::setVoxel(int32_t uXPos, int32_t uYPos, int32_t uZPos, VoxelType tValue)
{
const uint64_t key = posToChunkKey(uXPos, uYPos, uZPos);
const int64_t key = posToChunkKey(uXPos, uYPos, uZPos);
// Only call get chunk if we can't reuse the chunk pointer from the last voxel access.
auto pChunk = (key == m_v3dLastAccessedChunkKey) ? m_pLastAccessedChunk : getChunk(key);
@ -202,7 +202,7 @@ namespace PolyVox
{
for(int32_t z = v3dStart.getZ(); z <= v3dEnd.getZ(); z++)
{
const uint64_t key = posToChunkKey(x, y, z);
const int64_t key = posToChunkKey(x, y, z);
// Note that we don't check against the last chunk here. We're
// not accessing the voxels, we just want to pull them into memory.
@ -256,7 +256,7 @@ namespace PolyVox
{
for(int32_t z = v3dStart.getZ(); z <= v3dEnd.getZ(); z++)
{
const uint64_t key = posToChunkKey(x, y, z);
const int64_t key = posToChunkKey(x, y, z);
m_mapChunks.erase(key);
}
}
@ -264,7 +264,7 @@ namespace PolyVox
}
template <typename VoxelType>
typename PagedVolume<VoxelType>::Chunk* PagedVolume<VoxelType>::getChunk(uint64_t iKeyAsInt32) const
typename PagedVolume<VoxelType>::Chunk* PagedVolume<VoxelType>::getChunk(int64_t iKeyAsInt32) const
{
// This function is relatively large and slow because it involves searching for a chunk and creating it if it is not found. A natural
// optimization is to only do this work if the chunk we are accessing is not the same as the last chunk we accessed (which it usually
@ -293,14 +293,14 @@ namespace PolyVox
// If we still haven't found the chunk then it's time to create a new one and page it in from disk.
if (!pChunk)
{
const int32_t uChunkX = (iKeyAsInt32 >> 20) & 0x3FF;
const int32_t uChunkY = (iKeyAsInt32 >> 10) & 0x3FF;
const int32_t uChunkZ = (iKeyAsInt32) & 0x3FF;
/*const int32_t uChunkX = (key >> 20) & 0x3FF;
const int32_t uChunkY = (key >> 10) & 0x3FF;
const int32_t uChunkZ = (key ) & 0x3FF;*/
// The chunk was not found so we will create a new one.
/*ChunkKeyConverter converter;
converter.i = key;*/
//ChunkKey realKey = force_cast<ChunkKey>(iKeyAsInt32);
Vector3DInt32 v3dChunkPos(uChunkX, uChunkY, uChunkZ);
ChunkKey realKey = force_cast<ChunkKey>(iKeyAsInt32);
Vector3DInt32 v3dChunkPos(realKey.iXPos, realKey.iYPos, realKey.iZPos);
pChunk = new PagedVolume<VoxelType>::Chunk(v3dChunkPos, m_uChunkSideLength, m_pPager);
pChunk->m_uChunkLastAccessed = ++m_uTimestamper; // Important, as we may soon delete the oldest chunk
m_mapChunks.insert(std::make_pair(iKeyAsInt32, std::unique_ptr<Chunk>(pChunk)));

2
include/PolyVox/PagedVolumeSampler.inl
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@ -97,7 +97,7 @@ namespace PolyVox
// Base version updates position and validity flags.
BaseVolume<VoxelType>::template Sampler< PagedVolume<VoxelType> >::setPosition(xPos, yPos, zPos);
const uint64_t key = this->mVolume->posToChunkKey(xPos, yPos, zPos);
const int32_t key = this->mVolume->posToChunkKey(xPos, yPos, zPos);
// Then we update the voxel pointer.
auto pCurrentChunk = (key == this->mVolume->m_v3dLastAccessedChunkKey) ? this->mVolume->m_pLastAccessedChunk : this->mVolume->getChunk(key);