Split the code which generates vertices and indices for a single cell into a separate function.
This commit is contained in:
David Williams
parent
f32bb1d1ed
commit
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@ -49,92 +49,13 @@ namespace PolyVox
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template< typename VolumeType, typename MeshType, typename ControllerType >
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template< typename VolumeType, typename MeshType, typename ControllerType >
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void extractMarchingCubesMeshCustom(VolumeType* volData, Region region, MeshType* result, ControllerType controller)
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void generateMeshForCell(Region& region, MeshType* result, ControllerType& controller, typename VolumeType::Sampler& sampler, Array<2, Vector3DInt32>& pIndices, Array<2, Vector3DInt32>& pPreviousIndices, uint8_t iCubeIndex, uint32_t uXRegSpace, uint32_t uYRegSpace, uint32_t uZRegSpace, typename ControllerType::DensityType tThreshold)
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{
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POLYVOX_THROW_IF(result == nullptr, std::invalid_argument, "Provided mesh cannot be null");
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Timer timer;
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result->clear();
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typename ControllerType::DensityType tThreshold = controller.getThreshold();
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const uint32_t uRegionWidthInVoxels = region.getWidthInVoxels();
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const uint32_t uRegionHeightInVoxels = region.getHeightInVoxels();
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const uint32_t uRegionDepthInVoxels = region.getDepthInVoxels();
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// No need to clear memory because we only read from elements we have written to.
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Array<2, Vector3DInt32> pIndices(uRegionWidthInVoxels, uRegionHeightInVoxels);
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Array<2, Vector3DInt32> pPreviousIndices(uRegionWidthInVoxels, uRegionHeightInVoxels);
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Array2DUint8 pPreviousSliceBitmask(uRegionWidthInVoxels, uRegionHeightInVoxels);
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Array1DUint8 pPreviousRowBitmask(uRegionWidthInVoxels);
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uint8_t uPreviousCell = 0;
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typename VolumeType::Sampler startOfSlice(volData);
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startOfSlice.setPosition(region.getLowerX(), region.getLowerY(), region.getLowerZ());
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for (uint32_t uZRegSpace = 0; uZRegSpace < uRegionDepthInVoxels; uZRegSpace++)
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{
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typename VolumeType::Sampler startOfRow = startOfSlice;
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for (uint32_t uYRegSpace = 0; uYRegSpace < uRegionHeightInVoxels; uYRegSpace++)
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{
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// Copying a sampler which is already pointing at the correct location seems (slightly) faster than
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// calling setPosition(). Therefore we make use of 'startOfRow' and 'startOfSlice' to reset the sampler.
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typename VolumeType::Sampler sampler = startOfRow;
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for (uint32_t uXRegSpace = 0; uXRegSpace < uRegionWidthInVoxels; uXRegSpace++)
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{
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// Note: In many cases the provided region will be (mostly) empty which means mesh vertices/indices
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// are not generated and the only thing that is done for each cell is the computation of iCubeIndex.
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// It appears that retriving the voxel value is not so expensive and that it is the bitwise combining
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// which actually carries the cost.
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//
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// If we really need to speed this up more then it may be possible to pack 4 8-bit cell indices into
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// a single 32-bit value and then perform the bitwise logic on all four of them at the same time.
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// However, this complicates the code and there would still be the cost of packing/unpacking so it's
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// not clear if there is really a benefit. It's something to consider in the future.
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uint8_t iCubeIndex = 0;
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// Four bits of our cube index are obtained by looking at the cube index for
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// the previous slice and copying four of those bits into their new positions.
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uint8_t iPreviousCubeIndexZ = pPreviousSliceBitmask(uXRegSpace, uYRegSpace);
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iPreviousCubeIndexZ >>= 4;
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iCubeIndex |= iPreviousCubeIndexZ;
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// Two bits of our cube index are obtained by looking at the cube index for
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// the previous row and copying two of those bits into their new positions.
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uint8_t iPreviousCubeIndexY = pPreviousRowBitmask(uXRegSpace);
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iPreviousCubeIndexY &= 204; //204 = 128+64+8+4
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iPreviousCubeIndexY >>= 2;
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iCubeIndex |= iPreviousCubeIndexY;
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// One bit of our cube index are obtained by looking at the cube index for
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// the previous cell and copying one of those bits into it's new position.
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uint8_t iPreviousCubeIndexX = uPreviousCell;
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iPreviousCubeIndexX &= 170; //170 = 128+32+8+2
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iPreviousCubeIndexX >>= 1;
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iCubeIndex |= iPreviousCubeIndexX;
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// The last bit of our cube index is obtained by looking
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// at the relevant voxel and comparing it to the threshold
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typename VolumeType::VoxelType v111 = sampler.getVoxel();
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if (controller.convertToDensity(v111) < tThreshold) iCubeIndex |= 128;
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// The current value becomes the previous value, ready for the next iteration.
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uPreviousCell = iCubeIndex;
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pPreviousRowBitmask(uXRegSpace) = iCubeIndex;
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pPreviousSliceBitmask(uXRegSpace, uYRegSpace) = iCubeIndex;
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/* Cube is entirely in/out of the surface */
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uint16_t uEdge = edgeTable[iCubeIndex];
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if (uEdge != 0)
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{
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{
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auto v111 = sampler.getVoxel();
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auto v111Density = controller.convertToDensity(v111);
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auto v111Density = controller.convertToDensity(v111);
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const Vector3DFloat n000 = computeCentralDifferenceGradient(sampler, controller);
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const Vector3DFloat n000 = computeCentralDifferenceGradient(sampler, controller);
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uint16_t uEdge = edgeTable[iCubeIndex];
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/* Find the vertices where the surface intersects the cube */
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/* Find the vertices where the surface intersects the cube */
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if ((uEdge & 64) && (uXRegSpace > 0))
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if ((uEdge & 64) && (uXRegSpace > 0))
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{
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{
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@ -311,6 +232,99 @@ namespace PolyVox
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}
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}
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} // For each triangle
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} // For each triangle
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}
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}
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}
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template< typename VolumeType, typename MeshType, typename ControllerType >
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void extractMarchingCubesMeshCustom(VolumeType* volData, Region region, MeshType* result, ControllerType controller)
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{
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POLYVOX_THROW_IF(result == nullptr, std::invalid_argument, "Provided mesh cannot be null");
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Timer timer;
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result->clear();
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typename ControllerType::DensityType tThreshold = controller.getThreshold();
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const uint32_t uRegionWidthInVoxels = region.getWidthInVoxels();
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const uint32_t uRegionHeightInVoxels = region.getHeightInVoxels();
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const uint32_t uRegionDepthInVoxels = region.getDepthInVoxels();
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// No need to clear memory because we only read from elements we have written to.
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Array<2, Vector3DInt32> pIndices(uRegionWidthInVoxels, uRegionHeightInVoxels);
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Array<2, Vector3DInt32> pPreviousIndices(uRegionWidthInVoxels, uRegionHeightInVoxels);
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Array2DUint8 pPreviousSliceBitmask(uRegionWidthInVoxels, uRegionHeightInVoxels);
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Array1DUint8 pPreviousRowBitmask(uRegionWidthInVoxels);
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uint8_t uPreviousCell = 0;
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typename VolumeType::Sampler startOfSlice(volData);
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startOfSlice.setPosition(region.getLowerX(), region.getLowerY(), region.getLowerZ());
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for (uint32_t uZRegSpace = 0; uZRegSpace < uRegionDepthInVoxels; uZRegSpace++)
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{
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typename VolumeType::Sampler startOfRow = startOfSlice;
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for (uint32_t uYRegSpace = 0; uYRegSpace < uRegionHeightInVoxels; uYRegSpace++)
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{
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// Copying a sampler which is already pointing at the correct location seems (slightly) faster than
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// calling setPosition(). Therefore we make use of 'startOfRow' and 'startOfSlice' to reset the sampler.
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typename VolumeType::Sampler sampler = startOfRow;
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for (uint32_t uXRegSpace = 0; uXRegSpace < uRegionWidthInVoxels; uXRegSpace++)
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{
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// Note: In many cases the provided region will be (mostly) empty which means mesh vertices/indices
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// are not generated and the only thing that is done for each cell is the computation of iCubeIndex.
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// It appears that retriving the voxel value is not so expensive and that it is the bitwise combining
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// which actually carries the cost.
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//
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// If we really need to speed this up more then it may be possible to pack 4 8-bit cell indices into
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// a single 32-bit value and then perform the bitwise logic on all four of them at the same time.
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// However, this complicates the code and there would still be the cost of packing/unpacking so it's
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// not clear if there is really a benefit. It's something to consider in the future.
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uint8_t iCubeIndex = 0;
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// Four bits of our cube index are obtained by looking at the cube index for
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// the previous slice and copying four of those bits into their new positions.
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uint8_t iPreviousCubeIndexZ = pPreviousSliceBitmask(uXRegSpace, uYRegSpace);
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iPreviousCubeIndexZ >>= 4;
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iCubeIndex |= iPreviousCubeIndexZ;
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// Two bits of our cube index are obtained by looking at the cube index for
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// the previous row and copying two of those bits into their new positions.
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uint8_t iPreviousCubeIndexY = pPreviousRowBitmask(uXRegSpace);
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iPreviousCubeIndexY &= 204; //204 = 128+64+8+4
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iPreviousCubeIndexY >>= 2;
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iCubeIndex |= iPreviousCubeIndexY;
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// One bit of our cube index are obtained by looking at the cube index for
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// the previous cell and copying one of those bits into it's new position.
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uint8_t iPreviousCubeIndexX = uPreviousCell;
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iPreviousCubeIndexX &= 170; //170 = 128+32+8+2
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iPreviousCubeIndexX >>= 1;
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iCubeIndex |= iPreviousCubeIndexX;
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// The last bit of our cube index is obtained by looking
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// at the relevant voxel and comparing it to the threshold
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typename VolumeType::VoxelType v111 = sampler.getVoxel();
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if (controller.convertToDensity(v111) < tThreshold) iCubeIndex |= 128;
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// The current value becomes the previous value, ready for the next iteration.
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uPreviousCell = iCubeIndex;
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pPreviousRowBitmask(uXRegSpace) = iCubeIndex;
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pPreviousSliceBitmask(uXRegSpace, uYRegSpace) = iCubeIndex;
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/* Cube is entirely in/out of the surface */
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if (edgeTable[iCubeIndex] != 0)
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{
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// This is a rather ugly function call and appears to have some cost compared to inlining the code.
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// As a result the case when a cell contains vertices/indices is slightly slower, but the (more common)
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// case where a cell is empty is slightly faster, probably because the main loop is a lot more compact.
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// Having a seperate function will also make it easier to profile in the future and see whether empty or
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// occupied cells are really the bottleneck. The large number of parameters is messy though, so it
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// would be nice to reduce these if we can work out how.
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generateMeshForCell<VolumeType, MeshType, ControllerType>(region, result, controller,
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sampler, pIndices, pPreviousIndices, iCubeIndex, uXRegSpace, uYRegSpace, uZRegSpace, tThreshold);
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} // For each cell
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} // For each cell
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sampler.movePositiveX();
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sampler.movePositiveX();
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} // For X
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} // For X
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