64 lines
2.1 KiB
C++
64 lines
2.1 KiB
C++
// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
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// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
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// SPDX-License-Identifier: MIT
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#include <Jolt/Jolt.h>
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#include <Jolt/TriangleSplitter/TriangleSplitterMorton.h>
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#include <Jolt/Geometry/MortonCode.h>
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#include <Jolt/Core/QuickSort.h>
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JPH_NAMESPACE_BEGIN
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TriangleSplitterMorton::TriangleSplitterMorton(const VertexList &inVertices, const IndexedTriangleList &inTriangles) :
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TriangleSplitter(inVertices, inTriangles)
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{
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// Calculate bounds of centroids
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AABox bounds;
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for (uint t = 0; t < inTriangles.size(); ++t)
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bounds.Encapsulate(Vec3(mCentroids[t]));
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// Make sure box is not degenerate
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bounds.EnsureMinimalEdgeLength(1.0e-5f);
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// Calculate morton codes
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mMortonCodes.resize(inTriangles.size());
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for (uint t = 0; t < inTriangles.size(); ++t)
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mMortonCodes[t] = MortonCode::sGetMortonCode(Vec3(mCentroids[t]), bounds);
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// Sort triangles on morton code
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const Array<uint32> &morton_codes = mMortonCodes;
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QuickSort(mSortedTriangleIdx.begin(), mSortedTriangleIdx.end(), [&morton_codes](uint inLHS, uint inRHS) { return morton_codes[inLHS] < morton_codes[inRHS]; });
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}
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bool TriangleSplitterMorton::Split(const Range &inTriangles, Range &outLeft, Range &outRight)
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{
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uint32 first_code = mMortonCodes[mSortedTriangleIdx[inTriangles.mBegin]];
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uint32 last_code = mMortonCodes[mSortedTriangleIdx[inTriangles.mEnd - 1]];
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uint common_prefix = CountLeadingZeros(first_code ^ last_code);
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// Use binary search to find where the next bit differs
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uint split = inTriangles.mBegin; // Initial guess
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uint step = inTriangles.Count();
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do
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{
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step = (step + 1) >> 1; // Exponential decrease
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uint new_split = split + step; // Proposed new position
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if (new_split < inTriangles.mEnd)
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{
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uint32 split_code = mMortonCodes[mSortedTriangleIdx[new_split]];
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uint split_prefix = CountLeadingZeros(first_code ^ split_code);
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if (split_prefix > common_prefix)
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split = new_split; // Accept proposal
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}
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}
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while (step > 1);
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outLeft = Range(inTriangles.mBegin, split + 1);
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outRight = Range(split + 1, inTriangles.mEnd);
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return outLeft.Count() > 0 && outRight.Count() > 0;
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}
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JPH_NAMESPACE_END
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