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diff --git a/libs/assimp/code/Common/VertexTriangleAdjacency.cpp b/libs/assimp/code/Common/VertexTriangleAdjacency.cpp
new file mode 100644
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+++ b/libs/assimp/code/Common/VertexTriangleAdjacency.cpp
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+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2022, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file Implementation of the VertexTriangleAdjacency helper class
+ */
+
+// internal headers
+#include "VertexTriangleAdjacency.h"
+#include <assimp/mesh.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+VertexTriangleAdjacency::VertexTriangleAdjacency(aiFace *pcFaces,
+        unsigned int iNumFaces,
+        unsigned int iNumVertices /*= 0*/,
+        bool bComputeNumTriangles /*= false*/) {
+    // compute the number of referenced vertices if it wasn't specified by the caller
+    const aiFace *const pcFaceEnd = pcFaces + iNumFaces;
+    if (0 == iNumVertices) {
+        for (aiFace *pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace) {
+            ai_assert(nullptr != pcFace);
+            ai_assert(3 == pcFace->mNumIndices);
+            iNumVertices = std::max(iNumVertices, pcFace->mIndices[0]);
+            iNumVertices = std::max(iNumVertices, pcFace->mIndices[1]);
+            iNumVertices = std::max(iNumVertices, pcFace->mIndices[2]);
+        }
+    }
+
+    mNumVertices = iNumVertices + 1;
+
+    unsigned int *pi;
+
+    // allocate storage
+    if (bComputeNumTriangles) {
+        pi = mLiveTriangles = new unsigned int[iNumVertices + 1];
+        ::memset(mLiveTriangles, 0, sizeof(unsigned int) * (iNumVertices + 1));
+        mOffsetTable = new unsigned int[iNumVertices + 2] + 1;
+    } else {
+        pi = mOffsetTable = new unsigned int[iNumVertices + 2] + 1;
+        ::memset(mOffsetTable, 0, sizeof(unsigned int) * (iNumVertices + 1));
+        mLiveTriangles = nullptr; // important, otherwise the d'tor would crash
+    }
+
+    // get a pointer to the end of the buffer
+    unsigned int *piEnd = pi + iNumVertices;
+    *piEnd++ = 0u;
+
+    // first pass: compute the number of faces referencing each vertex
+    for (aiFace *pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace) {
+        unsigned nind = pcFace->mNumIndices;
+        unsigned *ind = pcFace->mIndices;
+        if (nind > 0) pi[ind[0]]++;
+        if (nind > 1) pi[ind[1]]++;
+        if (nind > 2) pi[ind[2]]++;
+    }
+
+    // second pass: compute the final offset table
+    unsigned int iSum = 0;
+    unsigned int *piCurOut = this->mOffsetTable;
+    for (unsigned int *piCur = pi; piCur != piEnd; ++piCur, ++piCurOut) {
+
+        unsigned int iLastSum = iSum;
+        iSum += *piCur;
+        *piCurOut = iLastSum;
+    }
+    pi = this->mOffsetTable;
+
+    // third pass: compute the final table
+    this->mAdjacencyTable = new unsigned int[iSum];
+    iSum = 0;
+    for (aiFace *pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace, ++iSum) {
+        unsigned nind = pcFace->mNumIndices;
+        unsigned *ind = pcFace->mIndices;
+
+        if (nind > 0) mAdjacencyTable[pi[ind[0]]++] = iSum;
+        if (nind > 1) mAdjacencyTable[pi[ind[1]]++] = iSum;
+        if (nind > 2) mAdjacencyTable[pi[ind[2]]++] = iSum;
+    }
+    // fourth pass: undo the offset computations made during the third pass
+    // We could do this in a separate buffer, but this would be TIMES slower.
+    --mOffsetTable;
+    *mOffsetTable = 0u;
+}
+// ------------------------------------------------------------------------------------------------
+VertexTriangleAdjacency::~VertexTriangleAdjacency() {
+    // delete allocated storage
+    delete[] mOffsetTable;
+    delete[] mAdjacencyTable;
+    delete[] mLiveTriangles;
+}