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diff --git a/libs/assimp/code/PostProcessing/CalcTangentsProcess.cpp b/libs/assimp/code/PostProcessing/CalcTangentsProcess.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 post processing step to calculate
+ *  tangents and bitangents for all imported meshes
+ */
+
+// internal headers
+#include "CalcTangentsProcess.h"
+#include "ProcessHelper.h"
+#include <assimp/TinyFormatter.h>
+#include <assimp/qnan.h>
+
+using namespace Assimp;
+
+// ------------------------------------------------------------------------------------------------
+// Constructor to be privately used by Importer
+CalcTangentsProcess::CalcTangentsProcess() :
+        configMaxAngle(float(AI_DEG_TO_RAD(45.f))), configSourceUV(0) {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Destructor, private as well
+CalcTangentsProcess::~CalcTangentsProcess() {
+    // nothing to do here
+}
+
+// ------------------------------------------------------------------------------------------------
+// Returns whether the processing step is present in the given flag field.
+bool CalcTangentsProcess::IsActive(unsigned int pFlags) const {
+    return (pFlags & aiProcess_CalcTangentSpace) != 0;
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void CalcTangentsProcess::SetupProperties(const Importer *pImp) {
+    ai_assert(nullptr != pImp);
+
+    // get the current value of the property
+    configMaxAngle = pImp->GetPropertyFloat(AI_CONFIG_PP_CT_MAX_SMOOTHING_ANGLE, 45.f);
+    configMaxAngle = std::max(std::min(configMaxAngle, 45.0f), 0.0f);
+    configMaxAngle = AI_DEG_TO_RAD(configMaxAngle);
+
+    configSourceUV = pImp->GetPropertyInteger(AI_CONFIG_PP_CT_TEXTURE_CHANNEL_INDEX, 0);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Executes the post processing step on the given imported data.
+void CalcTangentsProcess::Execute(aiScene *pScene) {
+    ai_assert(nullptr != pScene);
+
+    ASSIMP_LOG_DEBUG("CalcTangentsProcess begin");
+
+    bool bHas = false;
+    for (unsigned int a = 0; a < pScene->mNumMeshes; a++) {
+        if (ProcessMesh(pScene->mMeshes[a], a)) bHas = true;
+    }
+
+    if (bHas) {
+        ASSIMP_LOG_INFO("CalcTangentsProcess finished. Tangents have been calculated");
+    } else {
+        ASSIMP_LOG_DEBUG("CalcTangentsProcess finished");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+// Calculates tangents and bi-tangents for the given mesh
+bool CalcTangentsProcess::ProcessMesh(aiMesh *pMesh, unsigned int meshIndex) {
+    // we assume that the mesh is still in the verbose vertex format where each face has its own set
+    // of vertices and no vertices are shared between faces. Sadly I don't know any quick test to
+    // assert() it here.
+    // assert( must be verbose, dammit);
+
+    if (pMesh->mTangents) // this implies that mBitangents is also there
+        return false;
+
+    // If the mesh consists of lines and/or points but not of
+    // triangles or higher-order polygons the normal vectors
+    // are undefined.
+    if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON))) {
+        ASSIMP_LOG_INFO("Tangents are undefined for line and point meshes");
+        return false;
+    }
+
+    // what we can check, though, is if the mesh has normals and texture coordinates. That's a requirement
+    if (pMesh->mNormals == nullptr) {
+        ASSIMP_LOG_ERROR("Failed to compute tangents; need normals");
+        return false;
+    }
+    if (configSourceUV >= AI_MAX_NUMBER_OF_TEXTURECOORDS || !pMesh->mTextureCoords[configSourceUV]) {
+        ASSIMP_LOG_ERROR("Failed to compute tangents; need UV data in channel", configSourceUV);
+        return false;
+    }
+
+    const float angleEpsilon = 0.9999f;
+
+    std::vector<bool> vertexDone(pMesh->mNumVertices, false);
+    const float qnan = get_qnan();
+
+    // create space for the tangents and bitangents
+    pMesh->mTangents = new aiVector3D[pMesh->mNumVertices];
+    pMesh->mBitangents = new aiVector3D[pMesh->mNumVertices];
+
+    const aiVector3D *meshPos = pMesh->mVertices;
+    const aiVector3D *meshNorm = pMesh->mNormals;
+    const aiVector3D *meshTex = pMesh->mTextureCoords[configSourceUV];
+    aiVector3D *meshTang = pMesh->mTangents;
+    aiVector3D *meshBitang = pMesh->mBitangents;
+
+    // calculate the tangent and bitangent for every face
+    for (unsigned int a = 0; a < pMesh->mNumFaces; a++) {
+        const aiFace &face = pMesh->mFaces[a];
+        if (face.mNumIndices < 3) {
+            // There are less than three indices, thus the tangent vector
+            // is not defined. We are finished with these vertices now,
+            // their tangent vectors are set to qnan.
+            for (unsigned int i = 0; i < face.mNumIndices; ++i) {
+                unsigned int idx = face.mIndices[i];
+                vertexDone[idx] = true;
+                meshTang[idx] = aiVector3D(qnan);
+                meshBitang[idx] = aiVector3D(qnan);
+            }
+
+            continue;
+        }
+
+        // triangle or polygon... we always use only the first three indices. A polygon
+        // is supposed to be planar anyways....
+        // FIXME: (thom) create correct calculation for multi-vertex polygons maybe?
+        const unsigned int p0 = face.mIndices[0], p1 = face.mIndices[1], p2 = face.mIndices[2];
+
+        // position differences p1->p2 and p1->p3
+        aiVector3D v = meshPos[p1] - meshPos[p0], w = meshPos[p2] - meshPos[p0];
+
+        // texture offset p1->p2 and p1->p3
+        float sx = meshTex[p1].x - meshTex[p0].x, sy = meshTex[p1].y - meshTex[p0].y;
+        float tx = meshTex[p2].x - meshTex[p0].x, ty = meshTex[p2].y - meshTex[p0].y;
+        float dirCorrection = (tx * sy - ty * sx) < 0.0f ? -1.0f : 1.0f;
+        // when t1, t2, t3 in same position in UV space, just use default UV direction.
+        if (sx * ty == sy * tx) {
+            sx = 0.0;
+            sy = 1.0;
+            tx = 1.0;
+            ty = 0.0;
+        }
+
+        // tangent points in the direction where to positive X axis of the texture coord's would point in model space
+        // bitangent's points along the positive Y axis of the texture coord's, respectively
+        aiVector3D tangent, bitangent;
+        tangent.x = (w.x * sy - v.x * ty) * dirCorrection;
+        tangent.y = (w.y * sy - v.y * ty) * dirCorrection;
+        tangent.z = (w.z * sy - v.z * ty) * dirCorrection;
+        bitangent.x = (- w.x * sx + v.x * tx) * dirCorrection;
+        bitangent.y = (- w.y * sx + v.y * tx) * dirCorrection;
+        bitangent.z = (- w.z * sx + v.z * tx) * dirCorrection;
+
+        // store for every vertex of that face
+        for (unsigned int b = 0; b < face.mNumIndices; ++b) {
+            unsigned int p = face.mIndices[b];
+
+            // project tangent and bitangent into the plane formed by the vertex' normal
+            aiVector3D localTangent = tangent - meshNorm[p] * (tangent * meshNorm[p]);
+            aiVector3D localBitangent = bitangent - meshNorm[p] * (bitangent * meshNorm[p]) - localTangent * (bitangent * localTangent);
+            localTangent.NormalizeSafe();
+            localBitangent.NormalizeSafe();
+
+            // reconstruct tangent/bitangent according to normal and bitangent/tangent when it's infinite or NaN.
+            bool invalid_tangent = is_special_float(localTangent.x) || is_special_float(localTangent.y) || is_special_float(localTangent.z);
+            bool invalid_bitangent = is_special_float(localBitangent.x) || is_special_float(localBitangent.y) || is_special_float(localBitangent.z);
+            if (invalid_tangent != invalid_bitangent) {
+                if (invalid_tangent) {
+                    localTangent = meshNorm[p] ^ localBitangent;
+                    localTangent.NormalizeSafe();
+                } else {
+                    localBitangent = localTangent ^ meshNorm[p];
+                    localBitangent.NormalizeSafe();
+                }
+            }
+
+            // and write it into the mesh.
+            meshTang[p] = localTangent;
+            meshBitang[p] = localBitangent;
+        }
+    }
+
+    // create a helper to quickly find locally close vertices among the vertex array
+    // FIX: check whether we can reuse the SpatialSort of a previous step
+    SpatialSort *vertexFinder = nullptr;
+    SpatialSort _vertexFinder;
+    float posEpsilon = 10e-6f;
+    if (shared) {
+        std::vector<std::pair<SpatialSort, float>> *avf;
+        shared->GetProperty(AI_SPP_SPATIAL_SORT, avf);
+        if (avf) {
+            std::pair<SpatialSort, float> &blubb = avf->operator[](meshIndex);
+            vertexFinder = &blubb.first;
+            posEpsilon = blubb.second;
+            ;
+        }
+    }
+    if (!vertexFinder) {
+        _vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof(aiVector3D));
+        vertexFinder = &_vertexFinder;
+        posEpsilon = ComputePositionEpsilon(pMesh);
+    }
+    std::vector<unsigned int> verticesFound;
+
+    const float fLimit = std::cos(configMaxAngle);
+    std::vector<unsigned int> closeVertices;
+
+    // in the second pass we now smooth out all tangents and bitangents at the same local position
+    // if they are not too far off.
+    for (unsigned int a = 0; a < pMesh->mNumVertices; a++) {
+        if (vertexDone[a])
+            continue;
+
+        const aiVector3D &origPos = pMesh->mVertices[a];
+        const aiVector3D &origNorm = pMesh->mNormals[a];
+        const aiVector3D &origTang = pMesh->mTangents[a];
+        const aiVector3D &origBitang = pMesh->mBitangents[a];
+        closeVertices.resize(0);
+
+        // find all vertices close to that position
+        vertexFinder->FindPositions(origPos, posEpsilon, verticesFound);
+
+        closeVertices.reserve(verticesFound.size() + 5);
+        closeVertices.push_back(a);
+
+        // look among them for other vertices sharing the same normal and a close-enough tangent/bitangent
+        for (unsigned int b = 0; b < verticesFound.size(); b++) {
+            unsigned int idx = verticesFound[b];
+            if (vertexDone[idx])
+                continue;
+            if (meshNorm[idx] * origNorm < angleEpsilon)
+                continue;
+            if (meshTang[idx] * origTang < fLimit)
+                continue;
+            if (meshBitang[idx] * origBitang < fLimit)
+                continue;
+
+            // it's similar enough -> add it to the smoothing group
+            closeVertices.push_back(idx);
+            vertexDone[idx] = true;
+        }
+
+        // smooth the tangents and bitangents of all vertices that were found to be close enough
+        aiVector3D smoothTangent(0, 0, 0), smoothBitangent(0, 0, 0);
+        for (unsigned int b = 0; b < closeVertices.size(); ++b) {
+            smoothTangent += meshTang[closeVertices[b]];
+            smoothBitangent += meshBitang[closeVertices[b]];
+        }
+        smoothTangent.Normalize();
+        smoothBitangent.Normalize();
+
+        // and write it back into all affected tangents
+        for (unsigned int b = 0; b < closeVertices.size(); ++b) {
+            meshTang[closeVertices[b]] = smoothTangent;
+            meshBitang[closeVertices[b]] = smoothBitangent;
+        }
+    }
+    return true;
+}