tried to add assimp (spoilers, it did not go well, so hey! now we have separate fiels now.)

src/ThirdParty/assimp/code/AssetLib/Blender/BlenderBMesh.cpp

@@ -0,0 +1,185 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2025, 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  BlenderBMesh.cpp
+ *  @brief Conversion of Blender's new BMesh stuff
+ */
+
+#ifndef ASSIMP_BUILD_NO_BLEND_IMPORTER
+
+#include "BlenderBMesh.h"
+#include "BlenderDNA.h"
+#include "BlenderScene.h"
+#include "BlenderTessellator.h"
+
+namespace Assimp {
+template <>
+const char *LogFunctions<BlenderBMeshConverter>::Prefix() {
+    return "BLEND_BMESH: ";
+}
+} // namespace Assimp
+
+using namespace Assimp;
+using namespace Assimp::Blender;
+using namespace Assimp::Formatter;
+
+// ------------------------------------------------------------------------------------------------
+BlenderBMeshConverter::BlenderBMeshConverter(const Mesh *mesh) :
+        BMesh(mesh),
+        triMesh(nullptr) {
+    ai_assert(nullptr != mesh);
+}
+
+// ------------------------------------------------------------------------------------------------
+BlenderBMeshConverter::~BlenderBMeshConverter() {
+    DestroyTriMesh();
+}
+
+// ------------------------------------------------------------------------------------------------
+bool BlenderBMeshConverter::ContainsBMesh() const {
+    if (BMesh == nullptr) {
+        return false;
+    }
+    return BMesh->totpoly && BMesh->totloop && BMesh->totvert;
+}
+
+// ------------------------------------------------------------------------------------------------
+const Mesh *BlenderBMeshConverter::TriangulateBMesh() {
+    AssertValidMesh();
+    AssertValidSizes();
+    PrepareTriMesh();
+
+    for (int i = 0; i < BMesh->totpoly; ++i) {
+        const MPoly &poly = BMesh->mpoly[i];
+        ConvertPolyToFaces(poly);
+    }
+
+    return triMesh;
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::AssertValidMesh() {
+    if (!ContainsBMesh()) {
+        ThrowException("BlenderBMeshConverter requires a BMesh with \"polygons\" - please call BlenderBMeshConverter::ContainsBMesh to check this first");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::AssertValidSizes() {
+    if (BMesh->totpoly != static_cast<int>(BMesh->mpoly.size())) {
+        ThrowException("BMesh poly array has incorrect size");
+    }
+    if (BMesh->totloop != static_cast<int>(BMesh->mloop.size())) {
+        ThrowException("BMesh loop array has incorrect size");
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::PrepareTriMesh() {
+    if (triMesh) {
+        DestroyTriMesh();
+    }
+
+    triMesh = new Mesh(*BMesh);
+    triMesh->totface = 0;
+    triMesh->mface.clear();
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::DestroyTriMesh() {
+    delete triMesh;
+    triMesh = nullptr;
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::ConvertPolyToFaces(const MPoly &poly) {
+    const MLoop *polyLoop = &BMesh->mloop[poly.loopstart];
+
+    if (poly.totloop == 3 || poly.totloop == 4) {
+        AddFace(polyLoop[0].v, polyLoop[1].v, polyLoop[2].v, poly.totloop == 4 ? polyLoop[3].v : 0);
+
+        // UVs are optional, so only convert when present.
+        if (BMesh->mloopuv.size()) {
+            if ((poly.loopstart + poly.totloop) > static_cast<int>(BMesh->mloopuv.size())) {
+                ThrowException("BMesh uv loop array has incorrect size");
+            }
+            const MLoopUV *loopUV = &BMesh->mloopuv[poly.loopstart];
+            AddTFace(loopUV[0].uv, loopUV[1].uv, loopUV[2].uv, poly.totloop == 4 ? loopUV[3].uv : nullptr);
+        }
+    } else if (poly.totloop > 4) {
+#if ASSIMP_BLEND_WITH_GLU_TESSELLATE
+        BlenderTessellatorGL tessGL(*this);
+        tessGL.Tessellate(polyLoop, poly.totloop, triMesh->mvert);
+#elif ASSIMP_BLEND_WITH_POLY_2_TRI
+        BlenderTessellatorP2T tessP2T(*this);
+        tessP2T.Tessellate(polyLoop, poly.totloop, triMesh->mvert);
+#endif
+    }
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::AddFace(int v1, int v2, int v3, int v4) {
+    MFace face;
+    face.v1 = v1;
+    face.v2 = v2;
+    face.v3 = v3;
+    face.v4 = v4;
+    face.flag = 0;
+    // TODO - Work out how materials work
+    face.mat_nr = 0;
+    triMesh->mface.push_back(face);
+    triMesh->totface = static_cast<int>(triMesh->mface.size());
+}
+
+// ------------------------------------------------------------------------------------------------
+void BlenderBMeshConverter::AddTFace(const float *uv1, const float *uv2, const float *uv3, const float *uv4) {
+    MTFace mtface;
+    memcpy(&mtface.uv[0], uv1, sizeof(float) * 2);
+    memcpy(&mtface.uv[1], uv2, sizeof(float) * 2);
+    memcpy(&mtface.uv[2], uv3, sizeof(float) * 2);
+
+    if (uv4) {
+        memcpy(&mtface.uv[3], uv4, sizeof(float) * 2);
+    }
+
+    triMesh->mtface.push_back(mtface);
+}
+
+#endif // ASSIMP_BUILD_NO_BLEND_IMPORTER