Merge pull request #3695 from AllegorithmicSAS/feature/gltf_fb_ngon_encoding
[gltf2-exporter] Adding FB_ngon_encoding supportpull/3749/head^2
Kim Kulling
GitHub
commit
6eae925441
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@ -813,6 +813,11 @@ struct Mesh : public Object {
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AccessorList position, normal, tangent;
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};
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std::vector<Target> targets;
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// extension: FB_ngon_encoding
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bool ngonEncoded;
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Primitive(): ngonEncoded(false) {}
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};
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std::vector<Primitive> primitives;
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@ -1108,6 +1113,7 @@ public:
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bool KHR_materials_clearcoat;
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bool KHR_materials_transmission;
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bool KHR_draco_mesh_compression;
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bool FB_ngon_encoding;
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} extensionsUsed;
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//! Keeps info about the required extensions
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@ -507,6 +507,20 @@ namespace glTF2 {
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Mesh::Primitive& p = m.primitives[i];
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Value prim;
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prim.SetObject();
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// Extensions
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if (p.ngonEncoded)
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{
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Value exts;
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exts.SetObject();
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Value FB_ngon_encoding;
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FB_ngon_encoding.SetObject();
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exts.AddMember(StringRef("FB_ngon_encoding"), FB_ngon_encoding, w.mAl);
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prim.AddMember("extensions", exts, w.mAl);
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}
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{
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prim.AddMember("mode", Value(int(p.mode)).Move(), w.mAl);
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@ -874,6 +888,10 @@ namespace glTF2 {
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if (this->mAsset.extensionsUsed.KHR_materials_transmission) {
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exts.PushBack(StringRef("KHR_materials_transmission"), mAl);
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}
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if (this->mAsset.extensionsUsed.FB_ngon_encoding) {
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exts.PushBack(StringRef("FB_ngon_encoding"), mAl);
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}
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}
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if (!exts.Empty())
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@ -97,6 +97,9 @@ glTF2Exporter::glTF2Exporter(const char* filename, IOSystem* pIOSystem, const ai
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mAsset.reset( new Asset( pIOSystem ) );
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// Always on as our triangulation process is aware of this type of encoding
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mAsset->extensionsUsed.FB_ngon_encoding = true;
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if (isBinary) {
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mAsset->SetAsBinary();
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}
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@ -955,6 +958,7 @@ void glTF2Exporter::ExportMeshes()
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m->name = name;
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p.material = mAsset->materials.Get(aim->mMaterialIndex);
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p.ngonEncoded = (aim->mPrimitiveTypes & aiPrimitiveType_NGONEncodingFlag) != 0;
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/******************* Vertices ********************/
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Ref<Accessor> v = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mVertices, AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT, BufferViewTarget_ARRAY_BUFFER);
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@ -76,6 +76,87 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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using namespace Assimp;
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namespace {
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/**
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* @brief Helper struct used to simplify NGON encoding functions.
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*/
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struct NGONEncoder {
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NGONEncoder() : mLastNGONFirstIndex((unsigned int)-1) {}
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/**
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* @brief Encode the current triangle, and make sure it is recognized as a triangle.
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*
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* This method will rotate indices in tri if needed in order to avoid tri to be considered
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* part of the previous ngon. This method is to be used whenever you want to emit a real triangle,
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* and make sure it is seen as a triangle.
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*
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* @param tri Triangle to encode.
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*/
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void ngonEncodeTriangle(aiFace * tri) {
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ai_assert(tri->mNumIndices == 3);
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// Rotate indices in new triangle to avoid ngon encoding false ngons
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// Otherwise, the new triangle would be considered part of the previous NGON.
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if (isConsideredSameAsLastNgon(tri)) {
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std::swap(tri->mIndices[0], tri->mIndices[2]);
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std::swap(tri->mIndices[1], tri->mIndices[2]);
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}
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mLastNGONFirstIndex = tri->mIndices[0];
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}
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/**
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* @brief Encode a quad (2 triangles) in ngon encoding, and make sure they are seen as a single ngon.
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*
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* @param tri1 First quad triangle
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* @param tri2 Second quad triangle
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*
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* @pre Triangles must be properly fanned from the most appropriate vertex.
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*/
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void ngonEncodeQuad(aiFace *tri1, aiFace *tri2) {
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ai_assert(tri1->mNumIndices == 3);
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ai_assert(tri2->mNumIndices == 3);
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ai_assert(tri1->mIndices[0] == tri2->mIndices[0]);
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// If the selected fanning vertex is the same as the previously
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// emitted ngon, we use the opposite vertex which also happens to work
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// for tri-fanning a concave quad.
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// ref: https://github.com/assimp/assimp/pull/3695#issuecomment-805999760
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if (isConsideredSameAsLastNgon(tri1)) {
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// Right-rotate indices for tri1 (index 2 becomes the new fanning vertex)
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std::swap(tri1->mIndices[0], tri1->mIndices[2]);
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std::swap(tri1->mIndices[1], tri1->mIndices[2]);
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// Left-rotate indices for tri2 (index 2 becomes the new fanning vertex)
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std::swap(tri2->mIndices[1], tri2->mIndices[2]);
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std::swap(tri2->mIndices[0], tri2->mIndices[2]);
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ai_assert(tri1->mIndices[0] == tri2->mIndices[0]);
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}
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mLastNGONFirstIndex = tri1->mIndices[0];
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}
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/**
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* @brief Check whether this triangle would be considered part of the lastly emitted ngon or not.
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*
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* @param tri Current triangle.
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* @return true If used as is, this triangle will be part of last ngon.
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* @return false If used as is, this triangle is not considered part of the last ngon.
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*/
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bool isConsideredSameAsLastNgon(const aiFace * tri) const {
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ai_assert(tri->mNumIndices == 3);
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return tri->mIndices[0] == mLastNGONFirstIndex;
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}
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private:
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unsigned int mLastNGONFirstIndex;
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};
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}
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// ------------------------------------------------------------------------------------------------
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// Constructor to be privately used by Importer
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TriangulateProcess::TriangulateProcess()
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@ -175,10 +256,15 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
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pMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
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pMesh->mPrimitiveTypes &= ~aiPrimitiveType_POLYGON;
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// The mesh becomes NGON encoded now, during the triangulation process.
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pMesh->mPrimitiveTypes |= aiPrimitiveType_NGONEncodingFlag;
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aiFace* out = new aiFace[numOut](), *curOut = out;
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std::vector<aiVector3D> temp_verts3d(max_out+2); /* temporary storage for vertices */
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std::vector<aiVector2D> temp_verts(max_out+2);
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NGONEncoder ngonEncoder;
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// Apply vertex colors to represent the face winding?
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#ifdef AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
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if (!pMesh->mColors[0])
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@ -220,8 +306,11 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
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aiFace& nface = *curOut++;
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nface.mNumIndices = face.mNumIndices;
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nface.mIndices = face.mIndices;
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face.mIndices = nullptr;
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// points and lines don't require ngon encoding (and are not supported either!)
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if (nface.mNumIndices == 3) ngonEncoder.ngonEncodeTriangle(&nface);
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continue;
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}
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// optimized code for quadrilaterals
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@ -274,6 +363,9 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
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// prevent double deletion of the indices field
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face.mIndices = nullptr;
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ngonEncoder.ngonEncodeQuad(&nface, &sface);
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continue;
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}
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else
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@ -284,7 +376,7 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
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// modeling suite to make extensive use of highly concave, monster polygons ...
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// so we need to apply the full 'ear cutting' algorithm to get it right.
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// RERQUIREMENT: polygon is expected to be simple and *nearly* planar.
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// REQUIREMENT: polygon is expected to be simple and *nearly* planar.
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// We project it onto a plane to get a 2d triangle.
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// Collect all vertices of of the polygon.
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@ -508,6 +600,11 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
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i[0] = idx[i[0]];
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i[1] = idx[i[1]];
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i[2] = idx[i[2]];
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// IMPROVEMENT: Polygons are not supported yet by this ngon encoding + triangulation step.
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// So we encode polygons as regular triangles. No way to reconstruct the original
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// polygon in this case.
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ngonEncoder.ngonEncodeTriangle(f);
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++f;
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}
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@ -398,6 +398,24 @@ enum aiPrimitiveType {
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*/
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aiPrimitiveType_POLYGON = 0x8,
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/**
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* A flag to determine whether this triangles only mesh is NGON encoded.
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*
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* NGON encoding is a special encoding that tells whether 2 or more consecutive triangles
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* should be considered as a triangle fan. This is identified by looking at the first vertex index.
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* 2 consecutive triangles with the same 1st vertex index are part of the same
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* NGON.
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*
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* At the moment, only quads (concave or convex) are supported, meaning that polygons are 'seen' as
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* triangles, as usual after a triangulation pass.
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*
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* To get an NGON encoded mesh, please use the aiProcess_Triangulate post process.
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*
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* @see aiProcess_Triangulate
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* @link https://github.com/KhronosGroup/glTF/pull/1620
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*/
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aiPrimitiveType_NGONEncodingFlag = 0x10,
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/** This value is not used. It is just here to force the
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* compiler to map this enum to a 32 Bit integer.
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*/
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