diff --git a/code/AssetLib/glTF2/glTF2Asset.h b/code/AssetLib/glTF2/glTF2Asset.h index 37aacd2fb..85eff4ac8 100644 --- a/code/AssetLib/glTF2/glTF2Asset.h +++ b/code/AssetLib/glTF2/glTF2Asset.h @@ -813,6 +813,11 @@ struct Mesh : public Object { AccessorList position, normal, tangent; }; std::vector targets; + + // extension: FB_ngon_encoding + bool ngonEncoded; + + Primitive(): ngonEncoded(false) {} }; std::vector primitives; diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.inl b/code/AssetLib/glTF2/glTF2AssetWriter.inl index aae96d0f7..01a28d4b7 100644 --- a/code/AssetLib/glTF2/glTF2AssetWriter.inl +++ b/code/AssetLib/glTF2/glTF2AssetWriter.inl @@ -509,6 +509,7 @@ namespace glTF2 { prim.SetObject(); // Extensions + if (p.ngonEncoded) { Value exts; exts.SetObject(); diff --git a/code/AssetLib/glTF2/glTF2Exporter.cpp b/code/AssetLib/glTF2/glTF2Exporter.cpp index d244e19f5..51aef013d 100644 --- a/code/AssetLib/glTF2/glTF2Exporter.cpp +++ b/code/AssetLib/glTF2/glTF2Exporter.cpp @@ -958,6 +958,7 @@ void glTF2Exporter::ExportMeshes() m->name = name; p.material = mAsset->materials.Get(aim->mMaterialIndex); + p.ngonEncoded = (aim->mPrimitiveTypes & aiPrimitiveType_NGONEncodingFlag) != 0; /******************* Vertices ********************/ Ref v = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mVertices, AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT, BufferViewTarget_ARRAY_BUFFER); diff --git a/code/PostProcessing/TriangulateProcess.cpp b/code/PostProcessing/TriangulateProcess.cpp index 00a55e35d..c982d9292 100644 --- a/code/PostProcessing/TriangulateProcess.cpp +++ b/code/PostProcessing/TriangulateProcess.cpp @@ -195,6 +195,13 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh) const aiVector3D* verts = pMesh->mVertices; + // NGON encoding note: making sure that triangles are not recognized as false ngons. + // To do so, we make sure the first indice of the new emitted triangle is not the same as previous one. + unsigned int prev_first_indice = (unsigned int)-1; + + // The mesh becomes NGON encoded now, during the triangulation process. + pMesh->mPrimitiveTypes |= aiPrimitiveType_NGONEncodingFlag; + // use std::unique_ptr to avoid slow std::vector specialiations std::unique_ptr done(new bool[max_out]); for( unsigned int a = 0; a < pMesh->mNumFaces; a++) { @@ -214,24 +221,12 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh) aiFace* const last_face = curOut; - // ngon encoding: making sure that triangles are not recognized as false ngons. - // To do so, we make sure the first indice is not the same as previous triangle emitted. - unsigned int prev_first_indice = (unsigned int)-1; - if (curOut != out) prev_first_indice = (curOut - 1)->mIndices[0]; - // if it's a simple point,line or triangle: just copy it if( face.mNumIndices <= 3) { aiFace& nface = *curOut++; nface.mNumIndices = face.mNumIndices; nface.mIndices = face.mIndices; - - if (nface.mIndices[0] == prev_first_indice) { - // rotate indices to avoid ngon encoding false ngons - std::swap(nface.mIndices[0], nface.mIndices[2]); - std::swap(nface.mIndices[1], nface.mIndices[2]); - } - face.mIndices = nullptr; continue; } @@ -242,7 +237,7 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh) // this vertex (if it exists) and start tri-fanning from // it. // - // Due to ngon encoding, if this concave vertex is the same as the previously + // Due to NGON encoding, if this concave vertex is the same as the previously // emitted triangle, we use the opposite vertex which also happens to work // for tri-fanning a concave quad. // ref: https://github.com/assimp/assimp/pull/3695#issuecomment-805999760 @@ -265,7 +260,7 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh) const float angle = std::acos(left*diag) + std::acos(right*diag); if (angle > AI_MATH_PI_F) { - // i is the concave point + // this is the concave point start_vertex = i; break; } @@ -306,11 +301,11 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh) // modeling suite to make extensive use of highly concave, monster polygons ... // so we need to apply the full 'ear cutting' algorithm to get it right. - // RERQUIREMENT: polygon is expected to be simple and *nearly* planar. + // REQUIREMENT: polygon is expected to be simple and *nearly* planar. // We project it onto a plane to get a 2d triangle. // Collect all vertices of of the polygon. - for (tmp = 0; tmp < max; ++tmp) { + for (tmp = 0; tmp < max; ++tmp) { temp_verts3d[tmp] = verts[idx[tmp]]; } @@ -530,6 +525,17 @@ bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh) i[0] = idx[i[0]]; i[1] = idx[i[1]]; i[2] = idx[i[2]]; + + // NGON encoding: only quads are supported. + // For everything else, we make sure we don't emit 'false' ngons. We thus avoid having + // 2 consecutive triangles with their first index identical. + if (face.mNumIndices != 4 && i[0] == prev_first_indice) { + // rotate indices + std::swap(i[0], i[2]); + std::swap(i[1], i[2]); + } + + prev_first_indice = i[0]; ++f; } diff --git a/include/assimp/mesh.h b/include/assimp/mesh.h index 8f17f541d..95651bd17 100644 --- a/include/assimp/mesh.h +++ b/include/assimp/mesh.h @@ -398,6 +398,24 @@ enum aiPrimitiveType { */ aiPrimitiveType_POLYGON = 0x8, + /** + * A flag to determine whether this triangles only mesh is NGON encoded. + * + * NGON encoding is a special encoding that tells whether 2 or more consecutive triangles + * should be considered as a triangle fan. This is identified by looking at the first vertex index. + * 2 consecutive triangles with the same 1st vertex index are part of the same + * NGON. + * + * At the moment, only quads (concave or convex) are supported, meaning that polygons are 'seen' as + * triangles, as usual after a triangulation pass. + * + * To get an NGON encoded mesh, please use the aiProcess_Triangulate post process. + * + * @see aiProcess_Triangulate + * @link https://github.com/KhronosGroup/glTF/pull/1620 + */ + aiPrimitiveType_NGONEncodingFlag = 0x16, + /** This value is not used. It is just here to force the * compiler to map this enum to a 32 Bit integer. */