Fix gltf static mesh loading issues (minetest#14)

* Support u8 / u32 indices

* Skip primitives without vertices

* Add support for non-indexed geometry & skipping primitives

* Fix possible memory leak on error

* Use SSkinnedMesh

* Check indices

* Properly mirror node hierarchy

* Update .gitignore

* Reorder includes

* Add some throws for logic errors

* Fix non-indexed geometry winding order, add unit test

* Address code review comments

* Add matrix transform unit test

.gitignore

@@ -23,3 +23,15 @@ scripts/glext.h
 
 # vscode cmake plugin
 build/*
+
+# vscode clangd plugin
+.cache
+compile_commands.json
+
+# build dependencies
+_deps
+
+# autogenerated test-related files
+**/CTestTestfile.cmake
+Testing
+DartConfiguration.tcl

include/SSkinMeshBuffer.h

@@ -301,7 +301,31 @@ struct SSkinMeshBuffer : public IMeshBuffer
 	}
 
 	//! append the vertices and indices to the current buffer
-	void append(const void *const vertices, u32 numVertices, const u16 *const indices, u32 numIndices) override {}
+	void append(const void* const vertices, u32 numVertices, const u16* const indices, u32 numIndices) override {
+		if (vertices == getVertices())
+			throw std::logic_error("can't append own vertices");
+
+		if (VertexType != video::EVT_STANDARD)
+			throw std::logic_error("invalid vertex type");
+
+		const u32 prevVertexCount = getVertexCount();
+
+		Vertices_Standard.reallocate(prevVertexCount + numVertices);
+		for (u32 i=0; i < numVertices; ++i) {
+			Vertices_Standard.push_back(static_cast<const video::S3DVertex* const>(vertices)[i]);
+			BoundingBox.addInternalPoint(static_cast<const video::S3DVertex* const>(vertices)[i].Pos);
+		}
+
+		Indices.reallocate(getIndexCount() + numIndices);
+		for (u32 i=0; i < numIndices; ++i) {
+			Indices.push_back(indices[i] + prevVertexCount);
+		}
+	}
+
+	//! NOT IMPLEMENTED YET: append the meshbuffer to the current buffer
+	void append(const IMeshBuffer* const other) override {
+		throw std::logic_error("not implemented yet");
+	}
 
 	//! get the current hardware mapping hint for vertex buffers
 	E_HARDWARE_MAPPING getHardwareMappingHint_Vertex() const override