Fix [#26037] Import Collada crashes Blender

Submitted by David Roy

Multiple nodes can reference the same geometry, and specify the same materials. This lead
to the import code overwriting material mappings of faces in a destructive way. Instead of
just writing the material bindings always we now keep book of what geometry+material mapping
we've already handled.

2 files changed, 13 insertions, 0 deletions

diff --git a/source/blender/collada/MeshImporter.cpp b/source/blender/collada/MeshImporter.cpp
index 86dc1a44671..b6576858c51 100644
--- a/source/blender/collada/MeshImporter.cpp
+++ b/source/blender/collada/MeshImporter.cpp
@@ -803,6 +803,18 @@ MTFace *MeshImporter::assign_material_to_geom(COLLADAFW::MaterialBinding cmateri
 		return NULL;
 	}
 	
+	// different nodes can point to same geometry, but still also specify the same materials
+	// again. Make sure we don't overwrite them on the next occurrences, so keep list of
+	// what we already have handled.
+	std::multimap<COLLADAFW::UniqueId, COLLADAFW::UniqueId>::iterator it;
+	it=materials_mapped_to_geom.find(*geom_uid);
+	while(it!=materials_mapped_to_geom.end()) {
+		if(it->second == ma_uid) return NULL; // do nothing if already found
+		it++;
+	}
+	// first time we get geom_uid, ma_uid pair. Save for later check.
+	materials_mapped_to_geom.insert(std::pair<COLLADAFW::UniqueId, COLLADAFW::UniqueId>(*geom_uid, ma_uid));
+	
 	Material *ma = uid_material_map[ma_uid];
 	assign_material(ob, ma, ob->totcol + 1);
 	
diff --git a/source/blender/collada/MeshImporter.h b/source/blender/collada/MeshImporter.h
index 1a9f698a7ce..20fdb0dcc6e 100644
--- a/source/blender/collada/MeshImporter.h
+++ b/source/blender/collada/MeshImporter.h
@@ -91,6 +91,7 @@ private:
 	};
 	typedef std::map<COLLADAFW::MaterialId, std::vector<Primitive> > MaterialIdPrimitiveArrayMap;
 	std::map<COLLADAFW::UniqueId, MaterialIdPrimitiveArrayMap> geom_uid_mat_mapping_map; // crazy name!
+	std::multimap<COLLADAFW::UniqueId, COLLADAFW::UniqueId> materials_mapped_to_geom; //< materials that have already been mapped to a geometry. A pair of geom uid and mat uid, one geometry can have several materials
 	
 
 	void set_face_indices(MFace *mface, unsigned int *indices, bool quad);