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.

1 files changed, 12 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);