message: If OBJ model provides no materials, create a default to use
  otherwise it uses the last material on the registry list
diff: @@ -298,6 +298,9 @@ namespace ospray {
  auto objData = loadFromFile(fileName);
  auto materialNodes = createMaterials(objData, fileName);
  + // If the model provided no materials, create a default
  + if (materialNodes.empty())
  + materialNodes.emplace_back(createNode("default", "obj"));
  size_t baseMaterialOffset = materialRegistry->children().size();
  