message: flatten .obj shapes (no instancing), better performance for demos
  NOTE: this should be configurable in the future (note added accordingly)
diff: @@ -260,11 +260,19 @@ namespace ospray {
  auto model = createNode(name + "_model", "Model");
  model->add(mesh);
  + // TODO: Large .obj models with lots of groups run much slower with each
  + // group put in a separate instance. In the future, we want to
  + // support letting the user (ospExampleViewer, for starters)
  + // specify if each group should be placed in an instance or not.
  +#if 0
  auto instance = createNode(name + "_instance", "Instance");
  instance->setChild("model", model);
  model->setParent(instance);
  world->add(instance);
  +#else
  + world->add(mesh);
  +#endif
  }
  }
  