Combine and separate objects to improve frame rate

Large production models, which typically have hundreds of parts that are comprised of thousands of surfaces and surface patches, can significantly slow Hardware rendering performance (the frame rate) while interactively authoring or presenting a scene.

You can improve the interaction performance (even with multiple production models loaded and displayed side by side) by combining objects in the Organizer. Combining objects essentially flattens the selected object hierarchy to speed the frame rate. However, to prevent data loss (for example, material assignments), you must follow the workflow guidelines and possibly modify your workflow.

Follow these working guidelines to combine nodes successfully without losing important data:

• Resist combining objects that go into different alternatives or behaviors. If you do combine the objects, the assignments may break, and you may need to redo the reassignments.
• Precalculated ambient shadows may be adversely affected when you combine mixed geometry (for example, polys and NURBS). Before combining, occlusion is applied differently to different data types (for NURBS, through textures; for polys, through vertex colors); after combining, NURBS and polys textures are ignored, and all occlusion is vertex based.
• Combining a shadow caster will result in the entire combined node being a shadow caster for that light.
• Combining objects that may appear to have the same texture may cause the texture placement to shift or scale in unexpected ways. In this case, re-place the texture on the combined object.
• You cannot combine a node that has already combined objects within it; the combine button and menu item is not available in this case. An alternative approach is to separate the combined node, then combine at a higher level of the hierarchy.
• Combining should be done only if you are sure that nothing else is going to change in the geometry. If you combine and then decide to update or re-tessellate your model because of changes done in the originating application, you may encounter geometry issues.
• When combining multiple objects with different materials, the first material found is applied to all. For example:
  • Object A is combined with Material A
  • Object B is combined with Material B

  If you combine those two objects, you get:

  • Object C With Material A
• If you plan to animate objects, keep the objects separate.

To combine objects:

1. In the Organizer, select the objects you want to combine, then group them. The objects are grouped into one folder.
   
2. Right-click the folder with the grouped objects, and select Combine. The objects are combined and you can no longer expand the node to see its contents.
   
   Note

   Double-click the folder to folder to give it a more meaningful name.

   

You can separate combined objects to gain access to parts of the combined geometry to work with it (for example, to flip normals, to remove duplicate surface, or to split geometry to add different alternatives or behaviors).

Separating is not the same as undoing (Edit > Undo) the combination operation. Separating retains the object hierarchy but gives you access to combined objects; undoing reverts to the original object hierarchies within a scene session.

To separate objects:

1. In the Organizer, select the combined objects you want to separate.
2. Right-click the selected objects, and choose Separate. The objects are separated, and you can now expand the node to see its contents.