Why does UsdImagingSelectionSceneIndex::GetPrim() add a selection data source to all prims?

Community Hydra
1

seems to add a selection data source to all (valid) scene index prims. Why is that? My expectation would be that only selected scene index prims would need this. Thanks for any help.

Pierre

2

Hi Pierre,

The selection scene index will perform a map on every prim, but the map is evaluated (and potentially re-evaluated) lazily, and refers to the selection state. If you look up a bit: https://github.com/PixarAnimationStudios/OpenUSD/blob/0b18ad3f840c24eb25e16b795a5b0821cf05126e/pxr/usdImaging/usdImaging/selectionSceneIndex.cpp#L191 … in _PrimSource, you can see that if the prim is selected, we overlay a “selections” datasource onto it; and if not, we just pass through to the underlying scene data.

Hope that clarifies!
Tom