Hi guys,

In some Solaris tutorial I saw, when someone created a simulation from a already extant prim/mesh in Solaris, that he just ‘pruned’ that original object (object/objectGeo)/made it invisible, and put the simulated geometry in another prim (object/objectSimulatedGeo) which was visible.

I imagine that in some cases it would be more memory-efficient to just replace the ‘objectGeo’ with the ‘objectSimulatedGeo’, so that you only have the simulated geometry. Does this trespass the warning, that you hear often, that you should not delete prims in USD?

In either of these cases the connections with the primvars of the object/objectGeo/mesh are lost, right?


Also: another take, or brainstorm, on this ‘replacement’ issue:
In this old deprecated pixar tutorial [graphics.pixar.com] you see, in the section ‘Overlays’, that an old Houdini node has options to overwrite Transforms, Points, Primvars and All.

When in that tutorial he replaces source-geo with ‘sim-geo’, he must choose ‘All’, which breaks the connections with the other primvars of the original mesh.
I wonder: is it nowadays possible to just overwrite topology primvar, and ‘replace’ the geo that way, and keep all other connections. Would this be the best workflow, if possible?

Thanks for the help,

OdFotan
I imagine that in some cases it would be more memory-efficient to just replace the ‘objectGeo’ with the ‘objectSimulatedGeo’, so that you only have the simulated geometry. Does this trespass the warning, that you hear often, that you should not delete prims in USD?

Not should, but can't. There is no delete in USD. The simulated mesh could overlay the original mesh. However, if the topology is different, you have to be sure to express an opinion on all the mesh's primvars that are non-constant as the new topology won't map to the underlying mesh's primvars correctly anymore. Constant primvars (detail attributes in houdini speak) can be carried from pre sim geo, and any parent prims primvars.

OdFotan
In either of these cases the connections with the primvars of the object/objectGeo/mesh are lost, right?

Correct a new mesh in a new prim spec will have no relation to the original, inheritance-wise. This can be a good thing though, as when topology changes, attributes that vary per vertex or face will be unusable anyway.

I believe sidefx have some FX layering examples in the docs.

It would probably be more scalable and flexible if you rather author a new variant containing a reference to your sim-geo than try to overlay/rehabilitate your source geo.

In USD, Variants are very efficient to read, you can author a ton of variants and not feel the impact upon read.

Hi Jason. That is a great tip. I have been using opinion strength as it never occurred to me to alter it with variant instead. Best

I think it would be nice to have an example of both
But I have problems with exporting deformed geometry from SOP.
Any help would be appreciated!
Thanks