UsdPreviewSurface spec change: UsdPrimvarReader.varname type (token -> string)

Community USD
1

While updating our exporter to the latest changes in the UsdPreviewSurface spec, I noticed that the proposed type change for UsdPrimvarReader.varname (token → string) is not working in Houdini 20.5, nor the latest Omniverse Composer, nor UsdView 24.3 itself.

Surprisingly, Houdini 20.5 writes varname as a string type (at least to usda) but then cannot read it back in correctly.

Does this mean that UsdPreviewSurface > 2.2 is not yet recommended for use in practice?

Thanks & kind regards,
Simon

2

Hi @shaegler , AFAICT from a quick code/test inspection (not comprehensive), we are specifying and consuming varname as a string. Can you please file an Issue with a small repro?

Thanks!

3

Thanks for the confirmation @spiff.

I tested again and now I can only reproduce the problem with Houdini (20.5). Not sure why I mixed up these results…

So, UsdView and Omniverse Composer work with varname either as string or token (though the latter has a reload/cache bug if I modify the type of varname and use the builtin stage reload mechanism).

Will followup with SideFX support separately…

Thanks & best,
Simon

4

Need to talk to myself here - all good with Houdini. My test setup had a subtle flaw (the classic reference layer vs sublayer thing). Also, note to myself, always check the return value of attr “.Set” to spot type mismatches.

All good.