Autodesk: Support float type matrix (GfMatrix4f) for instanceTransform

[erikaharrison-adsk]

Description of Change(s)

Support VtArray as the value type for token instanceTransform

A instancer may contain huge number of matrices and occupy lots of memory. Some data models only need float precision
matrices for instancers, however USD only accepts VtArray, doubling the memory size needed.
To save the memory, this fix allows USD to accept instancer matrices of type VtArray directly.

Fixes Issue(s)

• N/A

• I have verified that all unit tests pass with the proposed changes

• I have submitted a signed Contributor License Agreement

[jesschimein]

Filed as internal issue #USD-8762

[jesschimein]

Hi Erika! I'm also seeing this change in dev in instancer.cpp and in history. Let me know if you're still not seeing it?

…

On Fri, Dec 15, 2023 at 3:06 PM Erika Harrison ***@***.***> wrote: @jesschimein <https://github.com/jesschimein> - I notice this is marked as "merged" but I'm not seeing the changes in instancer.cpp nor its commit history. How does this work? Is there a delay? https://git.autodesk.com/autodesk-forks/USD/commits/dev/pxr/imaging/hdSt/instancer.cpp — Reply to this email directly, view it on GitHub <#2724 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ARL2WZP2BDP7VBY6GA4V3VLYJTJWZAVCNFSM6AAAAAA5LST2RKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQNJYGU4TCNRXGA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[wingfiring]

Hi @jesschimein,

I noticed that the following statements are removed from the merge commit

The original conditional expression in if and the else branch are

if ((primvar.name == HdInstancerTokens->instanceTransform ||
                 primvar.name == HdInstancerTokens->instanceTransforms) &&
                TF_VERIFY(value.IsHolding<VtArray<GfMatrix4d> >())) {
...
}
else {
                source.reset(new HdVtBufferSource(primvar.name, value));

if TF_VERIFY(value.IsHolding<VtArray<GfMatrix4d> >()) is false, the control flow will jump to else branch. In my PR, I moved the value.IsHolding into if branch, so I added the else branch as above to do the same thing as original. It doesn’t affect our current work, but it might affect extensibility (for example, set a non-matrix data and would be consumed by customized render delegate).
Could you please confirm that the change is intentional? Thanks a lot!