Hey guys!

I'm using packed geo to procedurally animate transforms within the SOP context.
(think packed geo coming out of a dopimport node, or wrangling the packed intrinsic attributes)

When I export this to alembic with the “packed geometry” option set to “transform geometry”, I get static meshes with animated xforms - as expected.

However, sometimes the exported alembic file contains deforming meshes, with miniscule (0.00001) deltas on the point positions.
This is what I see in HDFview, when converting the file with abcconvert:


Our pipeline behaves different when alembic considers a mesh as homogeneous, as opposed to constant.
Is there a way to get rid of this error?

Maybe one of the SideFX guys here can shed some light on what happens behind the scenes, when alembic exports packed geometry?
I'd love to understand how exactly houdini figures out whether packed geometry is static, or not.

Cheers!
-Sascha

I found the culprit!
Turns out that the blendshape node, I use to conveniently blend packed animations, modifies the packed geo!

If I add a wrangle afterwards, to copy the packed transform onto the unblended geo, it exports as undeforming:


Now - anybody out there who knows how exactly the blendshape node handles packed geo?