If you load an alembic using vrayproxy, in a lot of cases vrayproxy is shifting some (not all) of the ids.
I could see this in most alembic exports from speedtree. But apparently this was a known issue (or feature?) where vrayproxy will rearange some ids from alembics, for some reason. This is pretty bad, and should be fixed.
Mind if you attach (or send) a sample alembic and some screencaps of the comparison?
I’ve used speedtree extensively over the years without issue, but also without passing through an ABC file.
So in my case it was ST to Obj, into Max, and then to proxy.
EDIT: I just tried the ABC export from v10, it naively looks like the ABC mtlIDs and sets are imported right, and the ABC set manager allows for the reordering.
What are the exact steps to reproduce the issue you’re having?
Sorry guys, my bad. Preparing an example to send, I figure out that the problem comes from speedtree. Its inconsistent how it writes material id data, and it changes id if you export as fbx or as alembic. At least with this examples, vrayproxy reads consistently IDs from alembics.
No worries, glad you sorted it.
Keep us posted if anything else suspicious comes up!