Sybren A. Stüvel
a1c9d42584
This was caused by a side-effect of our exporting code's memory management (Alembic considers data "written" and "final" when its C++ objects go out of scope) in combination with my change in rB65574463fa2d. I removed an "only export UVs on the first frame" clause because it was unclear why this restriction was there. As it turns out, it breaks the export of the 2nd and subsequent UV maps on an animated mesh. Effectively, on every frame the Alembic library thought we want to create a new UV map, instead of continuing to write a new frame of data to the existing one. This is resolved by keeping a reference to the C++ objects for the UV maps in memory while the exporter is running.