Alembic cache import issue - missing one frame

Development Character & Animation
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1

I found an issue with the Alembic geo cache.
I did all the animation in Maya, and exported as Alembic cache files. But when importing to Unreal, one frame will be missing. For example, one shot in Maya is from frame 1-40, but when it is in Unreal will be from 1-39.

I think this issue is caused by the different timeline settings between Maya and Unreal.
In Maya, set the time to end at frame 40, and frame 40 is included in the timeline. But this is not the case in Unreal. When I set the playback end at frame 40 in Unreal, it will actually end at frame 39.
I can manually set one frame longer for the timeline indeed, but the issue is geometry cache works just like the timeline - the cache will end at frame 39 too. If I manually longer one frame, it’ll look good in the viewport, but the rendered frame 40 will be affected by motion blur, becoming blurry and transparent.

FBX files don’t have this issue, only ABC files do. FBX animation works perfectly.

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Hey @NanL, this is actually a pretty common off-by-one quirk when you bring an Alembic cache into Unreal. Maya treats your frame range as inclusive so if you bake 1–40, you really get frame 40, whereas Unreal’s Geometry Cache importer treats the end frame as exclusive (so telling it to import 1–40 really gives you 1–39). FBX animations don’t hit this snag because Unreal maps their duration differently and always includes the last frame.

To work around it, you’ve got two easy options: either export one extra frame from Maya (so bake 1–41) and keep Unreal’s import at 1–40, or manually set the Unreal import range to 1–41 (so you grab everything up to but not including frame 41). Either way, your “frame 40” data lands where you expect it.

I know this reply is coming very late but hopefully someone else could make a use of it..