I have an alembic of some splashing water. I'd like to use it in slow motion, 20% speed. Is there any way to do that? I believe alembics have no concept of frames, which seems like it should mean it's easy to get them to interpret at a different rate. But I don't see any way to get an alembic that lasts x number of frames to play over x*5 frames.
Yes, I've just needed to do the same... Turn on and keyframe "Override Frame" value in MeshSechuenceCache modifier where are the alembic data options. First keframe 0 - on frame 0 and second keyframe 100 on frame 100(if you alembic has 100 frames). Then go to graph editor and turn of "Only show selected" tick on the righ top panel. Find your custom alembic curve and adjust it how ever you need.
Just a little more clarification to this process.
The Override Frame feature is basically allowing you to adjust how many frames from the alembic file will play over time. By default, ticked off, it means the file will play as recorded from the start to the end. For example from frame 0 to 100.
Override Frame means you can now set this manually. So if you set keys at 0 and 100 and at the keyframe of 100 you set the value of 100, this means it will play in the normal time.
However if at frame 100 you set a value of 50. This means it will take 100 frames to reach 50 frames of the alembic animation. So this would be 1/2 speed.
So this also means that the animation will stop at 50 frames on frame 100, if you have more frames than 100. And you can speed up as well as slow down the animation with the same method by entering a value higher value, for example 200 at frame 100 to play it 2X as fast from frame 0 to 100. But for this to work, you would need to have 200 or more frames in the Alembic file. Otherwise it will stop playing at frame 50 if you only have 100 frames.