Strange Offset for an animated Alembic in the Proxy Node with Playback to Once

[seq]

Hi,

we have an animated Alembic file with 87 resolved frames. We want the animation to start at frame 1000. With the Playback type set to Once, the offset needs to be -1000 to get the animation starting at frame 1000. Why do we need to set a negative number?

TIA
Lars

[Joelaff]

It believe is tied in with the start frame in the application that created the ABC. It’s definitely not very straightforward.

[seq]

Thanks for the hint. The abc is exported from Houdini. Will ask my colleague to set the start frame to 1000.

[Joelaff]

Note, I am not sure that it directly coincides with the start frame in the file. It may have to do with a built in offset to get the start frame in the file to match the start frame in your DCC. But I really can't recall. There is no doubt it is always confusing, though.

Dunno about Maya, or if it has been fixed yet, but there was a bug (in Max at least) where if you ticked Use Alembic Offset the IPR would restart over and over with Building Light Cache. The workaround was to tick that box once, to set the value, and then untick it. If you do figure out the precise logic let us know

[seq]

Yeah, confusing nailed it down. Will report back when we find something useful in the abc-jungle.

[hermit.crab]

Hi,

we have an animated Alembic file with 87 resolved frames. We want the animation to start at frame 1000. With the Playback type set to Once, the offset needs to be -1000 to get the animation starting at frame 1000. Why do we need to set a negative number?

TIA
Lars

Are you referring to the fact that when using negative values you offset forwards, and when using positive values - backward? This is indeed a bit strange. I tested it by exporting a .abc from Maya and it works correctly, only the value behaviour is confusing.

[seq]

It's really confusing: We have one Alembic including an animation which was exported from Houdini with starting frame 1000. We want the animation in Maya to start also at frame 1000.

Maya -> frame 1000 / VRayProxy -> Once, Start offset 0 => last frame of the alembic animation is shown
Maya -> frame 1000 / VRayProxy -> Once, Start offset 1000 => last frame of the alembic animation is shown
Maya -> frame 1000 / VRayProxy -> Once, Start offset -1000 => first frame of the alembic animation is shown

With separate abc for each frame (also exported from Houdini with start frame 1000), we can load the sequence and leave the start offset at 0.

[hsz]

if you are using the same timeline meaning H and M start the sequence at frame 1001 or 1000 whatever, just check "use alembic animation offset" that's all that you should do.

[seq]

Damn how obvious. Thanks. Will now check how it behaves when the sequence start in the exporting software is 0 or 1 or whatever.

[Joelaff]

If your IPR starts getting stuck on Building Light Cache with use Alembic Offset see my note in post Groups about this option.

[hermit.crab]

seq I tested with a Houdini .abc and indeed the "Use alembic animation offset" yields correct results without any need for offset. Otherwise, I've logged an improvement request (internal tracker id: VMAYA-13392) to make the positive/negative values respectively offset the animation forwards/backwards (not the other way around).

[seq]

hermit.crab Yes, works here fine also. Thanks for the internal request.

Joelaff Thnks, but had no problem so far with LC.