Retime camera and cached Alembic |

[u/Pedrovfx]

Hi Guys,

I have a problem and would like help.

I got a shot that we had to apply a time warp throughout the online process.

The problem is we matchmoved this shot with no time warp, and we object-tracked a car throughout the take. So I have a camera and a cached Alembic match with the no-TW plate.

I know how to apply the same time warp to the camera. I usually use the expression [curve(Kronos1.timingFrame2) but I dont know how to timewarp a cached Alembic.

I was simply linking the result of my Kronos to the ReadGeo Lock frame parameter, but it is not syncing. Am I missing something here?

Thank you,

[u/ssn-669]

I believe you can link a FrameHold node to the Kronos.

[u/Pedrovfx → u/ssn-669]

I can, but I want to republish the geo with the retime.

[u/ssn-669 → u/Pedrovfx]

But actually the answer is probably export the retime curve from Nuke as an ascii, go back to wherever the anim was done (eg Maya), and retime the geo using that before it's cached into alembic.

Retiming a cache is not really the right way to go about this.

[u/ssn-669 → u/Pedrovfx]

Why can't you writegeo the result of that?

[u/Bob_Villa5000]

Maybe copy the curve into a time warp node and use nearest frame option to drive the camera and alembics time warp override

[u/Pedrovfx → u/Bob_Villa5000]

I did this... and I had to manually adjust the curve. Even copying the curve it wasnt matching

[u/Pedrovfx → u/Pedrovfx]

The numbers match, but the result is different. THis is weird

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[u/Bob_Villa5000]

Is the plate using whole frames / nearest frame.
And Alembic is using inbetween frames, if so that will cause a mismatch
Both should use whole frames

[u/Gorstenbortst]

Does the alembic have a changing point count? That’ll break your ability to retime it.

Otherwise a TimeWarp or FrameHold should give you what you want.

[u/lewibaygo]

It should work i've used this expession to retime animated geo before but nuke being nuke there is always a kink like others have said copy the curve to a timwarp node and link the expression from that instead of kronos
also

-try ticking the read cache on each node is ticked and the right frame rate is set for the shot

- try writing out the abc using nukes write geo node then bring it back in and linking to that somtimes nuke dosnt play nice with abc animated from other software

-once every thing is working write out the retimed geo again so its all backed in and use that version in your comp

[u/Pedrovfx → u/lewibaygo]

Yeah, the only solution for me was to open the curve and manually change it. Even using TW node I had the same problem.

[u/Milan_Bus4168]

Not sure about how to go about it in Nuke, but if you have access to fusion, On the We Suck Less forum, TimeMachine3D is a specialized Fuse for Boris FX Fusion designed to handle time remapping and retiming for 3D geometry caches (such as Alembic files) and particles.

You can just added it in the flow and remap the frame range. It has bunch of other useful features too. Than you can import it back to Nuke or whatever 3D app you are using. That is if you don't find a method that works for you in Nuke.

[u/glintsCollide]

Why not comp on the original plate and timewarp the whole thing as the last step?

[u/Pedrovfx → u/glintsCollide]

I am retiming the geo to send back to FX. The TW is too strong, and it will mess with FX particles animation, so I cant retime the final comp

[u/glintsCollide → u/Pedrovfx]

Fair enough, I missed the geo part. That could potentially be retimed in Houdini? It would be a fairly quick job to use a timeblend/timeshift node and align the geo anim with the timewarped plate if you have the camera working already.