Alembic Instance topology data not found

[tobiasroesli]

Hi,

I can't figure out how to render an animated Alembic with changing topology and motion blur.

I gave the animated Alembic a "v" attribute with "0" and if I switch the Geometry Velocity Blur in the GEO settings to "Velocity Blur" it will render of course no motion blur.

But the transform blur is ignored because of the "Geometry Velocity Blur: Velocity Blur".
With "Geometry Velocity Blur: No Velocity Blur" I get the "Error : Instance topology data not found for instance"

it works all fine if I use no $F for the Alembic.

The thing is that I dont want to much network traffic and because of that I would prefere Alembics per frames.

Does somebody have a workaround?

Here is the setup:
https://we.tl/t-zDQjGu3Pgp

I use Houdini Indie 19.5 build 805
V-Ray for Houdini number:22687 hash:b4cd6d2 from 04 Apr 2024 03:28
V-Ray Core 6.20.05 [2f5d1705] from 29 Mar 2024


Cheers
Tobias

[tobiasroesli]

Nobody? So it seams my workflow must be Alembic's without $F

[bdancer]

If you are using per-frame Alembic - you have to have velocity and enable "Use Velocity Blur".

[tobiasroesli]

yeah I know that... so I gave the points a low value in v.x, v.y and v.z so the have something >0 before the alembic rop.
The points itself have no motion which I could generate with the pointvelocity sop. the motion gets generated by a transform node after the alembic sop.

When you use this method and also want to have subframes(geometry samples) for a smoother motion blur you also must generate the subframes in the alembic. Is that right?

Sorry for bothering, I just try to figure out how to render big amount of data efficient with Vray and Houdini and also the pro's and con's.

[bdancer]

> When you use this method and also want to have subframes(geometry samples) for a smoother motion blur you also must generate the subframes in the alembic. Is that right?

If you are using per-frame Alembic only velocity works.

[tobiasroesli]

ok, thanks that helped a lot to figure out a workflow