V-RAY Proxy Alembic particle render issue

[gramx]

Hi

We are working on a project where we are using V-Ray MeshProxy's to render alembic particle caches from Houdini. We did several tests and it all worked great!! very nice feature

Now we are rendering several production scenes and we are finding that chunks of the particles are not being rendered on certain frames, and we can't find a fix.
If you isolate the proxy it renders correct or if you switch motion blur off then it renders with the environment correct.



Anyone having similar issues? Is there anything we can do to fix this? Thanks for help!

Graham

[vlado]

It would be best to get me a scene to vlado@chaosgroup.com so that we can debug it to see what's wrong. It might be something in the cache file itself, but it's hard to say without looking at it.

Also, a more reliable way to approach this could be to convert the Alembic caches to .vrmesh files using the ply2vrmesh tool.

Best regards,
Vlado

[gramx]

I'm trying to setup a simple scene as these caches are massive, but I've been unable to re-create the error. I will try and isolate a frame so I can send it to you.
I have also found that its only happening when I have multiple proxy's in the scene.
If I convert to a .vrmesh will the particles be saved as sphere geometry or will they stay as particles, as there are millions of particles in the cache.
Thanks
Graham

[vlado]

In the .vrmesh they will stay as particles.

Best regards,
Vlado

[vlado]

Btw which V-Ray version you are using?

Best regards,
Vlado

[gramx]

Ok, I will give that a try. I have tried both 3.00.02 and 3.00.07
Thanks
G

[vlado]

Ok. Then we will really need a scene to figure out what goes wrong.

Best regards,
Vlado

[asen.atanasov]

Have you tried to turn "Recompute bounding box" on? If the stored bounding box in the file does not include the velocities it might happens such a thing.

Best regards,
Asen

[gramx]

Yes, we have tried that, with no luck. We are playing around with some different alembic export options to see if this helps. We seem to get the errors on different frames each time we generate the alembic file.
Thanks

[vlado]

Yes, we have tried that, with no luck. We are playing around with some different alembic export options to see if this helps. We seem to get the errors on different frames each time we generate the alembic file.

Is it consistent though? (i.e. if you re-render the same frame, you get the same wrong result)? What happens if you try to import the Alembic directly in Maya (f.e. with Exocortex)?

Best regards,
Vlado

[gramx]

Hi, I have managed to create a cache with just two frames that causes the issue. The error is consistent but it changes depending what other geometry is in the scene, so in this sample scene if you hide a couple of the proxy objects then the chunk missing from the alembic file changes, it does look like some sort of bounding box error. Here is link to our file :-
https://dl.dropboxusercontent.com/u/...mbic_debug.zip
Its 100meg.
If you have any problems downloading then let me know. Thanks

[vlado]

Yes, I got the files and I can reproduce the issue. Looking into it now.

Best regards,
Vlado

[vlado]

This will be fixed for the next nightly/stable builds tomorrow - if you don't have access to the stable builds, please email us to support@chaosgroup.com and ask for them.

Best regards,
Vlado

[gramx]

Thanks, Vlado
I will download tomorrow and test.
Graham

[gramx]

OK, I have downloaded nightly/stable builds and its now working with my test thanks
We will update a few farm machines and do some more complex tests next. I will let you know how we get on.
Thanks
Graham