VDB step size changing automatically in rendered view

[tombyrom]

Hello guys,
I am experiencing an issue which is hard to debug. I know VDB volume step size changed in the latest version to a % which is likely something to do with it.

This is on a scene which was only created in the latest version (no compatibility issues).

The issue is without changing the volume medium settings, upon loading the scene, sometimes the rendered result is different for the VDB volume even without changing the volume step percentage in the medium.

I then have to change the volume step % to get it back to what it should look like, but is actually the incorrect percentage. Then, after a load or two it changes appearance again based on the changes I had to make. Then I need to reset values to the original to get correct appearance. Ultimately I end up in an endless cycle of repeating the above.

This happens on VDBs from different sources so not limited to a specific VDB file.

I am using the default octane volume. I am not changing any of the default settings, simply adding a VDB file and a medium node (screenshot attached).

It is as if the medium is incorrectly reading the voxel size of the volume on load?

Just bringing to your attention. As it is quite annoying...

[tombyrom]

Also, switching to 2023 compatibility mode via the medium, upon reloading the scene this gets reset to the latest version and then again need to make the change to get back into compatibility mode

[paride4331]

Hi tombyrom,
I’m unable to reproduce the issue at medium volume. Could you share the file where you’re experiencing the problem?
Regards
Paride

[tombyrom]

To be clear the percentage does not change in the medium volume settings. It has the same value but when I reload the scene and hit render it renders completely different, mimicking a different step percentage. I then have to manually update step percentage setting to get it to look correct. Then reloading the file > hitting render, it looks different again and I need to manually update the step percentage.

Paride, I will simply the scene to only include the VBD, hopefully you can mimick the behavior, can I share it directly with you?

[tombyrom]

Paride, the simplified version I sent you doesn't seem to have the same issue and in the process of simplifying I overwrite the original scene, I loaded an automatic backup and the backup does not have the same issue. So no idea what was causing it!

[paride4331]

Hi tombyrom.
Try creating a new scene and then merging your scene with the issue into it. See if you encounter any malfunctions.
As you’ve shared the scene, I can’t download it. Please consider using WeTransfer or a similar service to share the file.
Regards
Paride

[tombyrom]

The issue has now fixed itself after loading a backup of the same scene and the simplified version of just the VDB also did not have the problem so it had to of been an issue with the original file. In the future I if I come up with a similar issue I will try what you said which is merge elements into a new scene. Thanks