VDB volume grid deactivating EnvironmentFog

[hombrezoo]

Hello, I've been doing some render tests with GPU and found something strange happening while trying to render a scene with EnvironmentFog and a VolumeGrid.
Tried many settings and used even render mode as "Volumetric Geometry" like it has been suggested in other threads but "volume grid" seems to cancel the "Env Fog" shader, even with no "VDB" connected to it. The funny thing is sometimes when rendering starts and creates the GI process you can see your EnvFog object or atmosphere been calculated but once it goes into bucket or progressive mode for the final render the EnvFog element disappears completely. It seems to be able to render both only when render mode is in the Mesh option but of course I want fog not a mesh.
already tried rendering in CPU mode and it does render both but I'm interested in using GPU for speed rendering reasons. Am I doing something wrong here?

Thanks in advance.

[georgi.zhekov]

Hello,

Currently using both VolumeGrid and EnvFog at the same time is not supported on the GPU. This is still in the to do list.
You will have to stick to CPU in this case.

[hombrezoo]

Thank you very much Georgi, forgot to reply last week.

[matanov]

You can emulate the fog in V-Ray GPU with an empty VolumeGrid and still use the cache with another VolumeGrid.

[hombrezoo]

Thanks so much Slizer, I read about that in a different thread, but should the fog element in the volume grid has to be a vdb itself? or is it possible to just create a volume grid in the scene and fill it right from the settings? I tried that but no luck. Can you elaborate a little more, it would be very much appreciated.

[georgi.zhekov]

Hey,

I'm afraid what Slizer suggests is only implemented in 3ds Max. It's still in the to do list for Maya.

But here is how it goes as a workflow (no need for vdb files at all) - use just an empty VolumeGrid and set it's Opacity to be based on Smoke and just offset the first point of the curve to be more than zero - note that this won't work at the moment.

What you can do as a workaround is to simulate a VDB that fills the whole grid and set its opacity to some really low value.

Cheers,

[hombrezoo]

Thanks again Georgi, I'll try using a VDB instead.

P