Fog does not work if the camera is inside the fog volume - help please!

[james_malloch]

Vray fog does not render fog correctly when the camera is inside the fog volume.

Here is what I have tried:

> Parent a polygon sphere around the camera, with a transparent shader on the sphere. This half works, the fog is generally visible from inside the fog volume, but objects inside the volume are not affected by the fog (serious problem).
> Tried with Vray VrayEnvironmentFog and Vray simpleFog.
> Vray SimpleFog sporadically works on a Maya volume primitive, but I only have this working on a single cube volume primitive from a legacy project, and cannot get this to work again (and definitely not with a custom poly object).

I need a working fog volume that renders from the outside and from within, for a seascape/underwater video. So far I've spent countless days trying to work this out - so any help would be greatly apprciated!

The attached screen-grabs show the issue.



Windows 10 x64
Maya 2023.1 (and Maya 2019).
V-ray 5.2 and 6

[viktor_angelov]

Hello James,

As we have discussed, the issue with the objects not being affected by the fog is escalated to Jira (VMAYA-11535) and we will be contacting you as soon as we have more information about it.

Regarding the needed set-up - Have you had time to try the Volume Grid workflow that was recommended?
You simply attach a VolumeNoise texture to the Attribute Editor > Rendering > Smoke Opacity of the VolumeGrid and adjust the Constant Color and Simple Smoke Opacity until your goal is met.

Please, let me know how it goes.

[intercard]

hello Mate!!

It’s normal because one object or poligon is not a Volume! You will need use the volume ! Try it

go to menu > create > volume and select one ! And apply VRay fog environment to volume !

regards

[james_malloch]

Hi Carlos - thanks for your message!

It would be good to know your method for attaching the Vray fog to the Maya volume primative. Here is the method I use:
> Create cube, cone or sphere volume primative (Menu>Create>Volume Primatives).
> Attach a Vray volume fog into the Shading group's volume slot (use either VRayEnvironmentFog or VRaySimpleFog).


I have experimented with the Maya volume primitives - I have one legacy Maya scene where I have a volume primitive that has working VRaySimpleFog, but I cannot reproduce it. Also, I cannot work out a method to feed a diffrerent polygon shape into a Maya 'volume primitive' (this would allow me to use my legacy volume shader cube as a foundation for a more complex fog object).

From speaking to the guys at Chaos, there seems to be a general bug with the fog if applied to polygon meshes if the camera is inside the object. As a workaround, suggested by Victor, I'm currently looking at the Vray VolumeGrid for fog.

Any suggestion would be appreciated!

James

[intercard]

Hello James !!!

So yes for complex models You will need use the VolumeGrid but for this method you will need modeling first and export it like as vdb or alembic cache or others format. now male the volume grid and import your volume model but maybe you cant use vray environment fog because the VRay VolumeGrid has its own material settings by default for liquids, fires, fogs...

tip: use the complex form when recording outside and use the primitive volume when the camera is inside

hugs

[yolov]

Hi @james_malloch,

The suggested approach to using a sphere around the camera will also require adding the same volume shader to the sphere (the one that's attached to the fog container).
You will also need to reverse the sphere normals and it should work.

Generally, VRayEnvironment fog can be used as an environment volume, inside a container or inside a gizmo - the setups for each is outlined here: https://docs.chaos.com/display/VMAYA...Fog-HowtoSetUp

Based on what you're describing, it sounds like the container (with a sphere with reversed normals around the camera) or an environment "gizmo" is what you need.
Let me know if that works.

[james_malloch]

Hi Alex (yolov), thank you very much for your suggestion.

I have experimented using your method described. I can get the camera to work correctly if the VRayEnvironment is not constrained to a gizmo/object volume. But if the fog is constrained, then the fog still does not work if the camera is inside a volume. I am creating an underwater scenario and I need to constrain the underwater fog to a volume.

I have experimented with the VrayVolumeGrid which almost worked, but the volume seems to not transmit correctly detail from objects placed behind the volumeGrid (so I cannot use this for the underwater fog).

Thanks,
James