UE 5.5 Heterogeneous Volumes (with VDB) issues

Development Rendering
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1

Hello,

I wanted to try using VDB clouds with unreal engine’s base material for heterogeneous volumes or even make a custom material for it but I realized there was an issue where the rendering of said heterogeneous volumes were having the priority over volumetric clouds.

In my case I wanted to have a set of global clouds (volumetric material on the volumetric actor) and have some local clouds at desired locations but it happens that the VDB clouds in said volumes are always rendered on top of any volumetric clouds which completely break any sense of realism.

Example in case I was not clear enough :
-1 big volumetric cloud 1km away from the camera
-1 VDB cloud 2 km behind the first cloud
=The VDB is always visible in front of the first volumetric cloud.

Is it a known “bug” and if so do we have any informations on if it will be fixed so that they can coexist?

View on the side

Screenshot 2025-02-28 153331
Screenshot 2025-02-28 1533311093×578 302 KB

View on the front
Screenshot 2025-02-28 153337
Screenshot 2025-02-28 153337903×615 280 KB

Also on a side note but still related to heterogeneous volumes, some cvars don’t seem to be working anymore from 5.3 to 5.5.

r.HeterogeneousVolumes.IndirectLighting don’t seem to have any effect and I could not find if that was due to some settings I have in my project or any other kind of actors.
Some other cvars are not working anymore in 5.5 causing BP compilation errors as well.

Best Regards

2

Have you solved this issue? I have encountered the same problem at work and cannot resolve it promptly. Could you share your solution?

3

Hey, sorry for the late answer but I couldn’t find any workaround for the matter.

The only thing I know is that the blend mode of materials will have a different priority for the depth buffer. Meaning that if you need your volumetric clouds to obstruct say particles, blend mode must be set to masked or opaque but not to translucent. This could be an entry point for VDBS. Masked being the only option I know of that could be acceptable, we still need to “cheat” using some AA dither to have some kind of gradient transparency but as you might guess for visuals where a precise translucency is needed it just is a compromise and does not help either, maybe only in certain situations depending on people’s needs.

As for VDBs I did not try pushing further when I saw some cvars being bugged as well as having bad performances. Maybe did you find anything useful since January?