(Fixed, Open) [HOU-1397,1407] Merged volumes render incorrectly

[blented]

Merged volumes render incorrectly. The last-merged volume renders for all 3 volumes.

See the attached still, viewport on the right render on the left.

File:
bug file

Windows 10
Houdini 17.5.425
VRay 17.5.293_6c36393_5752

[chakarov]

Hello blented , unfortunately multiple volumes with same names are still not supported by the VolumeGrid shader. As a workaround you can use vdbcombine with operation set to "Add", this way the output is one volume only. I understand that with more complex simulations this workaround will be hard to manage, but it's the only way I can think of for now. Also in order to reduce vrscene filesize you should cache the output again.

[blented]

Unfortunately that doesn't work as we need to instance dozens of fires throughout the scene.

Even loaded in separate geometry nodes VRay still only renders the last-created volume.

This is a show-stopper for us so we're currently exploring other ways to render the scene :\

[Gosho.Genchev]

That should not happen. I'm on my way home and will check asap.

[blented]

Thanks Gosho I'll keep an eye on the thread and let you know if we find a workaround, exploring sop instancing options etc.

[Gosho.Genchev]

Even loaded in separate geometry nodes VRay still only renders the last-created volume.

This doesn't reproduce for me - I grabbed the individual volumes (Blast SOP with group 0, 1, etc) and brought them to a new Geometry node. Assigned the same volume shader and things worked as expected.

The problem *might* be related to the Pack SOPs if you've got them in your production scene, too. There is no point packing the volumes - if you have them on disk, we will grab them from there. If not, we need to bake them anyway.

File here: https://drive.google.com/file/d/1f6A...ew?usp=sharing

Hope that helps!

[blented]

Gotcha that seems to be what was causing the issue. We were packing them to instance them but are now trying to use the instance sop instead thanks for the clarification though.

[Gosho.Genchev]

Hey, Grant,

I've mislead you with my last post - turns out it's possible to treat each packed object as if it was a separate Geometry node - this makes it possible to instance the volumes around in a single node.

However, currently we are baking the volume to the VRScene when a Pack is used which probably won't cut it for you. The devs are working on improving this, too. I'll ping you as soon as this is taken care of.

Cheers!

[hsz]

Has this been improved btw?