Corona-level Volumetric material support in VRay/VRay GPU?

[HowardDay]

This would be one of the major wishlist items I've got - I know the corona volumetric support is great - and there's just a sad lack of matching functionality on the VRay side. I'd hope you'd be able to add something similar to VRay 6.

[vlado]

What do you want to use such a material for? V-Ray already has a number of very good volumetric rendering options (VRayEnvironmentFog, VRayScatterVolume material, VRayVolumeGrid, the SSS options in the VRayMtl material) - which particular use cases do they not cover?

Best regards,
Vlado

[gandhics]

VRayVolumeGrid

I havn't met single artist who like the current way of shading VVG.
Also I just wanna have a material and re-use and pply to multiple grids or whatever.
I don't want tie shading with grid.

[Svetlin.Nikolov]

gandhics thank you, I've been doing changes for a while, preparing for a more decoupled volume shading, that could eventually end up as a material indeed, among other things. Of course keep in mind that this would be more flexible, but probably slower - currently when we know one voxel shader renders one single grid data, we can make a lot of assumptions and make it render much faster.

Can you share what you or every other artist don't like about the VVG shading though? I need something specific in order to make changes

Cheers!

[vlado]

Svetlin.Nikolov It is much easier to apply the same material to multiple volume grids and adjust the settings from one place rather than having to go to multiple grids to make sure they have the same settings, for example.

Best regards,
Vlado

[HowardDay]

What do you want to use such a material for? V-Ray already has a number of very good volumetric rendering options (VRayEnvironmentFog, VRayScatterVolume material, VRayVolumeGrid, the SSS options in the VRayMtl material) - which particular use cases do they not cover?
Best regards,
Vlado

So, what I'm looking for is the ability to apply a material to a 3d model in VRay GPU and have it be shaded like a volumetric VDB. This is supported in Corona: https://www.youtube.com/watch?v=t6R3JwCy02M Being able to do something like this in VRay would be great as well:
https://cdn.discordapp.com/attachmen...h-corona18.jpg
AFAIK, The volume shader needs to accept either black or white as fully transparent. It doesn't at the moment. There's also the issue that the sameish render in Vray takes 10 hours vs 20-30 min in Corona.

[^Lele^]

Svetlin.Nikolov It is much easier to apply the same material to multiple volume grids and adjust the settings from one place rather than having to go to multiple grids to make sure they have the same settings, for example

True, although to be fair saving and loading a render preset is mighty doable, and not too cumbersome, with the UI.
It does get quite repetitive after a while, the UI could be better (showing the user-saved presets, f.e.), and perhaps scripting access would help with massive changes.

All the above though gets sidestepped by the shader.

I am sure it would whet our appetite in terms of varied workflows (a shader can then be applied to any shader input location in max. i can imagine wanting to transfer a grid's attribute to a separate particle system, f.e., or have one more shader for foam, with the same kind of implicit primitives and structures available now in the PHX sources, applied to locations created maybe using separate particle systems, f.e. with tyFlow, or on a mesh's vertices if applied directly to a mesh node.).

I'm also quite sure there would be potential for performance loss, but perhaps with the opportunity of having a "free roaming" "pyro" shader users would be somewhat more lenient in that respect.

[Svetlin.Nikolov]

vlado , @^Lele, you guys have seen my long term plans in the last showoff, so all this would happen, but in this specific case something is very very wrong with the scene if it renders for 10 hours.

HowardDay, could you share your scene together with one cache file, or if it's confidential, at least screenshot all your fire, smoke opacity and smoke color settings together with the volume grid info rollout, so we can understand the setup and suggest how to get the same effect for a much shorter render time?

Of course I'd love to have our volume shader ready to apply over any geometry and shade it as a volume and this will be possible, but sounds like you don't need to wait for that long

[^Lele^]

vlado , @^Lele, you guys have seen my long term plans in the last showoff, so all this would happen,

Guilty as charged, i wanted to draw you out. /me hides

but in this specific case something is very very wrong with the scene if it renders for 10 hours.

Yeah, i cross posted with Howard (i was writing mine as he posted.).
I think he refers to scatterVolume, perhaps, or environment fog + gizmos?
vrayScatterVolume now has phase, btw, and you may want to revisit its performance...

[gandhics]

[USER="79057"]Can you share what you or every other artist don't like about the VVG shading though? I need something specific in order to make changes

Vlado and Lele already said what I want to said mostly.

Imagine you have many many volume grid for a sea of cloud.
Yes, I can script something. But, still artists need to manage all that. When artist do one more step, the chance for error increase linearly.

How about using some small mode to tree to set values?
The list goes on and on.

P.S. This is Changsoo. Jusy in case you don't know my id.

[Dave_Wortley]

A big +1 from all of us... would mean we could put the volume shader stuff in our material library system too.

[HowardDay]

I had a buddy of mine put together a demo scene of what we're talking about here:
https://cryohub.ams3.digitaloceanspa.../vray_demo.zip
Here's the latest vray version:

and the Corona version:

Apparently the Corona version is handling the opacity of the render much better, and the scattering seems richer somehow. There's also dark shadow artifacts in well-lit areas where there aren't any clouds. AFAIK it also doesn't function in VRay GPU. That's the main thing I'd like to get is this functionality in GPU/RTX.
Thanks!

[super gnu]

Just to add my comment here, ive not tried the volumetric stuff in Corona, but my big issue with scattervolume, sss2, translucency etc in max, is the map slots dont work volumetrically (unless this has changed in 6... ive got a rush job on at the moment and not had chance to check) . if, for example, you map the density using a 3d procedural, it does some weird variation of the surface, without affecting the internal structure. env fog handles 3d textures correctly of course, but is super slow.. and with a bit of fiddling, the volumegrid can be used, but neither are ideal for volumetric geometric objects.

[^Lele^]

Apparently the Corona version is handling the opacity of the render much better, and the scattering seems richer somehow. There's also dark shadow artifacts in well-lit areas where there aren't any clouds. AFAIK it also doesn't function in VRay GPU. That's the main thing I'd like to get is this functionality in GPU/RTX.

We can get the same result with a sphere and a vrayScatterVolume shader, in CPU.
Phase will help determine the look of thickness for a given scatter distance and radius. (see attached)

EDIT: thanks Olli!

[^Lele^]

Just to add my comment here, ive not tried the volumetric stuff in Corona, but my big issue with scattervolume, sss2, translucency etc in max, is the map slots dont work volumetrically (unless this has changed in 6... ive got a rush job on at the moment and not had chance to check) . if, for example, you map the density using a 3d procedural, it does some weird variation of the surface, without affecting the internal structure. env fog handles 3d textures correctly of course, but is super slow.. and with a bit of fiddling, the volumegrid can be used, but neither are ideal for volumetric geometric objects.

I agree it'd be nice if scatterVolume could read a distance texture volumetrically, f.e.
I also suspect it would be a heck of a lot of raytracing (which is why env fog is slow sampling textures).