VrayVolumeGrid Fill?

[White Wizard]

Does anybody know a way to fill a volumegrid with voxels uniformly and quickly without having to import sims? I want to use it to make uniform fog because environmentfog is painfully slow.

[werticus]

There are ways to optimize environment fog. Increase step size and don't use gizmo falloff... No idea how to answer you actual question tho :P

[kagemaru]

If you want i can give you a box vdb file with increasing voxel size. I used as i think you are planning to do, filling everything and use it as an alternative to vrayenvfog.
You can very easily do it with houdini apprentice if you want, in this way you can optimize sizes based on your needs.

[White Wizard]

There are ways to optimize environment fog. Increase step size and don't use gizmo falloff... No idea how to answer you actual question tho :P

I'm fairly certain the only quality parameter available when using non textured fog is the subdivs. I believe step size only affects texture sampling although I may be wrong.

If you want i can give you a box vdb file with increasing voxel size. I used as i think you are planning to do, filling everything and use it as an alternative to vrayenvfog.
You can very easily do it with houdini apprentice if you want, in this way you can optimize sizes based on your needs.

Excellent. Thanks for the tip. No need to send me anything I'll get it from Houdini. How effective was this method compared to environment fog in your experience? I imagine you have much more control/speed.

[kagemaru]

Excellent. Thanks for the tip. No need to send me anything I'll get it from Houdini. How effective was this method compared to environment fog in your experience? I imagine you have much more control/speed.

Compared to envfog, when i used this method it proved to be super fast and very smooth. You won't get volumetric shadow though. Keep in mind that in some situations it can produce artifacts.
I'll attach a frame from a short i did. It also took the lighting from volumegrid lights coming from a fire simulation i had.

[White Wizard]

Compared to envfog, when i used this method it proved to be super fast and very smooth. You won't get volumetric shadow though. Keep in mind that in some situations it can produce artifacts.
I'll attach a frame from a short i did. It also took the lighting from volumegrid lights coming from a fire simulation i had.

[ATTACH=CONFIG]30986[/ATTACH]

Very cool. I'll have to try it out although I'm worried no shadows might be a deal breaker for my scenes. I wish environmentfog worked in RT GPU. I could crank out separate fog passes in no time.

[DaveGrafix]

I'm testing Houdini clouds in a city scene now, and am getting volumetric shadows... could be due to the resolution of your grid? Curious...

--Dave

[White Wizard]

I'm testing Houdini clouds in a city scene now, and am getting volumetric shadows... could be due to the resolution of your grid? Curious...

--Dave

I'd love to see a still of that if you are cool with posting it.

[kagemaru]

I'm testing Houdini clouds in a city scene now, and am getting volumetric shadows... could be due to the resolution of your grid? Curious...

--Dave

Yes, of course you'll get volumetric shadowing from smoke on other objects and viceversa: i was referring to a situation where you are inside the smoke (to simulate fog).
I don't remember why but when i did that scene i couldn't get correct volumetric shadows (i had a very heavy vdb so resolution wasn't the culprit), but i just tested and it worked as expected (maybe volumegrid has got some updates in the meantime?), so my bad, i wrote a silly statement, thanks Dave for the clarification!

[DaveGrafix]

I'd love to see a still of that if you are cool with posting it.

Sorry I didn't see this earlier! Here's a rough render, using a lower-res top/bottom gradient VDB as environment fog. Still needs work, but getting some nice subtle god-rays...