Volumes shadow issue?

[grimm]

I did a ground fog simulation in Blender and rendered it out with Octane V3 but the volume shadows are very low quality, very voxel like. Here is the simulation:

https://vimeo.com/187772997

Is there something that can be done to improve the shadow quality? The step length was set to 2.0 and the scale set to 100. I didn't want to decrease the step length because it would have made the fog thicker.

Jason

[bepeg4d]

Hi grimm
the scale has a great impact, in theory, you should be able to reduce the step length until you are satisfied of the resolution, then you should reduce the density until you find the correct thickness.
ciao beppe

[grimm]

Thanks Beppe, I tried your suggestion, but the shadows are still not working like I think they should. I decreased the step to 0.5 and the scale to 10 and here is the result:

test1.png

It looks like the shadows are only generated from the step length and the scale is not part of the calculation. The shadows are way too dark and the edges are just as aliased as they were before. Maybe this has something to do with how I generated the VDB's in Blender?

[bepeg4d]

Hi grimm,
what happen if you maintain the scale at 100 and reduce the step length at 0.5?
In theory you should see a better result than in the animation, I guess
ciao beppe

[grimm]

I did try that but the fog gets way too thick and you loose that light wispy look I'm trying for. And the shadows are still aliased.

test2.png

[BorisGoreta]

I think you should increase simulation resolution.

[grimm]

Thanks Boris, that's what I was thinking too. I think there are two issues here, one the shadow resolution, and the other is that the shadows should be attenuated by scale as well as by the step length?

[haze]

May I have 1 or 2 VDB samples and an orbx please?

It seems that the resolution is too low, but please also check that alpha shadows are enabled.

[grimm]

Thanks Haze, I'm at work right now, when I get home I will push the files up to you. I hadn't thought about enabling the alpha shadows, I usually turn them off.

Jason

[haze]

Ok, when alpha shadows is disabled, the volume will cast a black shadow which will follow the outlines of the voxels themselves - this is probably the aliased edges you are seeing, and also why it seems the volume's density scale isn't affecting the shadow