Terragen VDBs and C4D Octane

Started by BroBpony, July 10, 2022, 02:33:17 AM

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BroBpony

Tested out the Terragen VDB export for this scene that I rendered in C4D with Octane.
(Wasn't  sure if this is a scene that could go into the Image sharing as i'ts not technically a TG render)
The export is pretty nice, with my only feedback being that if a lower number of threads can be faster then it would be nice to have a thread count slider in the export window rather than only by command line.
Another thing I noticed is that for decent clouds you pretty much cannot do anything under 2000 million voxels (the clouds in this scene are 3000 million voxels and they didn't hold up at any closer range, you can see the lack of voxels more with the cubic look of the clouds in the top-down shot). This is not really a problem since you can just up the voxel count but it does do a weird mental disconnect where I expect the clouds at 100 million voxels to export like they look in TG render and it is slightly unnerving to have to increase by so much the voxel count.
Otherwise its really nice to have this on Windows and they look nice.

BroBpony

the top down shot.
The clouds have a slight cubic look to them, Octane does a nice job of smoothing out with a larger volume step but its still there.

pokoy

The voxels in TG are used for lighting/GI while the cloud's density is still calculated from the noise function (not limited by voxel count in its level of detail), that's how I understand it anyway. When you export to VDB you only get the voxels, not the detailed noise function that TG uses for the direct shading/density part. 
Bigger cloud layers will have a sparse voxel distribution even at maximum voxel count, only way to get around that would be to export multiple smaller cloud layers.

WAS

The shadows of the mountains look perfect in octane. The tree lighting blends nicely with the ground, not sharp and dark.

zaxxon

Interesting about the noise function/density relationship.  Does that mean that TG Clouds will always look better in TG then then the exported VDB's in other applications?  Nice work BroPony!   What's the render time in Octane with your examples?

WAS

Quote from: zaxxon on July 11, 2022, 10:57:49 AMInteresting about the noise function/density relationship.  Does that mean that TG Clouds will always look better in TG then then the exported VDB's in other applications?  Nice work BroPony!  What's the render time in Octane with your examples?

Sorta. I did some exports at ridiculous sizes that froze TG (had to set the settings in the TGD file itself and than run on my server), and it was a pretty close exact. But the settings are so high that TG application can't set them without crashing.

pokoy

Yeah, think of volume voxels (and VDB) like something built out of blocks, pretty much like some structure in Minecraft.
TG on the other hand uses its internal noise functions and can calculate them at pixel level, and uses voxels only to compute light propagation and GI within volumes. The fact that we can export VDBs is basically a side effect of TG using voxels.
At least that's how I understand it, judging by all my tests and VDB in other apps I guess this is more or less what's causing the difference.

BroBpony

Quote from: zaxxon on July 11, 2022, 10:57:49 AMInteresting about the noise function/density relationship.  Does that mean that TG Clouds will always look better in TG then then the exported VDB's in other applications?  Nice work BroPony!  What's the render time in Octane with your examples?
Thanks! It was a 54 minute render.
I render on a 2080ti.