Tips on Rendering VDB Volumes with Volume Grid shader QUICKLY!

V-Ray V-Ray for Houdini General
1

Hi All,

I have a simple test scene setup where I’m instancing some cloud VDB’s around on a grid (via ‘copy_to_points’) to make some cloudscapes.
The VDB’s have a Volume Grid shader applied, and are rendering correctly - however I’ve noticed that I don’t seem to be able to use really low sampling settings on the Image Sampler to achieve _very fast and noisy quick test renders_.
Even with Min & Max Samples = 1, and the AA Noise Threshold at 0.5, I am still getting ‘clean’ renders; yet they are much slower than I want to be working - i.e. I’m looking at rendertimes around half an hour+, whereas I’m trying to churn out super noisy frames which finish in a couple of minutes so I can iterate quickly…
Any tips - it’s like the Volume Grid shader seems decoupled from the AA Image Sampler - I’m sure it’s not; I’m sure there is a setting somewhere I’m overlooking but I don’t know what it is…

Vray 5 for Houdini…

Any help most appreciated.

2

where you gonna see the difference in speed is on the shader itself, play with the sampling go higher if you want to get quicker result.

Also, if you use the GPU is way faster than the CPU to get results with volumes in general.

3

I can only speak for maya, but I think you have to switch to ray-traced light scattering.
if this doesn’t work try disabling light cache. Can’t check myself right now. But I believe it’s one of the two settings

4

Dear sv, hello. Please observe that the following is done:
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  1. Volume Light Cache must be OFF
  2. Light Scattering Type must be set to Ray-Traced
  3. Optimize Big Volumetric Grids must be OFF

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Best regards,
TS