Retiming VDB vs Retime houdini volume

[viki164]

Hello wonderful community,

I wonder if this is a known issue when using retime SOP with VDB's ?

I am experiencing some juddering in the velocity and pulsing effect in the beauty renders.

I am retiming by 0.1 speed with no sub frames caching. I imagined the new Retime node is suppose to be smart and doesn't need any incremental sub frame caching ? 

On the other hand when I converted those vdbs back to Houdini Volume , added a volume resize node with a bound along with some padding and then used Retime SOP with blend mode set to Advected.

To my surprise the velocity channels were properly interpolated and the renders were less flickering but at the expense of heavy cooking time and rendering. I did convert those houdini volumes back to vdb after retime sop.

The Retime sop doesn't fully support vdb for velocity interpolation to my experience ? I will be happy to be proved wrong and I wonder if others also have similar issues when doing a retime with 1/10th of its speed ?

Do you guys add a large static bound to your volumes before converting it to vdb or just volume resize node with some padding ?

Thank you !

p.s : retime with interpolate velocity often produces empty vdbs in velocity channel when used with vdbs but works fine with houdini volumes.

 

Edited February 26, 2021 by viki164

[tamagochy]

To interpolate VDB vel you need to separate vel for three floats x y z. And you need have only density and vel, if there are more floats channels retime will not work.

[viki164]

Thanks. I have been having success making other float field work like temperature and heat ! I will try to isolate the velocity vdb to see if it produces cleaner result as compared to houdini volume.