vdb combine produces "errors" in combined volumes

[catchyid]

Hello,

I have 4 cloud vdbs that I combine at the end using vdb combine. The problem is if I render each cloud individually they look right in rendering, however if I combine the four in one big vdb the render looks "almost" perfect, meaning some areas could flicker for couple frames then go back to normal? has anyone experienced this problem before? the only solution now is to export each cloud independently instead....

thx

[ryew]

I experienced a similar issue a couple years ago when the VDBs were being recalculated every frame.  I can't recall exactly, but I believe we added a VDB Renormalize SDF to fix the majority of the problem frames so that might be worth a try.

[catchyid]

thx, will check that node to see how it works...i am using vdb for fog, so i am not sure a SDF function would work, anyways, will double check, thx

[KarlRichter]

What version of Houdini are you using? It might be related to this issue in the change log:

 

Houdini 18.5.460

OpenVDB support has been reduced to 7.1.0 pending investigation of a CSG Interesction failure detected in 7.2.1 version.

 

7.2.1 was introduced in Houdini 18.5.452   

[catchyid]

hi Karl, I am using 17.5...it's an older houdini version, so I assume it should be OpenVDB 7.1.0, however, I am pretty confident now that vdb merge in this houdini version as well is buggy: when exporting each cloud alone I get good render, when I merge all clouds I get flickering and bands...maybe it was not noticed/reported in houdini 17.5, but i think it's still there...

thank you Karl