How to modify multiple VDB volumes using the Volume Wrangle SOP?

[magneto]

Hi,

 

I have a Cd standard Houdini volumes for x, y and z which are easily modified using the Volume Wrangle SOP, where I am basically setting the color of each voxel to relbbox(@P).

 

But the same thing doesn't work with VDB volumes. I tried the Convert VDB SOP which converted the volumes into VDBs that are separate just like the original volumes but after modifying them in the Wrangle SOP, there is no change in the output. The help card doesn't mention anything about not supporting VDBs. Is this the case?

 

Also using the VDB SOP, I can create a vector volume but unlike the standard Houdini volumes it creates a single volume storing the vectors, which doesn't do anything when I am using the same Wrangle code.

 

The Volume Wrangle help card also doesn't mention how to handle these volumes which are quite different than standard Houdini vector volumes.

 

Any ideas? I assume it's a simple thing I am missing or it's not supported fully.

 

 

Thanks

[pezetko]

Is this what you need?

vdb_color.hipnc

[magneto]

Thanks pezetko, it works great Also do you know how to initialize an empty VDB volume as created by VDB SOP? That's what I tried originally and when I use that in Volume Wrangle, it still shows up as "empty". I don't know how to ensure that it's initialized with voxels.

[tjeeds]

You use the VDB Activate node to turn on volxel in your empty VDB. You can specify a bounding box or use another VDB as a secondary input (this works nicely to use a low-res VDB to turn on the voxels of a high-res VDB)

[magneto]

Thanks tjeeds, that works great. I never used the VDB Activate node before. By bbox, do you mean using an expression because I couldn't find an automatic way to use the bbox of the input geometry. I also tried the second input.

 

It's not a big deal though, just curious