Merge multiple VDBs

[JJ FX]

Hi, 

How can I merge multiple VDBs? Like VDB Combine (SDF Union).

Because when I usre just simple merge and then I convert to poly, all VDB objects have separate meshes. And I want only one mesh.

[cudarsjanis]

VDB combine does exactly what you need. check if you are working with fog volumes (density or whatever you have called them)

[JJ FX]

Yeah, but if i have 30 different VDB objects? VDB combine has ony 2 inputs

right now im doing: convert all VDBs to poly and then back to VDB. Can I somehow merge all vdbs into one without the conversion to poly?

Edited March 24, 2017 by JJ FX

[edward]

Probably need to do it in a loop then.

[cudarsjanis]

14 hours ago, JJ FX said:

Yeah, but if i have 30 different VDB objects? VDB combine has ony 2 inputs

right now im doing: convert all VDBs to poly and then back to VDB. Can I somehow merge all vdbs into one without the conversion to poly?

hmm 30 vdbs. That's an interesting problem there. Probably for each is the way to go, but how to properly set it up then. or volume wrangle/vop. I don't have time now to have a look at it, but I'm curious how to do it now.

[Atom]

You just use multiple VDB Combine nodes, kind of like compositing. Foreground over background. 15 nodes is not really a lot in a network.

[takanori]

Hi Try to use this shelf tool to make a chain of multiple VDB combine nodes by selecting & clicking once.

1. Select multiple VDBs.
2. Execute this script.

selected_nodes = hou.selectedNodes()
vdbcombines = []

for x, node in enumerate(selected_nodes):
    if x < len(selected_nodes)-1:
        vdbcombine = node.createOutputNode('vdbcombine')
        vdbcombine.setNextInput(selected_nodes[x+1])
        vdbcombine.setParms({'operation':'add'})
        vdbcombines.append(vdbcombine)

for x, vdbcombine in enumerate(vdbcombines):
    if x < len(vdbcombines)-1:
        vdbcombine.setInput(1, vdbcombines[x+1])

 

[Skybar]

No need for loops and stuff. Take one VDB and put it in the first input, merge all the others and put it in the second input. On the VDB Combine choose "Flatten All B into A" and choose the appropriate operation, like SDF Union for sdfs.

 

Edited March 29, 2017 by Skybar

[takanori]

@Skybar Yes! This is much better haha I was going stupid way, thanks!

Edited March 29, 2017 by takanori

[nAgApAvAn]

A new node in 19.0, I am currently using is vdb merge, which is very useful after vdb segmentation to combining back( not supports vector combines as of now)  https://www.sidefx.com/docs/houdini/nodes/sop/vdbmerge.html

Edited March 5, 2022 by nAgApAvAn