Tomas Slancik

You can probably register node event callback [www.sidefx.com] for each HDA instance to handle hou.nodeEventType.ParmTupleChanged

You likely want to add it during HDA's OnLoaded callback as the node event callbacks don't persist between sessions

likely because you don't have UVs on the remeshed geo since displacement map relies on that

you may have some luck with Labs UV Transfer to transfer vertex uv attribute from original geo to remeshed geo

or alternatively you can create new UVs and bake the new displacement map

kta3d
...however, i have not found any way in Houdini to make a vdb that has anything other than a single 'density' attribute in a single channel. I would ideally like to channel-pack a VDB so multiple cloud/fog densities are stored into separate named channels/attributes (even if that doubles the file size)..

You can have multiple named float or vector vdb primitives in the geometry and when you save that geo into .vdb they all will be within the same single .vdb file