Build a Volume/VDB Visualizer

[johnnyquest]

Some bullet points

• ~let's focus on VDB-style volumes mostly (provide option to convert input(s) to vdb)~
• ~volume (field) selector (visualizing just a single volume/field)~
• ~support for scalar (density/temp/etc) and vector (vel) type fields~
• optional VDB diagnostics before, e.g. catch NaN voxels (e.g. coming from potential flow node?)
• ~point jitter (0..1 where "1" is one voxel jitter)~
• ~volume intrinsic transformations!~
• ~downres before visualize~
• ~color visualizer: ramp w/ min/max values, automatic/get buttons~
  • ~should work both for scalars and vectors (vector length)~
  • ~Alpha support for visualization~
  • ~pscale support for visualization (disc point display type)~
• ~direction visualizers: simple vel direction vector OR volume trail~ -> just volume trail, that should be fine
  • ~alpha support~ / curve width support: needs to be turned on on obj level? :(
• clipping/trimming
  • ~usual single-voxel clipping plane thing~
  • ~optional second input with a bbox, for clipping~ (clip the volume before converting to points?)
  • trimming below min / above max values (both optional)