[HtoA] [Tip] Speeding up motion blur on VDB volumes


Merging your velocity vel.x, vel.y, and vel.z grids into a single vector grid using a Vdb Vector Merge node can speed up your renders.

vdb_vector_merge

You can safely ignore the “component grids have different transforms” warning on the VDB Vector Merge.  The x, y, and z components of the velocity have slightly different transforms because they located on the center of the cell faces in each direction; that’s coming from the marker-and-cell (MAC) grid used in the simulation.

If you really want to be precise with the velocities, you need to resample them on the same grid, say the density grid:
unnamed
Hat tips to Saber, Fred

[MtoA] Per-light AOVs for volumes


 

Arnold 4.2.12.2 added support for per-light AOVs for volumetrics.

Here’s how to set up per-light AOVs in MtoA 1.2.6.0:

  1. In the light Attribute Editor, enter a name for the light group.
  2. Create a custom AOV for the light group. Give the AOV a name that starts with “volume_”. For example, if the light group name is “red”, then the AOV name is “volume_red”.

aov_light_group