Currently `Mesh to Volume` creates a volume using
`openvdb::tools::meshToVolume` which is then filled with the specified
density and the class set to Fog Volume. This is wrong because
`meshToVolume` creates a signed distance field by default that needs
to be converted to a Fog Volume with `openvdb::tools::sdfToFogVolume`
to get a proper Fog volume.
Here is the description of what that function does (from OpenVDB):
"The active and negative-valued interior half of the narrow band
becomes a linear ramp from 0 to 1; the inactive interior becomes
active with a constant value of 1; and the exterior, including the
background and the active exterior half of the narrow band, becomes
inactive with a constant value of 0. The interior, though active,
remains sparse."
This means with this commit old files will not look the same.
There is no way to version this as the options for external band width
and not filling the volume is removed (they don't make any sense for a
proper fog volume).
Pull Request: https://projects.blender.org/blender/blender/pulls/107279
700d168a5c