* Only the volume object is exposed in the user interface. It is based on
OpenVDB internally.
* This does not include the viewport drawing or rendering code, that follows
in another code review. For testing, build the new-object-types branch so
that you can see the volumes.
* Hair and PointCloud object types are hidden behind a WITH_NEW_OBJECT_TYPES
build option. These data structures are not meant to be reviewed, besides
their integration into the rest of the code similar to volumes. The reason they are
included is since this will make it easier to cooperate on development for future
release, and avoids tricky merges.
* There is still an issue to solve with not enough bits being available for
FILTER_ID used in the file browser. A separate code review will be submitted
for that.
* This code review depends on D6695 (will be automatically applied when
using arc patch).
Relevant design docs:
https://wiki.blender.org/wiki/Source/Objects/New_Object_Types
https://wiki.blender.org/wiki/Source/Objects/Volume