This adds support to render PointCloud motion blur from a standard
"velocity" attribute.
This implementation is similar to that of the Mesh geometry, and
perhaps some code could be deduplicated through a more generic API.
`mesh_need_motion_attribute` was renamed `object_need_motion_attribute`
as it does not really require a mesh and moved to `util.h` so that
it can be shared.
This fixes T94622.
Reviewed By: brecht
Maniphest Tasks: T94622
Differential Revision: https://developer.blender.org/D13719
This add support for rendering of the point cloud object in Blender, as a native
geometry type in Cycles that is more memory and time efficient than instancing
sphere meshes. This can be useful for rendering sand, water splashes, particles,
motion graphics, etc.
Points are currently always rendered as spheres, with backface culling. More
shapes are likely to be added later, but this is the most important one and can
be customized with shaders.
For CPU rendering the Embree primitive is used, for GPU there is our own
intersection code. Motion blur is suppored. Volumes inside points are not
currently supported.
Implemented with help from:
* Kévin Dietrich: Alembic procedural integration
* Patrick Mourse: OptiX integration
* Josh Whelchel: update for cycles-x changes
Ref T92573
Differential Revision: https://developer.blender.org/D9887
