Bounding box calculation can be a large in some situations, especially
instancing. This patch caches the min and max of the bounding box in
runtime data of meshes, point clouds, and curves, implementing part of
T96968.
Bounds are now calculated lazily-- only after they are tagged dirty.
Also, cached bounds are also shared when copying geometry data-blocks
that have equivalent data. When bounds are calculated on an evaluated
data-block, they are also accessible on the original, and the next
evaluated ID will also share them. A geometry will stop sharing bounds
as soon as its positions (or radii) are changed.
Just caching the bounds gave a 2-3x speedup with thousands of mesh
geometry instances in the viewport. Sharing the bounds can eliminate
recalculations entirely in cases like copying meshes in geometry nodes
or the selection paint brush in curves sculpt mode, which causes a
reevaluation but doesn't change the positions.
**Implementation**
The sharing is achieved with a `shared_ptr` that points to a cache mutex
(from D16419) and the cached bounds data. When geometries are copied,
the bounds are shared by default, and only "un-shared" when the bounds
are tagged dirty.
Point clouds have a new runtime struct to store this data. Functions
for tagging the data dirty are improved for added for point clouds
and improved for curves. A missing tag has also been fixed for mesh
sculpt mode.
**Future**
There are further improvements which can be worked on next
- Apply changes to volume objects and other types where it makes sense
- Continue cleanup changes described in T96968
- Apply shared cache design to more expensive data like triangulation
or normals
Differential Revision: https://developer.blender.org/D16204
The generic bounds utility used an incorrect initial value. The value
cannot be zero-initialized, because that breaks the case where all
values are greater than zero.
Finding the greatest and/or smallest element in an array is a common
need. This commit refactors the point cloud bounds code added in
6d7dbdbb44 to a more general header in blenlib.
This will allow reusing the algorithm for curves without duplicating it.
Differential Revision: https://developer.blender.org/D14053
