Previously, the lifetimes of anonymous attributes were determined by
reference counts which were non-deterministic when multiple threads
are used. Now the lifetimes of anonymous attributes are handled
more explicitly and deterministically. This is a prerequisite for any kind
of caching, because caching the output of nodes that do things
non-deterministically and have "invisible inputs" (reference counts)
doesn't really work.
For more details for how deterministic lifetimes are achieved, see D16858.
No functional changes are expected. Small performance changes are expected
as well (within few percent, anything larger regressions should be reported as
bugs).
Differential Revision: https://developer.blender.org/D16858
Recently a new geometry node for splitting edges was added in D16399.
However, there was already a similar implementation in mesh.cc that was
mainly used to fake auto smooth support in Cycles by splitting sharp
edges and edges around sharp faces.
While there are still possibilities for optimization in the new code,
the implementation is safer and simpler, multi-threaded, and aligns
better with development plans for caching topology on Mesh and other
recent developments with attributes.
This patch removes the old code and moves the node implementation to
the geometry module so it can be used in editors and RNA. The "free
loop normals" argument is deprecated now, since it was only an internal
optimization exposed for Cycles.
The new mesh `editors` function creates an `IndexMask` of edges to
split by reusing some of the code from the corner normal calculation.
This change will help to simplify the changes in D16530 and T102858.
Differential Revision: https://developer.blender.org/D16732
