The version of BM_elem_attrs_copy that took a map used a reference
the version without a map didn't, which is fairly confusing.
Pass by pointer now unless this is part of a wider refactor
to move to references everywhere.
Continuation of fix for #115776. Removes attribute copy functions
that calculate the map inline, this is error prone as it's easy to
call these functions from a loop which may result in poor performance.
Fixes#115776
Create a minimal structure that contains the instructions necessary to
copy from one custom data format to another. This structure is similar
to the one used in dfacaf4f40. It should have been used in
9175d9b7c2, which instead introduced quadratic performance
relative to the number of layers when copying every element.
In this commit, copying the entire mesh and adding new custom data
are explicitly changed to use the new map to speed up copying many
elements at a time.
The non-map attribute copy functions are also changed to check for when
the source and result BMeshes are the same. In that case it's much
faster to call the "same format" function from 9175d9b7c2.
For numbers, the timings are arbitrarily influenced by how many layers
I add in my testing. With 50 or so layers, a 10x difference is easily
observable though.
Pull Request: https://projects.blender.org/blender/blender/pulls/115824
Overload the attribute copy function for each element type, avoiding
the switch of different abstraction levels. The two extra arguments
besides the meshes and elements were constant, so the resulting
logic can be inlined as well.
When the BMesh source and result arguments are the same, restore
performance lost by 9175d9b7c2, which made copying layers
have quadratic time complexity. When we know the custom data format
is the same between the source and result, the copying can be much
simpler, so it's worth specializing this case. There is still more
to be done, because often we only know that the two meshes are the
same at runtime. A followup commit will add that check.
The quadratic runtime means performance is fine for low layer counts,
and terrible with higher layer counts. For example, in my testing with
47 boolean attributes, copying 250k vertices went from 2.3 seconds to
316 ms.
The implementation uses a new CustomData function that copies an entire
BMesh custom data block, called by a function in the BMesh module
overloaded for every BMesh element type. That handles the extra data
like flags, normals, and material indices.
Related to #115776
For now it has the same implementation as the function that allows
passing separate source and destination custom data formats. But
copying to the same format can potentially be much simpler.
