Custom Loop Normals are normally encoded relative to the default
normals, similar to normal maps, allowing them to naturally follow
mesh deformations. Changes to mesh topology however often result
in nonsensical effects that are not desired.
The Remove Doubles operation especially (now known as Merge By
Distance) is intended as a purely topological operation, and
definitely should not change the vector of the custom normals.
This patch implements that behavior by converting the relative
encoding into an absolute vector layer for the duration of the
operation. It also modifies other Merge types in this way for
consistency, the Rip operator as their inverse counterpart;
and also Delete, Dissolve, Connect Path and Knife operators
as other examples more related to topology than shape.
On the technical side, this ports mesh_normals_loop_custom_set
to BMesh, and then uses a temporary Custom Data layer to store
the normals as vectors for the duration of the above mentioned
operations. When the normals are converted back to custom data,
the caller can choose whether to mark edges as sharp to preserve
distinct normals, or just average them instead. All but Remove
Doubles choose to average for now.
Differential Revision: https://developer.blender.org/D4994
Note this only changes cases where the variable was declared inside
the for loop. To handle it outside as well is a different challenge.
Differential Revision: https://developer.blender.org/D7320
clnor editing code was simply not checking at all whether it has
something to work on... Guess nobody had idea to edit custom normals on
a mesh that has no normals before! :P
This should probably be handled in a poll function too, to completely
disable those tools when there are no faces/loops, but let's keep it to
minimal changes at that point.
Merge code will generate temp normal editing data for affected loops,
but since it will later (by setting some edges/faces to smooth) alter
and extend affected clnor spaces, it will also need temp normal editing
data for some other loops around those vertices...
Using those clnor editing data in that code is a bit of an abuse, but on
the other hand that struct stores exactly what we need.
So simply added an option to generate that editing data for all clnors
of affected vertices.
Existing code was not really handling well cases were only edges or
faces were selected (with match select modes).
In those cases, we can assume user want to only affect loop normals of
selected faces/edges, not all lnors of all (indirectly) selected verts.
Also refactored the code a bit to move whole 'loop to edit' selection
process into its own single function.
BF-admins agree to remove header information that isn't useful,
to reduce noise.
- BEGIN/END license blocks
Developers should add non license comments as separate comment blocks.
No need for separator text.
- Contributors
This is often invalid, outdated or misleading
especially when splitting files.
It's more useful to git-blame to find out who has developed the code.
See P901 for script to perform these edits.
Second part of the fix: do not try at all to compute normals in degenerated
geometry. Just loss of time and potential issues later with weird
invalid computed values.
