Mesh invariants imply that edges and faces must be unique, so things
like reversed edges or duplicate faces with equal vertices are invalid.
For this reason, every time we generate new elements we have to ensure
that all new elements are unique between each other and already existing
elements. The recent refactor (ea875f6f32) introduced a new
algorithm to generate new mesh elements, and deduplication of new
elements was also a part of it. The problem is that the deduplication
only guaranteed that the original elements and new elements don't
overlap; deduplication between each new elements is not complete.
To solve the problem both new triangles and new edges have to be
deduplicated, even if there is no duplicates. Just to know this we have
to build a hash sets.
Triangle deduplication is a special part of the triangulation code,
but edges already handled elsewhere in the code base.
This refactor fixes this by replacing the original approach with one
which guarantees distinct faces and edges in the result.
Unfortunately, this fix increases runtime of the node 10x for a simple
cube with 500-vertex sides. It should be possible to make the
performance better again, but that requires more work.
Other work had to be done to enable this, so this depends on:
- [x] 157e7e0351
- [x] fa8574b80b
Co-authored-by: Hans Goudey <hans@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/147634
bfb0d2ad20