Two problems were fixed. One, the code for dissolving vertices
left a face around if dissolving a vertex would leave less than
three vertices. Instead, the face should be deleted.
Two, with transformations like "rotate 180 degrees", this should
be no problem with exact, but the current transformation matrix
has very small non-zero entries where it shouldn't. Cleaning the
transformation matrix makes it more likely that user expectations
about coplanar faces will be fulfilled.
The code for determining coplanar clusters had a bug where it would
miss some triangles. The fix for now is to just put triangles in
the cluster if their bounding boxes overlap. This works but maybe
makes clusters bigger then they have to be. I'll follow this commit
with work on making the CDT routine faster when using exact arithmetic.
Also removed a lot of unused code, and added some new intersect
performance tests.
The code that decided to use a faster double version of plane
side testing forgot to take an absolute value, so half the time
the exact code was being used when it was unnecessary.
The code to detect non-trivial coplanar intersection sometimes
falsely said there wasn't one. This caused some coplanar intersections
to be missed. Also added a test for this case.
Instead of calculating exact normals for all faces, just do it
for those that potentially intersect. A big improvement for dense
meshes that only intersect in relatively few places.
The code that found coplanar clusters was not updating a bounding box.
Also, code that was detecting non-trivial coplanar intersects was
slightly wrong, but that would not have caused any functional problems.
This is for design task T67744, Boolean Redesign.
It adds a choice of solver to the Boolean modifier and the
Intersect (Boolean) and Intersect (Knife) tools.
The 'Fast' choice is the current Bmesh boolean.
The new 'Exact' choice is a more advanced algorithm that supports
overlapping geometry and uses more robust calculations, but is
slower than the Fast choice.
The default with this commit is set to 'Exact'. We can decide before
the 2.91 release whether or not this is the right choice, but this
choice now will get us more testing and feedback on the new code.
