tighten CCW

[elalish]

Partially solves #502

Alternative to #507. I found a problem with CCW, where it was not properly conservative because the base could be up to twice as long as calculated if the v0 is near the midpoint between v1 and v2.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (7facd0e) 90.36% compared to head (4482ec7) 90.36%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #508   +/-   ##
=======================================
  Coverage   90.36%   90.36%           
=======================================
  Files          35       35           
  Lines        4431     4431           
=======================================
  Hits         4004     4004           
  Misses        427      427           

Files Changed	Coverage Δ
src/utilities/include/public.h	67.05% <100.00%> (ø)

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[pca006132]

Wow it is amazing that the cause of issue is so simple!

However, I found that although this fixes the simplified repro in #502, there is still triangulation error for the original mesh in openscad/openscad#4679, which you can reproduce by extracting the woodgrain.stl to test/models, and then run

#ifdef MANIFOLD_EXPORT
TEST(Samples, SvgBreak) {
  Manifold m1 = ImportMesh("../../test/models/woodgrain.stl");
  Manifold output = Manifold::Cube({145, 100, 1}, true) - m1;
  ExportMesh("SvgBreak.glb", output.GetMesh(), {});
}
#endif

And this no longer triggers any geometryErr.

[elalish]

Thanks, yeah I just noticed that your other simple polygon test is still failing - it's actually an unrelated issue. As part of debug I just realized intermediateChecks is not actually running during our tests like I thought it was. I am fundamentally misunderstanding something about how our ExecutionParameters are getting compiled.

[elalish]

Okay, I'm going to go ahead and merge this one and deal with the other triangulation issues on a separate branch.