Incorrect decomposition result

[skyostil]

I noticed the library seems to lose some points in the result with some inputs such as this one:

#include "ConcavePolygon.h"

int main() {
  std::vector<cxd::Vertex> verts({
      cxd::Vec2({5.729166, 0.000002}),
      cxd::Vec2({2.604166, 0.000002}),
      cxd::Vec2({-0.520836, 3.125002}),
      cxd::Vec2({-6.770838, 3.125002}),
      cxd::Vec2({-6.770838, -3.124998}),
      cxd::Vec2({5.729166, -3.124998}),
  });

  cxd::ConcavePolygon poly(std::move(verts));
  poly.convexDecomp();

  std::vector<cxd::ConcavePolygon> result;
  poly.returnLowestLevelPolys(result);

  int i = 0;
  for (const auto& p : result) {
    printf("--- polygon %d:\n", ++i);
    for (const auto& v : p.getVertices())
      printf("%f, %f\n", v.position.x, v.position.y);
  }
}

In this case the point (-0.520836, 3.125002) is missing from the output.

[mjjq]

Thanks for your post, I can confirm that I get the same behaviour.

The cause seems to be due to the polygon slicing algorithm, specifically in slicePolygon(LineSegment segment) in ConcavePolygon.h. I'll attempt a fix and let you know when I've pushed it

[mjjq]

@skyostil I've pushed a fix to the dev branch a930b3d. Could you try it out? If it works I'll merge into master.

[skyostil]

Seems to work. Thanks for the quick fix!