Null Pointer Exception during Triangulation

Caused by: java.lang.NullPointerException
	at org.dyn4j.geometry.decompose.SweepLine.regular(SweepLine.java:258)
	at org.dyn4j.geometry.decompose.SweepLine.createTriangulation(SweepLine.java:128)
	at org.dyn4j.geometry.decompose.SweepLine.triangulate(SweepLine.java:79)

This seems to occur at random points during triangulation. I’m triangulating polygons sliced from an STL that had ~25000 triangles to create an STL surface, so there’s a lot of opportunity to hit edge cases I suspect. Unfortunately it also means that there’s a ton of prior calculations and tracking down why it happens is a minor nightmare…

For reference this happens via this code:

  public List<Triangle> toTrianglesInPlane(List<Point3D> points) {
    SweepLine sl = new SweepLine();
    List<Vector2> vector2s = projectToPlane(points);
    return sl.triangulate(vector2s.toArray(new Vector2[]{}));
  }

Since at this point I’m only dealing with planes orthogonal to the Z axis the project to plane code is trivial… There are multiple threads running this in parallel but the Point3D objects are immutable and as you can see the code creates a new Sweepline within each thread so unless you reference mutable statics it should be safe.

(Dyn4j 3.3.0)

[mtsamis]

@wnbittle @gus-asf I have reproduction polygons for this bug + some more cases for triangulation, I will upload them shortly.

@gus-asf I think your polygons are ill-shaped (self intersections probably?). But then SweepLine should have checks for those cases and throw an appropriate error.

[wnbittle]

I’m going to close this and track this issue from #75 . I’ve moved the sample you provided over there as well.