CGAL users discussion list

[Jeffrey Bush <>]

Hi,

I am using AABB_tree to determine intersections between a plane (call it "h") and a polyhedron, resulting in a vector of segments ("segs"). However the following test fails:

h.has_on(*segs.begin())

This shouldn't be. However doing research I realized the result may be because of using Cartesian instead of Exact_predicates_inexact_constructions_kernel, so I switched to that. But still the same problem!

Running the debugger I get to this function:

  inline
  Uncertain<Sign>
  sign (const Interval_nt<Protected> & d)
  {
    if (d.inf() > 0.0) return POSITIVE;
    if (d.sup() < 0.0) return NEGATIVE;
    if (d.inf() == d.sup()) return ZERO;
    return Uncertain<Sign>::indeterminate();
  }

With the following value for d:

d = {

  _inf=5.6843418860808015e-014,

  _sup=5.6843418860808015e-014,

  tester={...}

}

It seems as though the d.inf() == d.sup() check should be first? It seems that if sup <= inf and inf > 0 or sup < 0, then the d.inf() == d.sup() can only be 0 == 0... (but I guess sup > inf - I don't understand exactly what this is all about).

Just for scale, my points have values on the order of 2500 and the plane is <0,0,1> -300. 

If this is right (and I could easily be, I don't know too much about double-precision mathematical testing), then what am I doing wrong? My meshes are LARGE so I don't want to use the infinite-precision numbers.

Thanks!

Jeff