Intersection.LineLine return true and valid parameters for nearly parallel lines

Rhino Developer
,
1

Hi guys,
I just encountered a problem with LineLine intersection method with two nearly parallel lines.

Rhino.Geometry.Intersect.Intersection.LineLine(edge1, edge2, out double t1, out double t2)

I was expecting the method return false or the parameters t1 and t2 are out of bounds, But this is not happening. I managed to solve this by a parallel check before computing the intersection.
Just so that you know!

2

Hi @torabiarchitect
the line-line intersection is supposed to find the closest points (shortest distance) between two infinite lines which are not perfectly parallel.
Jess

3

There is another overload of this method that lets you choose if you want to treat your lines as finite segments or not:

1 Like
4

Thank you both! the second overload worked for me without a double check. however the documentation remarks that I must filter the “nearly parallel” lines !
bool rc = Intersect.LineLine(lineA, lineB, out a, out b, tolerance, segments);

if (rc)
{
  double angle_tol = RhinoMath.ToRadians(1.0); // or whatever
  double parallel_tol = Math.Cos(angle_tol);
  if ( Math.Abs(lineA.UnitTangent * lineB.UnitTangent) >= parallel_tol )
  {
    ... do whatever you think is appropriate
  }
}