Line2d.intersectsLine(Line2D line) ?

[Rod Nibbe]

The Line2D class has a boolean method, intersectsLine(Line2D line), that
tests if two Line2D objects intersect. Why do you suppose it's boolean
instead of, say, returning a Point2D object with the actual point of
intersection, or null if they don't intersect? The method has to compute
the intersection anyway, so why not return the result?

I realize it's relatively simple to do this in a separate method, of
course, but it just seemed so obvious that the caller might actually
want the point of intersection -- like me!

-RKN

 

[Jacob]

The Line2D class has a boolean method, intersectsLine(Line2D line), that
tests if two Line2D objects intersect. Why do you suppose it's boolean
instead of, say, returning a Point2D object with the actual point of
intersection, or null if they don't intersect? The method has to compute
the intersection anyway, so why not return the result?

I realize it's relatively simple to do this in a separate method, of
course, but it just seemed so obvious that the caller might actually
want the point of intersection -- like me!

I think Line2D does this check *without* computing the
exact point of intersection, maybe due to performance
as this might be critical code?

Also, the computation is not as straight forward as you
might think; Look at the method findLineSegmentIntersection()
in http://geosoft.no/software/geometry/Geometry.java.html
where this problem has been solved.

 

[Rod Nibbe]

Yeah, it occurred to me after submitting my post that what you said
could be true, that the implementation doesn't need to compute the point
of intersection.

Thanks also for the link to the code. I have an old Fortran
implementation around here somewhere, and my recall is that the algebra
wasn't too complicated.

-RKN