CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

Le Vendredi 02 Avril 2010 00:02:33, James Le Cuirot a écrit :
> On Thu, 1 Apr 2010 23:53:01 +0200
> "Laurent Rineau (GeometryFactory)"
> 
> <>
>  wrote:
> > > The Ray_2 class has a function called supporting_line(). It sounds
> > > useful but I'm not quite sure what it does. The docs say it returns
> > > the line supporting r which has the same direction. What is a
> > > supporting line exactly?
> > 
> > Given a (non-degenerated) ray, there is exactly one line that
> > contains it. That is the supporting line of the ray.
> > 
> > Another example: given a triangle in 3D there is exactly one plane
> > that contains it, that the supporting plane.
> > 
> > I think you get the point, now.
> 
> Hmm I wish I did. I'm lacking some background here. Doesn't a ray extend
> to infinity in one direction? How can a line "contain" that?

A line is something that extends also to infinity (like a ray, but in both 
directions). Do you mix up "lines" and "line segments"? Line segments are 
finite.

http://en.wikipedia.org/wiki/Line_%28geometry%29

-- 
Laurent Rineau, PhD
Release Manager of the CGAL Project       http://www.cgal.org/
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/