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From: jdb@reef.cis.ufl.edu (Brian K. W. Hook)
Newsgroups: comp.graphics
Subject: Need help with algorithm
Message-ID: <27496@uflorida.cis.ufl.EDU>
Date: 18 Mar 91 13:36:10 GMT
Sender: news@uflorida.cis.ufl.EDU
Organization: UF CIS Dept.
Lines: 22

Hmm, this is a weird one, but while working on a Windows program I came
across a rather difficult (for me :-) but simple trig/geometry problem
working with the display surface.

Given the following:

   POINT P (Xp, Yp)
   ELLIPSE E (Center @ Xe, Ye)
   A rectangle bounding the ELLIPSE (W and H for width and height)

Find the location (X and Y) for the line (Xp,Yp) to (Xe,Ye) and the
ellipse's intersection....i.e. where do the line and ellipse intersection?

I am doing this calculation 10 times a second, so I am trying to keep it
fairly efficeint, and accuracy is not the most important consideration.
The display surface is using standard Cartesian coordinates (0,0 at bottom
left).

Please email responses,

Brian