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From: nwatson@ENUXHA.EAS.ASU.EDU (Nathan F. Watson)
Newsgroups: comp.sources.wanted,comp.graphics
Subject: Re: Ray tracing
Message-ID: <9106271635.AA21398@enuxha.eas.asu.edu>
Date: 27 Jun 91 16:35:18 GMT
References: <383@bibsyst.UUCP> <1991Jun27.155718.625@otago.ac.nz>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: nwatson@enuxha.eas.asu.edu (Nathan F. Watson)
Organization: Arizona State University
Lines: 30

In article <1991Jun27.155718.625@otago.ac.nz> grahaf@otago.ac.nz writes:
>In article <383@bibsyst.UUCP>, ingar@bibsyst.UUCP (ingar) writes:
>> I'm not sure i made myself clear the last time so I try again.
>> 
>> In my ray tracing program I am not able to ray trace cubes, or anything
>> that contains a strait line.
                   ^^^^^^

>Someone else had this problem and the answer posted was "You have a fish eye
>lens problem.

[ ... some diagrams suggesting that the original poster move the eye away
  from the viewing plane ... ]

The proposed solution involves diminishing the field-of-view angle by
moving the eye away from the viewing plane.  I do not believe this will
work as any projection of a straight line (or boundary between polygonal
patches) will be mapped to a straight line on the viewing plane (and
screen) no matter how close to the viewing plane the eye happens to be.
Since the original poster states that straight lines are curved, the
field-of-view angle is not the problem.

The problem may be in computing the vector from the eye through a given
pixel on the screen.  An error in this computation would almost certainly
map straight lines to curved lines.

---------------------------------------------------------------------
Nathan F. Watson                             Arizona State University
nwatson@enuxha.eas.asu.edu                Computer Science Department
"Remember:  No matter where you go, there you are." - Mr. B. Banzai