Path: utzoo!utgpu!water!watmath!watcgl!watsol!bmacintyre
From: bmacintyre@watsol.waterloo.edu (Blair MacIntyre)
Newsgroups: comp.sys.amiga
Subject: Window Clipping
Keywords: graphics, 3-d, clipping
Message-ID: <3060@watcgl.waterloo.edu>
Date: 27 Jan 88 16:06:06 GMT
Sender: daemon@watcgl.waterloo.edu
Reply-To: bmacintyre@watsol.waterloo.edu (Blair MacIntyre)
Distribution: na
Organization: U. of Waterloo, Ontario
Lines: 35


I have recently started a three-d fly-down-the-tunnel type game ( for
the fun of it ).  As anyone who has ever done three-d anything knows,
this requires a lot of line clipping after the three to two-d
transformation.  I was under the impression that the layers library
would handle this, but ...
  when I get line that go very far off screen, the line drawing routines
behave very strangly ( I first thought it was the program, but when
I wrote my own clipping routine, everything started working ).
The strange behaviour was as follows:
 - draw a line from point a to point b, both onscreen.  ok.
 - draw a line from point c to point b, with point c far of to the
   lower left of the screen ( ie. large +y, large -x ).
   - the line drawn:
     - does not connect with point b.  It connects corrently in the
       x direction, but they values are off.
     - is not even a line.  The result is a jagged series of vertical and
       sloped connected line segments.

Anyone seen anything like this?  Is the layers library supposed to handle
this offscreen clipping?  Or, if I have to continue to clip myself, does
anyone have a very efficient clipping algorithm?

Help!!

Thanx in advance,
Blair

===========================================================================
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