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From: dfrank@CS2.CS.WSU.EDU ("Duane D. Frank")
Newsgroups: comp.sys.sgi
Subject: (none)
Message-ID: <9006091746.AA11156@cs2.cs.wsu.edu>
Date: 9 Jun 90 17:46:05 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 21

Hi there.
I'm new to this list, and perhaps this has been discussed before, but in 
any event I have a question about some clipping problems I have encountered.
Currently, we have a three year old 4D-60T (thought I believe it was 
updated to a 4D-70) and on this particular machine, it does not have the
capability to clip shaded polygons when using lighting models and so 
forth.  A page from the users manual mentions this problem.  What happens, is
when a corner or side of a polygon gets clipped off the edge of the screen,
the new polygon that is created has normals that are not defined, and have
not been interpolated from the other verticies of the polygon.  I had to
write some of my own clipping routines for this problem, but they are 
rather slow.  The solution they mention in the users guide says something
setting the viewport larger than the screen.  Unfortunately for the    
pplaications I am doing this will not work (I am doing some animation 
including "flying through" some of the objects).  
My question is this:  On any of the newer or more powerful machines has
this problem been corrected?  I had heard that this problem had been 
fixed on the Personal Iris, but I have not had an opportunity to test
this.  In any event, any replies would be appreciated, either directly
or by posting.
Duane D. Frank, (dfrank@cs2.cs.wsu.edu) or (22414843.WSUVM1.BITNET)