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From: pmartz@undies.dsd.es.com (Paul Martz)
Newsgroups: comp.graphics
Subject: Re: How do I draw a perspective view?
Message-ID: <1991Jun6.172459.13616@dsd.es.com>
Date: 6 Jun 91 17:24:59 GMT
References: <9106010027.AA01356@bruny.cc.utas.edu.au> <1991Jun3.213012.7393@cs.ubc.ca> <1991Jun6.002233.5415@vicorp.com>
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In article <1991Jun6.002233.5415@vicorp.com>, ron@vicorp.com (Ron Peterson) writes:
> In article <1991Jun3.213012.7393@cs.ubc.ca> mgobbi@cs.ubc.ca (Mike Gobbi) writes:
> [text on how to do perspective deleted]
> >
> >Note that you MUST clip any polygon which has ANY vertex behind the eye
> >(negative or 0 z-value) or else really wierd stuff will happen.
> >
> Is there a simple general method for doing perspective calculations that 
> works for ANY orientation of object, screen, and POV including situations
> where:
>    * part of the object is behind the POV and part in front or 
>    * if the object crosses between octants of the coordinate system or 
>    * the object resides at the origin or
>    * the POV is inside the object being rendered
> or does it have to be broken into cases?

It does not have to be broken down into cases, as long as you:
	- Use a generalized viewing pipe, a la Foley & Van Dam;
	- Send every primitive through a clipping function after it
	  has been transformed to NPC space.
-- 

   -paul	pmartz@dsd.es.com
		Evans & Sutherland