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From: jdonsbac@reverie.Prime.COM (Jeff Donsbach)
Newsgroups: comp.graphics
Subject: Re: CGM HLHSR in SunPHIGS
Message-ID: <1529@cvbnetPrime.COM>
Date: 28 May 91 16:34:55 GMT
References: <1991May27.185153.29565@dsd.es.com>
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From article <1991May27.185153.29565@dsd.es.com>, by rthomson@mesa.dsd.es.com (Rich Thomson):
> In article <1991May25.230056.26508@news.arc.nasa.gov>
> 	mckie@sky.arc.nasa.gov (Bill McKie) writes:
>>Apparently, there is still
>>no support for hidden line / hidden surface removal in the cgm output
>>workstation type (phigswstcgmout).
> 
> I don't use SunPHIGS, but from what I read in Appendix H of the PHIGS
> standard, CGM is 2D and not 3D.  I would suspect that this makes it
> impossible for the workstation to support HLHSR, which is a 3D
> concept.

Not at all. One of the final transformation in the graphics pipeline
is from 3D space to 2D space (ie the screen). The CGM output workstation
is just another 2D workstation. It should be possible, although using
a Z buffering technique probably wouldn't be.

Bill: we asked SUN for the same thing and their answer was "no". This holds
true for the latest SunPHIGS 1.4 FCS release and will also be true on the
X based SunPHIGS 2.0 as far as we've been told. The people we've talked to
at SUN didn't seem to know that much about the CGM workstation. Apparently,
this workstation type was written by Precision Visuals for SUN.

You could always do your own analytical HLHSR on your trees and construct
new trees with your lines and surfaces removed. That's probably not the
answer you wanted, but it would probably be faster than waiting for SUN
to give you what you want.

-Jeff

==========================
Jeff Donsbach, Computervision,  A Prime Computer Company, Bedford, MA 
UUCP: {decvax|linus|sun}!cvbnet!jdonsbac | Internet: jdonsbac@cvbnet.prime.com
"Hermits have no peer pressure" - Steven Wright