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From: greg@vecpyr.UUCP (Greg Millar)
Newsgroups: net.graphics
Subject: VDI/CGI
Message-ID: <277@vecpyr.UUCP>
Date: Sat, 3-May-86 22:13:41 EDT
Article-I.D.: vecpyr.277
Posted: Sat May  3 22:13:41 1986
Date-Received: Tue, 6-May-86 04:17:32 EDT
Distribution: net
Organization: Visual Engineering Inc
Lines: 33
Keywords: CGI VDI GraphCap Device-drivers


CGI/VDI is not a finalized standard yet.  I have seen a proposed C binding
but it is only proposed.  

The real problem though is that CGI/VDI, GKS and any other graphics
standard like these does not address the issue of device independence.
There is no such thing as a CGI standard device driver, or a GKS device
driver.  It is totally up to the implementor of CGI, GKS, etc to determine
how devices are handled.

We have approached the problem differently with graphcap.  Once you have
our GKS (with our vdi) and you want to add a new device driver, all you 
have to do is add a new graphcap entry (sort of like a termcap entry)
and now your applications can use this new device.  You don't need the
source to the GKS or VDI since you get the graphcap database in its
source form so you can change the device at will.

This seems to be the right approach to device independence, since none
of the currently proposed graphics standards really address the issue.
All the do is provide a standard programmer interface to the functions
of GKS, etc, not a standard device interface.




		
			Greg Millar

			...{ucbvax,decwrl}!dual!vecpyr!greg
			Visual Engineering, Inc.  
			2680 N. First
			San Jose, CA 95134
			(408) 945-9055