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From: kurt@cashew.asd.sgi.com (Kurt Akeley)
Newsgroups: comp.sys.sgi
Subject: Re: lines and libraries
Message-ID: <1991Apr22.163320.8755@odin.corp.sgi.com>
Date: 22 Apr 91 16:33:20 GMT
References: <1991Apr17.144853.17441@dsd.es.com>
Sender: news@odin.corp.sgi.com (Net News)
Reply-To: kurt@cashew.asd.sgi.com (Kurt Akeley)
Organization: sgi
Lines: 39

In article <1991Apr17.144853.17441@dsd.es.com>, pmartz@undies.dsd.es.com (Paul Martz) writes:
|> I have been developing some code on a Personal Iris GT which draws
|> primarily vectors. Using the v3f function, I was getting about 135K
|> vecs/sec, so I tried move/draw instead and started getting about 165K
|> vecs/sec. From this I deduced that move/draw is optimized for the
|> Personal Iris.
|> 
|> Then I sent the compiled executable to a friend who has a VGX. He
|> wrote back that vector performance was the worst he'd ever seen: 155K
|> vecs/sec! (Still using move/draw.)
|> 
|> So I have two questions:
|> 
|> 1) Is it normal to see move/draw perform better on a Personal Iris GT
|> than a VGX? I really should be using v3f for VGX machines, right?

Yes, you really should use v3f on GT, GTX, and VGX machines.  The VGX in
particular cannot parallelize move/draw syntax commands, and therefore
performs very poorly on them.  The Personal Iris is unfortunately optimized
for the soon-to-be-obsolete move/draw interface.

|> 2) Is the libgl_s.a library shipped with a Personal Iris different
|> from what's shipped with a VGX? I.e., could I have my friend
|> recompile/relink on the VGX and get different results?

Mixing libraries will not help, the slowdown is fundamental to the internals
of the VGX.

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

v3f calls are the future of the Iris Graphics Library.  If you choose to
take advantage of the performance advantage of move/draw calls on current
Personal Iris equipment, you should consider writing your code to use
v3f on all other platforms.

-- Kurt