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From: panisset@McRCIM.McGill.EDU (Jean-Francois Panisset )
Newsgroups: comp.sys.sgi
Subject: Fast frame buffer animation question
Keywords: bit-planes rectcopy
Message-ID: <1991May8.230648.17151@thunder.mcrcim.mcgill.edu>
Date: 8 May 91 23:06:48 GMT
Sender: panisset@thunder.mcrcim.mcgill.edu (Jean-Francois Panisset )
Organization: McGill Research Centre for Intelligent Machines
Lines: 27

Here is a question for all you GL gurus out there:

I am trying to generate short (a few seconds), fast (ideally 60 Hz) animation
sequences using small pre-computed images (probably around 128x128).
I have tried lrectwrite, but it seems
that the bandwidth from CPU memory to frame-buffer memory is just not there
(I have not tried this on a VGX though: what kind of throughput numbers can
you get? I'd be happy with 1Mb/s, happier with 4 Mb/s. Also, will setting
pixmode pixel size to 8 bits give me faster or slower performance?).
So the next idea
is to store all the images in the frame buffer and use rectcopy to bitblt
them onto the same spot. I get better results this way, but the problem is
that I can only fit a few images in the frame-buffer. Since my images a
grey-scale, I only need 8 bits for each image: I know I can specify source
and destination for rectcopy between the front and the back buffer on
a system, but what about within a single buffer? One of the systems is
a GTX with (I believe) double-buffered 24 bits: if I could use the extra
16 bits of each buffer which I don't need for my 8 bit images, I could
store many more images in the buffer.

Thanks in advance for any information you might provide,

JF Panisset



-- 
Jean-Francois Panisset                    
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