Path: utzoo!attcan!uunet!dino!ux1.cso.uiuc.edu!uwm.edu!zaphod.mps.ohio-state.edu!swrinde!kent
From: kent@swrinde.nde.swri.edu (Kent D. Polk)
Newsgroups: comp.sys.amiga.tech
Subject: PolyDraw replacement - waveform plotting
Keywords: PolyDraw, Blitter
Message-ID: <25661@swrinde.nde.swri.edu>
Date: 19 Mar 90 19:49:00 GMT
Distribution: na
Organization: Southwest Research Institute, San Antonio, Texas
Lines: 29


I have an A2500/20 and need to be able to draw 1k point waveforms very
fast (in a 512 pixel window). I have tried various schemes for
acquiring the necessary speed, but the best I can do misses what I need
by a factor of about 4. BTW, I really have to view all of the data -
i.e. I can't just plot data points that fall on pixel boundaries.

Generally, the fastest (safe) speeds I have obtained are by using
PolyDraw() to draw into a 1 bitplane offscreen rastport and then
BltBitMapRastPort() that bitmap to my display window rastport. I have
the plotting routine running as a process that I send messages to with
a higher priority than my data acquisition processes.

I tried hacking an assembler routine which uses the linedraw mode of
the blitter to draw into my offscreen bitmap, but to my amazement, it
was actually slower than PolyDraw (with the associated copying of my
ydata into an x/y pair array which I circumvented in my assembler
blitter draw).

Any suggestions for getting the speed I need out of this machine?
Would an assembler line draw routine be faster on the '020 than a
blitter one? If so about how much and does anyone have source I could
start with?

Thanks much
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Kent Polk - Southwest Research Institute - kent@swrinde.nde.swri.edu
        Motto : "Anything worth doing is worth overdoing"
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