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From: vrm@blackwater.cerc.wvu.wvnet.edu (Vasile R. Montan)
Newsgroups: comp.sys.mac.programmer
Subject: Optimizing animation processing speed
Message-ID: <1776@babcock.cerc.wvu.wvnet.edu>
Date: 18 May 91 01:46:10 GMT
Sender: news@cerc.wvu.wvnet.edu
Reply-To: un020070@vaxa.wvnet.edu
Lines: 33

I am in the process of writing a program that does some pretty
complicated animation.  In the version of the program I've got now,
things are just running too slow.  I've got to figure out how to
make things run faster.  (I'm already on an 030 machine with a
math coprocessor, so running this program on, say, a Plus would be
just intolerable.)  I'd like to run my scheme past you; could you
all please suggest places where I could speed things up?

In this animation, I am moving icons around on the screen.  I
have two offscreen bitmaps.  The first offscreen contains the
background art, which is slow to draw; this way, I only have to
draw it once.  I continually CopyBits this whole bitmap into
the second bitmap.  I draw the icons the second bitmap, then
copyBits the second bitmap onto the screen.  This whole process
happens every event loop.  (Slow as this sounds, I have reason
to believe that this is actually not the big time-consumer.)

Each time I plot an icon, I GetIcon it, then draw it using copyBits,
then ReleaseResource it.  Now, if I'm not mistaken, this doesn't
actually purge the icon from memory, right?  If something else needs
the memory it will write over it, but if nobody needs the memory,
the icon will hang around until the next cycle, and GetIcon will
just give me a handle to the icon in memory, right?

In doing the calculations for the animation, I frequently refer
to complex data structures by handles.  Is this a particularly
slow way of doing things?  Could I speed things up appreciably by
locking the handles and using more Pascal WITH statements?

Any suggestions?

--Kurisuto
un020070@vaxa.wvnet.edu