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From: dtt@unirot.UUCP (David Temkin)
Newsgroups: net.micro.mac
Subject: Animation Query
Message-ID: <798@unirot.UUCP>
Date: Fri, 27-Jun-86 10:36:20 EDT
Article-I.D.: unirot.798
Posted: Fri Jun 27 10:36:20 1986
Date-Received: Sat, 28-Jun-86 06:54:13 EDT
Reply-To: dtt@unirot.UUCP (David Temkin)
Organization: Public Access Un*x, Piscataway NJ (The Soup Kitchen)
Lines: 29

I've just started writing an arcade-style game in Lightspeed C and
there are a few problems which I'd like to clear up before moving on.

1) How do you make sure the memory for the alternate screen buffer isn't
used for something other than a display?
2) How do you tell Quickdraw to start drawing on the alternate screen
buffer? How do you switch back to the main buffer?
3) How do you make the video display hardware display the alternate
screen buffer? How can you make it do this during a vertical blank?
4) Is there a global variable I can access that holds the address of
the alternate screen buffer so that the program will run on the Mac
128, 512, and Mac Plus?

I realize that screen flipping is not a 100% Apple-approved animation
technique (and it won't run on the Lisa), but it does provide the
highest quality animation possible.

On a separate matter, has anybody found Quickdraw to be too slow for
putting down simple rectangular bit images in animation? In particular,
has anyone tried preshifted shapes (this is the old Apple II technique
where each shape is stored seven times - eight for the Mac - so
that no "bit shifting" is done when the image is put on the screen -
instead, each shape is always available in all possible bit
alignments)? Is the speed gain worth writing the assembly code it
needs?

Any help would be greatly appreciated.

David Temkin ( ...topaz!unipress!dt)