Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!unmvax!uservx.afwl.af.mil!galetti
From: galetti@uservx.afwl.af.mil
Newsgroups: comp.sys.mac.programmer
Subject: Re: Can the Mac actually do animation?
Message-ID: <1991Apr9.171110.21674@uservx.afwl.af.mil>
Date: 9 Apr 91 17:11:10 GMT
References: <6205@cactus.org>
Distribution: usa
Organization: Phillips Laboratory - Kirtland AFB
Lines: 46

In article <6205@cactus.org>, rdd@cactus.org (Robert Dorsett) writes:
> In article <551@humu.NOSC.Mil>, page@humu.NOSC.Mil (Ward C. Page) writes:
>> I have been trying to do some simple animation on the Mac for a while
>> now without success.  All I want to do is move a line around the screen
>> without flicker.  The Mac can't do real double-buffering (although
>> inside Mac claims otherwise) and it can't transfer bitmaps from on
>> offscreen bitmap during the vertical retrace.  This pretty much exhausts
>> the options as far as I can tell.  There may be more approaches but the
>> Mac documentation is too poor to provide any clues.  Does anyone have
>> any suggestions or should I turn this machine into a boat anchor and
>> get some real use out of it.
> 
> I have to second the guy, a couple of weeks ago, who observed that one does 
> NOT need to do animation during the vertical retrace.  (a) it's highly 

You update the screen during the vertical retrace so there is no flicker in
your animation.  It doesn't matter how slowly you update the screen, if you
update it while it's being redrawn, part of the screen will change as you
update it, and the other part won't change until the next retrace, resulting
in a flicker.

> unlikely that the *support* logic of any animation can work faster than 60 
> times a second; (b) it's *unnecessary* to plan for 60 times a second.  Movies
> work at less than 25 Hz; most children's cartoons work at less than 8 Hz.
> Flight Simulator on the PC works at less than 20 (on a 25MHz 386).  The 
> highest-quality professional flight simulators work at 30-60 Hz.
> A lot of you seem to be losing the forest for the trees: use offscreen bitmaps 
> (1-10 smallish objects on a largely static background work best).  It'd be
> great to animate 60 times a second, but it's just not going to happen on
> any mass-market personal computer.  Animation has always been done with smoke
> and mirrors, and it probably always will.  Brute force doesn't cut it.
> 

Well, you can't really say ANY mass-market personal computer.  After all, the
Commodore Amiga easily animates at 60 Hz.  Of course, there could be some
argument as to whether the Amiga is a mass-market computer! :-)

> ---
> Robert Dorsett
> Internet: rdd@peyote.cactus.org
> UUCP: ...cs.utexas.edu!peyote.cactus.org!rdd
  ___________________________________________________________________________
 /   Ralph Galetti                  Internet:   galetti@uservx.afwl.af.mil   \
|    PL/LITT                        Interests:  computers, music, computers   |
|    Kirtland AFB, NM 87117-6008                and music, golf, sleep.       |
 \__"No, they couldn't actually prove that it was HIS vomit" - Nigel Tufnel__/