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From: page@cod.NOSC.MIL (Ward C. Page)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Can the Mac actually do animation?
Message-ID: <2966@cod.NOSC.MIL>
Date: 4 Apr 91 03:35:43 GMT
References: <6205@cactus.org>
Followup-To: page@cod.nosc.mil
Distribution: usa
Organization: Naval Ocean Systems Center, San Diego
Lines: 51

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. 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 
>unlikely that the *support* logic of any animation can work faster than 60 
>times a second; 

I'm getting about 100Hz update on the simple symbology that I'm moving
around the screen.  The problem is not with the update rate but with the 
flicker caused by rewriting the screen a couple times per frame.  If you
can't draw during the retrace then your not really doing animation.  Your
just flailing away at the screen.  Control of the update rate is 
important in animation, and it's done by syncing with the screen refresh
somehow.  Normally, this is done with a double buffered system.


>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.

Movies have the advantage of motion blur which reduces the need for faster
updates (movies run at 24 fps and video at 30 fps).  Flight simulator on
the PC is really to slow to get any real feel for flying.  This is why the
high dollar flight simulators run at at least 50 Hz for regular flying
tasks, and upawrds of 100-120 Hz for any handling qualities work.

>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.
>

This is true,  but the hardware is thre for getting impressive performance
out of the machine i fonly the utilities had been a little better thought
out.  For the 10,000 bucks we spent on this Mac II fx we could have bought
a couple of SGI Iris 3D's.  I guess I was expecting too much of Apple.


>Robert Dorsett


Ward Page
Naval Ocean Systems Center
(formerly General Dynamics Flight Simulation Lab)