Path: utzoo!utgpu!water!watmath!clyde!att!ucbvax!XEROX.COM!"Robert_L._White.ESXC15"
From: "Robert_L._White.ESXC15"@XEROX.COM
Newsgroups: comp.sys.atari.st
Subject: ANIMATION QUESTION
Message-ID: <880831-204234-3799@Xerox>
Date: 31 Aug 88 16:37:47 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 34

I have been playing around with graphics lately and have some questions about
animation.  Someone tell me if I am figuring this out right. 
Since the screen is redrawn every 60th of a second, and I was to move a 
Line A sprite 1 pixel at a time, this would give me a movement of 60 pixels
per second, right?  Thus it would take about 5.3 seconds to move accross
a low resolution screen, Right???

My question here is, How do I make the sprite move faster than 60 pixels
per second? Is it possible?  I have tried moving the sprite 2 pixels at a time,
But then the sprite seems to be a little jirky or blurry.  I have looked at some
games, and some of them seem to be able to move images faster than this
without the blurr.
How do they do it? What are some of the tricks?

The way I am doing my animation is this. I am using 3 screens.  One holds the
background picture, one is the drawing screen (LOG BASE), and one is the 
screen being viewed (PHYS BASE).
For 1 animation sequence I copy the background screen to the LOG BASE
screen, then draw my sprite to the LOG BASE screen, Then do a 
SETSCREEN to swap the  PHYS BASE screen with the LOG BASE screen.
Thus the old PHYS BASE screen becomes the new LOG BASE screen and the old LOG
BASE screen becomes the new PHYS BASE screen.
This is then repeated every vertical blank, and every thing works great, 
with no flicker (at 1 pixel per Vertical blank).

I am writing my code in 'C' and assembly.  The background screen copy
routine is in assembly (for speed), and the rest is in 'C'.   I am pretty sure I
am doing all my animation  before the Vertical blank, and am executing the
SETSCREEN command every vertical blank, (60 setscreens per second). 
I  have verified this because I seem to be able to move 60 pixels per second.
If anyone can give me some tips  on how to move a sprite faster, it would 
be appreciated.
Thanks, 
Robert L. White, Xerox Corp.