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From: snyderw@pawl17.pawl.rpi.edu (Wilson P. Snyder II)
Newsgroups: comp.sys.amiga.tech,comp.sys.amiga
Subject: Re: How to smooth scroll left?
Message-ID: <619@imagine.PAWL.RPI.EDU>
Date: 5 Apr 88 14:16:08 GMT
References: <4861@ecsvax.UUCP> <3313@csli.STANFORD.EDU>
Sender: news@imagine.PAWL.RPI.EDU
Reply-To: snyderw@pawl17.pawl.rpi.edu (Wilson P. Snyder II)
Organization: RPI Public Access Workstation Lab - Troy, NY
Lines: 30
Summary: Circular view queue?

In article <3313@csli.STANFORD.EDU> kasper@csli.UUCP (Kasper Osterbye) writes:
>I wanted to write a little game. In that little game I wanted a background
>to scroll smoothly to the left. .....
>

I may be wrong, but I believe the fastest (and easiest??) method would be
to draw the background into a wider-than-screen bit map and then change the
pointers such that the 'view' moves along the bit map, in effect creating
motion, but without memory moves.
(MemView from the Fred Fish series is a up-down example of this.)

Now, it should be possible to write the next line of data into the right
edge, and then as the screen scrolls it would come into view.  Assuming
that you do not want to save the data, the memory could 'loop arround,'
that is after X scrolls the starting address would be back at the beginning,
in effect creating a circular queue.

I used a method like this for scroling text on another system, so I have
not tried this.






______________________________________________________________________
Wilson P. Snyder II		beowulf!lunge!snyderw@steinmez.UUCP
318 Crockett Hall, RPI		(uunet!steinmez!bewulf!lunge!snyderw)
Troy, NY 12180-3590		518-276-2764, 802-658-3799 in summer
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