Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!euler!amorando
From: amorando@euler.uucp (Alex Morando)
Newsgroups: comp.sys.amiga.tech
Subject: Re: large scrolling areas, as in a game
Message-ID: <26353@ucbvax.BERKELEY.EDU>
Date: 6 Oct 88 23:32:58 GMT
References: <1214@astroatc.UUCP>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: amorando@euler.UUCP (Alex Morando)
Organization: U.C. Berkeley EECS CAD Group
Lines: 29

In article <1214@astroatc.UUCP> jojo@astroatc.UUCP (Jon Wesener) writes:
>
>    I'm trying to create a long continuous display that can scroll left to
>right as done in many arcade games.  Thing is, I think I'm limited to a
>width of 1024 pixels in which I figure I can fit about 3 screens worth
>of data.  

You should tell us why you are limited to 1024 pixels, as I myself cannot
see any such limitation.

My idea is:

Do not have a huge bitmap. Only have a normal sized one, say 320x200. At
the bottom have as many extra lines as you want screens, say 10. SO: in
memory you have a 320x210 pixel bitmap.

To do the horizontal scrolling, update the bitmap pointers one word at
a time, thus pushing the display to the right. For each new word, write in
an entire column of new data one word wide. Do the same for scrolling left.
THere could be trouble if you want the display to wrap around.

So what happens is, after 20 words are shifted in, the display is now
displaying the same bitmap, but one line down, and the whole bitmap has
been updated to new stuff. Horizontal scrolling is thus very simple and
does not use a lot of memory.

David Ashley
amorando@euler.berkeley.edu
Guest on this new account.