From: abc AT abc DOT com (riotnrrd)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Tile-based map question...... for use with Allegro
Date: Wed, 14 Jan 1998 08:27:10 GMT
Organization: Magna Data - Internet Solutions Provider
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To: djgpp AT delorie DOT com
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On Tue, 13 Jan 1998 21:46:58 -0500, <o_marciano AT ibm DOT net> wrote:

>Im am trying to create a tile based game. I am planning on using a 640x480
>resolution with a 1024x1024 virutual screen. I will scroll using the mouse.
>Even with the 1024x1024 virtual screen, that really doesnt give that much
>room to scroll around.
>
Yes, this is limited by the amount of video memory you have on your
video card.
>Recall games such as Civ2, Warcraft, CC. This games have maps that are more
>than 3-4 times the size of the physical screen (whatever the resolution may
>be). Is there some other scrolling/virtual screen technique that they are
>using to accomplish this. Or is it possible that they are using a resolution
>lower 640x480 (it doesnt seem that this is the case because everything looks
>to clear to be using a resolution such as 320x200)
You can use any resolution you want.  What you don't understand is
that these games don't store their enormous virtual screen in video
ram.  Like you said, you can only store 1024x1024.  They keep their
map off screen and copy the visible section each redraw.

If you are doing a tile based game, then you probably have an array of
tiles or something (never done a tile game myself).  To draw the
screen, you keep track of where the viewing window is relative to the
map in RAM.  Then you wait for the vsync, and copy what part of the
map is visible to the visible screen memory.  

Yes, this is a lot slower than scrolling a virtual screen, but you
simply can't get a bigger virtual screen than your video card allows.
The answer to your question is that these games _don't_ store the game
map on the virtual screen.


>
>If anyone has any knowledge on this or any suggestions at all please e-mail
>to melvins9 AT aol DOT com, as post them here as well for the rest of the public to
>see.
>
>Thanks for any responses in advance.
>
>