[stella] Playfield ram usage

Subject: [stella] Playfield ram usage
From: "Glenn Saunders" <cybpunks@xxxxxxxxxxx>
Date: Tue, 21 Aug 2001 16:35:09 -0700
All this talk about Arkanoid and RAM usage has me thinking more and more about my Death Race game and the strategies in saving RAM there.

I'm only using PF1 and PF2 so that means 32 bits per row and I'd like to have about 23 or so rows, about 8 pixels tall, which brings me up to about 100 bytes RAM usage. When I add in all the rest of the gamestate, which is 4 X/Y positions, the score, etc... that doesn't leave much breathing room.

The thing is, I will never fill up the entire screen with tombstones.

If I know, for instance, that I will never have more than 32 tombstones, then I could store it in 32 bytes as a list of tombstones, the value of which is an index to a pixel.

The problem is having to convert these indexes on the fly during the kernel. Assuming the list is sorted, it needs to scan through them in a loop, then convert a number to a bit in a playfield register to turn on, then continue the loop, turn on another bit if necessary, etc...

I don't think this can be done on the fly without sacrificing sprite logic on those scanlines, and while I'm not going to reposition the players, I do intend to alter the missiles.

Is there some way to do this in self-modifying code in RAM?

GLENN SAUNDERS===============================
By Day - Web Developer - http://www.eUniverse.com
By Night - Producer - Cyberpunks Entertainment
Personal homepage: http://www.geocities.com/Hollywood/1698
Cyberpunks Entertainment: http://cyberpunks.uni.cc

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