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Topic: Mega Man 3 (possibly just general) ROM offset question (Read 2 times)
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trevbot
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« on: September 21, 2008, 09:43:30 am » |
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I was wondering if there was a particular way to go about figuring out the ROM map. Is it just a trial and error type of thing? Is there anyone out there with specific knowledge of how the MM3 ROM is laid out?
I wonder this because there are a few things I'd like to try to remove, such as the automatic scrolling foregound/background effect in Gemini Man's stage, which I assume is hard-coded somewhere. Matrixz was able to point this kind of info out when it came to a similar problem in a different stage, I wondered if it would be a particularly difficult undertaking to learn how to find these kinds of things on my own.
Any input?
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Disch
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« Reply #1 on: September 21, 2008, 07:17:33 pm » |
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I know a guy on IRC (kuja_killer) who is ripping this game apart. I'll see if I can point him towards this thread.
Stay tuned
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kuja killer
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« Reply #2 on: September 21, 2008, 10:31:45 pm » |
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To stop the scrolling and stars thing of gemini man:
$3C9D4 & $3C9D8 ..change both of those to something other than 00-11 ..just put them to FF if you never want to use it in the whole game.
But if you do want to for a stage beside gemini..then you put the stage id value there.
00 = needle, 01 = magnet, 02 = gemini, 03 = hard...etc etc
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Jigglysaint
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« Reply #3 on: September 21, 2008, 10:54:09 pm » |
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I know a guy on IRC (kuja_killer) who is ripping this game apart. I'll see if I can point him towards this thread.
Stay tuned
Speaking of IRC, I haven't been able to log in. Same server? Same channel? Rom-hacking that is. |
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Dragonsbrethren
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« Reply #4 on: September 21, 2008, 10:55:55 pm » |
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Speaking of the stars in Gemini Man's stage, is there any reason they didn't use all three screens they had set up for them? It would've been cool seeing that planet scroll by, as it is now you can only have it on the first screen and it looks pretty lame when it scrolls of the left side and immediately reappears on the right. I got around this when I was working on a hack by having a second outside area later in the stage where you got to see the planet, that graphic is too cool to go to waste.
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kuja killer
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« Reply #5 on: September 21, 2008, 11:00:33 pm » |
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Well i wouldn't know why capcom didn't do it. But reason why it'll reppear on the right side of the screen is because that effect is done through IRQ's, and anything above the division line between the normal playfield, and the scrolling irq effect will cause that part of the screen to never draw anything. It'll only keep the contents of the screen when it was first loaded, and never do anything with it from there on. But the game does have some bits of code in the screen drawing routines that stops the drawing of the screen above the line, if it were removed, then the screen WOULD continue to draw normally, but it will never look proper or correct reguardless, and that can not be helped. NES limitations.  |
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Dragonsbrethren
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« Reply #6 on: September 21, 2008, 11:04:10 pm » |
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I figured as much, thanks for confirming.
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Disch
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« Reply #7 on: September 21, 2008, 11:39:55 pm » |
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#rom-hacking on irc.esper.net (not affiliated with this site in any way)
#ROMHacking.net on irc.darkmyst.org (which I guess is this site's IRC channel, but I don't often go there)
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Kajitani-Eizan
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« Reply #8 on: September 22, 2008, 06:32:32 am » |
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wait, what planet? i don't remember, and youtube videos don't seem to show anything like that...
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KingMike
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« Reply #9 on: September 22, 2008, 09:13:38 am » |
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There are some magazine scans of a prototype version of the game that had a planet in the background. Thank you Google Images  |
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Dragonsbrethren
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« Reply #10 on: September 22, 2008, 09:49:12 am » |
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It's still there in the final, it's on the second screen of the stage but only the blocks from the first screen are used for the parallax effect.  The planet glows and the ring spins--one piece of the ring uses the wrong palette by default though, which is easily fixed. The planet graphics can be added to the first screen and you'll see it scroll along with the stars. |
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trevbot
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« Reply #11 on: September 28, 2008, 12:22:20 pm » |
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So, um, even though that is a cool graphic... no one seems to have answered the original question, which was: Is there any sort of method to figuring out the ROM map, or am I basically stuck with trial and error?
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kuja killer
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« Reply #12 on: September 29, 2008, 01:05:52 am » |
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http://www.romhacking.net/docs/mmlevfrm.txtWell this will explain the level format at least which is always located at A10+2000 for each level. needleman level data at $A10 ... magnet at 2A10.. gemini at 4A10 ..etc. all the way up to $26000 The first A0F bytes of every 2000 is game code for various things in the game like the pause menu, sprite palletes, wily/light scenes, etc. I dont exactly really have any document(s) specifically of a ROM map of the game although i know what everything in the game is, because in my hack i've moved every single last possible bank of code to other areas of the rom, so they don't match up whatsoever with an original rom.
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Disch
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« Reply #13 on: September 29, 2008, 08:39:25 pm » |
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kuja: I don't think he was asking for a ROM map... he was asking how do you MAKE a ROM map.
To answer that, the only real way I know of is to either corrupt sections until you figure out what they do, or do a full disassembly
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Dragonsbrethren
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« Reply #14 on: September 30, 2008, 06:35:28 am » |
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Pattern recognition and a little luck works too, I've found quite a bit of data that way.
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« Last Edit: September 30, 2008, 07:14:51 am by Dragonsbrethren »
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