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Trying to hack Double Dragon for the NES

Started by SomeOldGuy, January 08, 2022, 09:36:03 PM

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SomeOldGuy

What's up guys!  ;D

So, got a wild hair today and decided to try and hack Double Dragon.  Everything was going OK until I edited the X axis of some of Billy's sprites.  What I found was that this change affected the enemies' sprites as well (WTF TradeWest).  Are any of y'all aware of a work around?   



Good times create weak men, weak men create hard times.  Hard times create strong men, strong men create good times...

Trax

Can you explain your actions in more details?
Did you change the sprites in real-time by modifying the data in RAM, or was it a change in the ROM?
It's possible that the code used to set sprite attributes is used for both enemies and the player.

SomeOldGuy

The sprite positions were changed in ROM.  Taking a look at the pic below, I've placed a purple border around the palette/attribute bytes, the sprite tiles have a green border, and the X/Y coordinates have an orange border.  The way they handle this info is completely different than what I'm used to seeing (RoboCop).  In my mind it should look like this:  Coordinate, Tile ID, Attribute, Coordinate and repeat.           


Good times create weak men, weak men create hard times.  Hard times create strong men, strong men create good times...

Zynk

@SomeOldGuy: Can you upload your images in other image hosting sites like imgur.com? Your posted images doesn't display at all.

Trax

It's true that Y Position, Tile Code, Attributes, X Position is the correct order for sprites as they are processed in the PPU, but it doesn't mean it shows up exactly like that in the ROM. Each game treats and stores the information differently, and not necessarily in one single neat table.

sebastianangel

Congratulations it looks great Billy! :D
I did several hacks of this game and only had problems coloring certain backgrounds since they are shared...I also had a serious bug in the cavern level that I managed to fix using the Dracula X expansion patch to MMC5. :thumbsup: