View Single Post
Old 08-08-2019, 11:49 PM   #3
Junior Member
Eskayelle's Avatar
Join Date: Jun 2017
Posts: 16

Thanks for the tips! The hex code comes from a tutorial on how to hack portraits, that tutorial using Pancake 2 to decompress the portrait titles once the offset is entered, and then SonMapEd used to map the tiles so the replacement can mimic it. I was trying to "reverse engineer" it to place a title screen in ROM. I don't have a disassembly, so I was going to do searches in the hex for matching bytes and verify I had the right routine based on the title screen offset being nearby, once I located a title screen offset.

For reference, the tutorial is here:

To my knowledge, the title screen's compressed. Most of the sprites are, as are the portraits.

I used the r57 shell mod for Gens (debugger) and was able to see the title screen in VDP RAM.

Snippit of VDP RAM:

I dumped the RAM and attempted to do a search on a snippit of it in the ROM using HxD. No luck. Tried another. Same. I'm thinking it likely is compressed.

I was able to dump the palette in VDP RAM and match that in the ROM, so I think the title screen palette is at $5D74.

I figured I'd try to use a disassembly with a breakpoint on the $5D74 value to perhaps find the decompression scheme or a table with the title screen offset. The game breaks at $18E6, right before the title screen comes up, so I feel like I'm in the right place. The command at $1836 is move.w (A6)+,D4, where A6 appears to be represented by $5D74. I'm not familiar with 68k assembly, so I'm not sure yet how to interpret it.

Snippit is here, for reference:

In the meantime, I'm trying to set up my hack to put shadows on sprites. It's quite a pain, so I figured in the meantime, if I could, I'd try to see if a new title screen were viable, hence the thread.
Eskayelle is offline   Reply With Quote