easiest emulator to modify?

Petruza · Post by **Petruza** » Sat Jan 10, 2009 10:50 pm

Hi, I'd like to make some tools to debug and reverse-engineer the NES.
So I don't want to have a hard time trying to understand and even compile a complex emulator.
So in your experience, what emulator would you think is the easiest one to have a look at its source, understand it and compile it with some modifications?
It doesn't matter if its emulation isn't 100% accurate, as long as works fine.
Using SDL is a plus, as I'm already familiar with it.
Also an emulator whose source code doesn't have to be modified in order to run on windows would be really nice.

Thanks!

Dwedit · Post by **Dwedit** » Sat Jan 10, 2009 11:16 pm

If you want to see source code to better understand how the NES works, and troubleshoot issues in your own emulator, look at the source code to Nintendulator.
Its PPU code is a great reference to what events happen on which PPU cycle.

Petruza · Post by **Petruza** » Sun Jan 11, 2009 7:03 am

Well, I don't just want to understand how the NES works, yes that's the main reason, but actually I want to be able to compile and run the emulator and try to make some changes to its source and see them running.
I've seen really cryptic code in many open source projects.

Thanks, I'll give it a try!

MottZilla · Post by **MottZilla** » Sun Jan 11, 2009 11:48 am

What kind of modifications are you looking to do?

Dwedit · Post by **Dwedit** » Sun Jan 11, 2009 1:08 pm

Hardest emulator to modify: FCEU

Petruza · Post by **Petruza** » Sun Jan 11, 2009 3:36 pm

MottZilla wrote:What kind of modifications are you looking to do?

Some that come to mind now:
- sprite inspector: specify a sprite index so that the emulator draws a colored squate around it so you can identify it.
The idea that motivated this is based on Pacify3D, which emulates the arcade port of Pacman, rendering the characters in 3D while the emulation runs.
I'd like to make an emulator that can recognize sprites and render them in a 3D space, witrh predefined 3D models of course. So you can make a file which specifies 3d models and textures to certain sprite indexes, or certain pixel patterns, or palettes, or whatever.

I've debugged some games, and noted that, for example, Super Mario Bros has static CHR ( most likely ROM ) while Kirby's adventure modifies some tiles in run-time to make the wave effect in the water, and I wonder if mario or kirby are always the same sprites, say 0,1,2 and 3, and they vary their tiles throughout the game, or not...

So far that's the only feature I would like to have in order to get a better idea of how commercial games handle sprites, but I'm sure I'll think of some other usefull features as well as you can sugest some to me

Dwedit wrote:Hardest emulator to modify: FCEU

I kinda figuered that out