Converting other games

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CTMN
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Converting other games

Post by CTMN »

How can I convert games for ScummVM that are not listed in the page of needed files in the wiki?
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eriktorbjorn
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Re: Converting other games

Post by eriktorbjorn »

CTMN wrote:How can I convert games for ScummVM that are not listed in the page of needed files in the wiki?
If you're talking about games that ScummVM claims to support, or where there is any work in progress, it really depends on which game you're asking about.

If you're asking about other games, the answer is much simpler: You can't. At all. Unless, of course, you know how to write a game engine for them, most likely from scratch. (And I'd wager that even most ScummVM developers aren't up to that task. I know I'm not.)
CTMN
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Post by CTMN »

I just don't understand how SCUMMVM works. I thought it was an emulator first... till I saw that it supports C64 roms.

And a game engine for roms?
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MusicallyInspired
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Post by MusicallyInspired »

ScummVM is a virtual machine (hence the 'VM') specifically tailored for game engines (adventure game engines, specifically) that are integrated into it. The only way to play a game in ScummVM is to reverse engineer a game's engine/interpreter and translate it into something ScummVM can interact with. This requires programming and long hard work without any compensation. ScummVM doesn't play C64 game roms, it can interpret the game files inside the ROM, because the C64 interpreter of that game was reverse engineered and integrated into ScummVM, so it can understand it.
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eriktorbjorn
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Post by eriktorbjorn »

Another way of putting it is that an emulator mimics the original hardware well enough to run the original program. ScummVM mimics the original program well enough to run the game.
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tsoliman
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Post by tsoliman »

Another analogy is flash browser games. The flash games are the "document" or "game data" or "script" or whatever you like and the flash player is the "engine". You can have a reimplementation of a flash plugin and be able to (more or less) play those games given the game data file (swf).

Another analogy is Microsoft Word. A letter/document written in word is really two pieces: the doc file itself and the word processor program. You need both to "run" the letter.
OpenOffice.org also "runs" .doc files. It doesn't emulate Microsoft Word but is a reimplementation of it. It still needs the data (the doc files) to "run" the letter/document.

ScummVM games are like that for the most part. They are all games which the developers wrote engines (script interpreters) for and had game scripts be a separate (document-like) piece. ScummVM reimplements the engines but still needs the original game data.

Some games don't have the logic in separate data files and it is sort of interwoven in the game executable itself. We call those "hardcoded" and usually won't be supported by ScummVM since it would require a rewrite of all the logic instead of just writing a logic-interpreter.

This is grossly oversimplified and inaccurate but hopefully gets the point across. :)
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LogicDeLuxe
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Post by LogicDeLuxe »

Wasn't Maniac Mansion NES the only ROM game supported? I thought, only disk version of the C64 games are supported, since there weren't any official versions on ROM.
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Post by Bobbin »

LogicDeLuxe wrote:Wasn't Maniac Mansion NES the only ROM game supported? I thought, only disk version of the C64 games are supported, since there weren't any official versions on ROM.
Without making any accusations - it's a pretty common mistake among downloaders to just call every game they download a ROM. I think there are quite a few who don't even know that games for the C64 were distributed on discs or tapes most of the time.
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MusicallyInspired
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Post by MusicallyInspired »

Doesn't even the NES MM ROM need to have the files extracted from it?
einstein95
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Post by einstein95 »

Maniac Mansion can be run from the NES rom, or have its files extracted using the tools. Either way it still works fine.
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MusicallyInspired
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Post by MusicallyInspired »

Ah.
CTMN
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Post by CTMN »

Ok thx, now I start understanding how ScummVM works.

C64 and NES ROMs don't need reverse engineering because most of them are written in assembler.

@Bobbin:

And C64 images ARE called ROMs(i'm having this nice computer and I read much on C64 forums), there are also real ROMs because the C64 has an expansion port for ROM modules(that aren't so famous as disks and tapes). I don't think that there are at all people who don't know that they use disk or tape ROMs. It depends on the emulator. Most people who use an emulator to emulate C64 games have or had a C64
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Post by Bobbin »

CTMN wrote:And C64 images ARE called ROMs(i'm having this nice computer and I read much on C64 forums), there are also real ROMs because the C64 has an expansion port for ROM modules(that aren't so famous as disks and tapes). I don't think that there are at all people who don't know that they use disk or tape ROMs. It depends on the emulator. Most people who use an emulator to emulate C64 games have or had a C64
I wouldn't call a D64 or T64 image a ROM. ROMs are either the built-in ROM chips holding the KERNAL and BASIC or the modules you put in the expansion port. Very few games were ever released as a module - see this link for a complete list.

Well, I agree that most gamers using C64 emulators had a real C64 once. It's just that I often see people asking for "Playstation roms" or "Saturn roms" - and I don't think they mean the BIOS roms ;) So I apologise for any unfair assumptions, these are just the experiences I made.

However, of course the C64 and NES versions needed reverse engineering too, it's not like the 6502 assembler language from these machines is in any way compatible with all the machines ScummVM runs on (Intel and ARM architectures).[/url]
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