Difference between revisions of "ScummVM History"

I have always been interested into understanding how games work, and got especialy interested into the scumm game engine at one point. It was possible to browse the resources using some fan-made tools, be nobody had wrote a full interpreter for those games. During holydays, in 2001, I had much time on my hand, so I decided to get going and try to write a scumm interpreter. The first step was understanding the scripts. I took a few days looking at the scripts found in MM and ZAK (I assumed it was the same engine) and understood a large bunch of opcode. Then I got into coding a tinny interpreter, making use of documentations found on the web to unpack the background graphics. This interpreter got as far as playing MM character selection screen and ZAK intro, but without any sprite/animations. I started working on this issue, and I got into interested by a document describing the sprite format used in MI2. Using this file with a little guessing, I managed to view the sprites used in MM and ZAK. For some reasons, I decided to mail the documentation author, telling him about my project and (if I remember well) asking for a few clarification (I think it was about the "layer" system). The author (Ludde) answered me quickly and told me that he was also working on a similar project. While my idea was to start with the earliest scumm version and had features as they were chronogicaly added to the original engine, Ludde was focused on MI2. I quickly realized that he was way ahead of me, as the first screenshots he showed me was a more or less working MI2 (the actual screenshots were from woodstick). I didn't had to think much before droping my own project and joining Ludde's.

I have always been interested into understanding how games work, and got especialy interested into the scumm game engine at one point. It was possible to browse the resources using some fan-made tools, be nobody had wrote a full interpreter for those games. During holydays, in 2001, I had much time on my hand, so I decided to get going and try to write a scumm interpreter. The first step was understanding the scripts. I took a few days looking at the scripts found in MM and ZAK (I assumed it was the same engine) and understood a large bunch of opcode. Then I got into coding a tinny interpreter, making use of documentations found on the web to unpack the background graphics. This interpreter got as far as playing MM character selection screen and ZAK intro, but without any sprite/animations. I started working on this issue, and I got into interested by a document describing the sprite format used in MI2. Using this file with a little guessing, I managed to view the sprites used in MM and ZAK. For some reasons, I decided to mail the documentation author, telling him about my project and (if I remember well) asking for a few clarification (I think it was about the "layer" system). The author (Ludde) answered me quickly and told me that he was also working on a similar project. While my idea was to start with the earliest scumm version and had features as they were chronogicaly added to the original engine, Ludde was focused on MI2. I quickly realized that he was way ahead of me, as the first screenshots he showed me was a more or less working MI2 (the actual screenshots were from woodstick). I didn't had to think much before droping my own project and joining Ludde's.

As stated earlier, Ludde was really ahead of me. Indeed, we had a different approach of the problem. I was implementing things by guessing and understanding how the engine was supposed to be working, and Ludde was working from disassembly. This was a great difference in term of speed and accuracy. I knew it would be better for me to change my methode in favor of Ludde's, and it ever clearer to me when I loose a large number of hours of work because of a missunderstanding. Indy4 was getting more and more playable, (but not yet completable) and I started to be interested into adding v6 games support, especialy DOTT. The thing was, the script engine had had a major facelift between v5 (MI1CD, MI2 & Indy4) and v6, so I started getting to understand that new script engine. I spent a large number of hours looking at the compiled scripts and getting to understand how they were supposed to work. When I got back to ScummVM with my newly found insight of the scumm v6 scripting system, I was faced with an already working DOTT in ScummVM. At that point, I decided to get to get into disassembly, and always make it clear to what I was working on. Even if Dott was running, it was still buggy. I remember fixing core bugs like missplaced staff text, crash on non american version (the original american version use sprites for verbs, but foreign version used plain text) and a few misc other things. Sam & Max was added to the engine not that far off but sufferend from lots of bugs. I don't keep a precise memory of that time, but I remember playtesting Sam & Max while fixing stuff here and there. The sound system in Sam & Max and a large bunch of logic script bits were very different and had to be fixed. This is also the time that Ludde (whose aim was originaly MI2/DOTT) started to loose interest in the project.

As stated earlier, Ludde was really ahead of me. Indeed, we had a different approach of the problem. I was implementing things by guessing and understanding how the engine was supposed to be working, and Ludde was working from disassembly. This was a great difference in term of speed and accuracy. I knew it would be better for me to change my methode in favor of Ludde's, and it ever clearer to me when I loose a large number of hours of work because of a missunderstanding. Indy4 was getting more and more playable, (but not yet completable) and I started to be interested into adding v6 games support, especialy DOTT. The thing was, the script engine had had a major facelift between v5 (MI1CD, MI2 & Indy4) and v6, so I started getting to understand that new script engine. I spent a large number of hours looking at the compiled scripts and getting to understand how they were supposed to work. When I got back to ScummVM with my newly found insight of the scumm v6 scripting system, I was faced with an already working DOTT in ScummVM. At that point, I decided to get to get into disassembly, and always make it clear to what I was working on. Even if Dott was running, it was still buggy. I remember fixing core bugs like missplaced staff text, crash on non american version (the original american version use sprites for verbs, but foreign version used plain text) and a few misc other things. Sam & Max was added to the engine not that far off but sufferend from lots of bugs. I don't keep a precise memory of that time, but I remember playtesting Sam & Max while fixing stuff here and there. The sound system in Sam & Max and a large bunch of logic script bits were very different and had to be fixed. This is also the time that Ludde (whose aim was originaly MI2/DOTT) started to loose interest in the project.