GTA: Liberty City is one of the most impressive mods for GTA: Vice City. It can even be considered a game of its own. It a community project aimed to bring the city from GTA 3 (Liberty City) onto GTA: Vice City engine. With all the new features of Vice City, such as bikes, helicopter and graphic optimizations, GTA: Liberty City is a GTA 3 experienced in a totally new way.
The projects main hub is at GTAForums where you can follow the latest developments and download the latest version of the mod.
Here are my contributions to Liberty City project.
Liberty City Launcher
While Rockstar tried to make GTA: Vice City mod-friendly, there are still a lot of features which are hardcoded in the executable and need to be modified for the project to work properly. Be it the limits that need expanding, the front-end appearance, the mission script, the goal is to make Vice City look and behave exactly as GTA 3. The launcher's job is to make hardcoded boundaries disappear.
Vice City Opcode Enabler
To play the missions, GTA has a built-in interpreter which reads the commands one-by-one from the file main.scm and executes them. Unfortunately, a lot of commands which were used in GTA 3 mission script are no longer supported by Vice City. To walk around this problem, I created a framework with which it is possible to add new commands which Vice City interpreter can understand, provided that the programmer has some knowledge of assembler and memory layout of the game.
The binary dynamic-link library which is automatically loaded when Vice City loads is found in the main archive of the GTA: LC Launcher.
Vice City Opcode Enabling Framework Source (62 KB, last updated June 26, 2006).
The character models of GTA VC underwent considerable change compared to the models of GTA 3. In GTA 3, models consisted of small body parts each of which were deformed as the time in the cutscene went by. Character models in GTA VC have one whole body, which is supported underneath by a skeletal bone structure. The transformations are performed on bones and reflect on the body which produces a more realistic animation. Although the format of cutscenes stayed the same between games, making it possible to directly use it in GTA VC, the transformations defined on the character models of GTA 3 produced non-sense results on GTA VC when applied to GTA VC models. Cutscene converter is a quick and dirty converter of GTA 3 cutscenes to GTA VC.
It can also be used as a cutscene editor, but because it was mainly designed for conversion, the user interface is very uncomfortable.