A modder has revealed how Rockstar Games fit Grand Theft Auto III's open world into the PlayStation 2's 32 MB of RDRAM. The game's 4-kilometer-wide Liberty City could not load entirely into memory at once.
Streaming system loads assets on the fly
Game Maker's Toolkit created a modded executable that shows the game's streaming system in real time. As the player moves, assets are loaded from the DVD and unloaded behind them. The total asset size is around 130 MB, far exceeding the console's memory.
Former GTA III programmer Obbe Vermeij said that streaming was the hardest technical challenge during development. The code was written by Adam Fowler. The map is split into three islands, each further divided into sectors that load and unload as needed.
Mark Brown of Game Maker's Toolkit explained that Rockstar built a moving window that shows just enough of the city to make the illusion work. The game secretly builds the world in front of the player and deletes it behind them.
Source: NotebookCheck
