Radiosity is a method of rendering an image using only visible light sources, and calculating all the paths that light will take from these sources to illuminate a scene, taking into account the fact that light bounces off objects multiple times. In traditional 3D games, light reflection was only calculated once, and as a result interior areas often had to "cheat" by placing invisible fill lights inside rooms in order for the player to see anything. However, as brightness decreases drastically with every bounce off a wall, without HDR techniques the light streaming in from an outside source would never be bright enough to fill a room. In addition, when using radiosity it becomes possible to simulate the behavior of light when it passes through translucent media, such as the effect when light streams through stained glass windows.

It takes a server farm of 32 computers about 40 minutes to compile The Lost Coast level.