games Mercator is primarily aimed at terrain for multiplayer online games and forms one of the WorldForge core libraries. It is intended to be used as a terrain library on the client, while a subset of features are useful on the server. Mercator is designed in such a way that individual tiles can be generated on-the-fly from a very small source data set. Each tile uses a fast deterministic random number generation to ensure that identical results are produced "anytime, anywhere". This enables transmission of terrain across low bandwidth links as part of the standard data stream, or server side collision detection with the same terrain that the player sees. The use of tiles means that there is inherently a large degree of gross control of the shape of the terrain. Finer control is implemented by allowing geometric modifications - for example, a polygonal area might be flattened, or a crater could be applied.