Computer models are increasingly relied upon in computer games, movies, flight training and simulation for the creation of large worlds. Terrain is a vital element and, therefore, the rapid modelling of large, detailed and realistic landscapes for such worlds is an important topic in Computer Graphics. Procedural methods are used to automatically generate large terrains with a minimum input from the user. However, some control may be desirable, particularly if the user has a clear idea of the terrain appearance. An intuitive approach is to allow the user to draw some sketches and then procedurally generate terrain with features that match those sketches as closely as possible. We aim to produce realistic terrains by combining sketched curves and existing landscape data to produce terrains with features which reflect user constraint curves. This process involves the manipulation of large scale data and is thus expensive in time and resources. An important goal of this project will be the development of a distributed solution for better performance.