Use of scientific models to generate graphical virtual environments is described. In an embodiment at least two different scientific models are used. Input data which is representative of a real world environment is used by a first scientific model, such as a climate model, and data output by the first scientific model is then fed into a second, different, scientific model, such as an ecological model, in order to generate simulation data. The simulation data, which may, for example, detail the required population density of particular plant species and their size and age, is then used by a graphical simulation engine to generate a graphical virtual environment which may, for example, be used in a computer game such as a flight simulation game.