Abstract: A method of controlling the appearance of an object in a virtual environment of a computer game, in which the computer game is arranged to move the object within the virtual environment, the method comprising: associating with the object a three-dimensional array of nodes by storing, for each node, data defining a position of that node in a coordinate system for the object; defining a first shape of the object by associating each of a first plurality of locations on the object with a respective predetermined position relative to one or more of the nodes; detecting a collision of the object with an item in the virtual environment; adjusting the position of one or more of the nodes to represent the collision, thereby adjusting the first shape of the object; and outputting an image of the object based on the adjusted first shape of the object.