1. A method for modifying visibility of objects in a computer-generated scene, the method comprising: receiving, at one or more computer systems, information identifying a first object of the computer-generated scene, size and shape of the first object defined by one or more non-positional geometric properties; determining, with one or more processors associated with the one or more computer systems, a first value for at least one non-positional geometric property in the one or more non-positional geometric properties of the first object; receiving, at the one or more computer systems, information indicating an intersection between the first object and a second object in response to a computer simulation of the first object; determining, with the one or more processors associated with the one or more computer systems, a second value for the at least one non-positional geometric property in the one or more non-positional geometric properties of the first object based on an amount of interpenetration between the first object and the second object; and storing information in a storage device associated with the one or more computer systems that modifies visibility in the computer-generated scene of the first object based on the second value of the at least one non-positional geometric property of the first object.