1. A hierarchical bottom-up method of construction and storage of a hierarchical computer graphics data set, the method comprising: combining at least two base data objects into at least one combined data object, simplifying each one of said at least one combined data object into a simplified combined data object, said simplified combined data object having a reduced memory size with respect to said combined data object, storing each one of said simplified combined data objects, and storing first data identifying the base data objects used to generate each combined data object and transformations applied to the base data objects to generate each combined data object, combining at least two simplified combined data objects into at least one higher order combined data object, simplifying each one of said at least one higher order combined data object into a simplified higher order combined data object, said simplified higher order combined data object having a reduced memory size with respect to said higher order combined data object, storing each one of said simplified higher order combined data object, and storing second data identifying simplified combined data objects used to generate each higher order combined data object and transformations applied to the simplified combined data objects to generate each higher order combined data object, wherein the step of simplifying combined data objects and the step of simplifying higher order combined data objects are carried out automatically by a computer.