PHIGS

s a successor of the Core, a new proposal called Programmer’s Hierarchical Interactive Graphics Standard (PHIGS) [ANSI85] has been developed by the working group X3H31 of the American National Standards Institute (ANSI) and has been accepted as a work item by ISO in 1985. PHIGS not only provides 3D functionality but also puts some emphasis on a multilevel hierarchical data structure. This structure contains graphical output primitives, attributes and transformations which can all be edited interactively. Furthermore, substructures can be copied or referenced. By referencing other structures, a multilevel hierarchical structure can be created which is very useful if a subpicture is to occur several times on the display surface where the definition of this subpicture has been stored only once within the data structure. Attributes are stacked when executing a substructure and are restored afterwards. This all allows a higher degree of interaction compared to GKS.