Meta-attributes for Graphics Collection Classes

Abstract

Graphics systems such as GKS, PHIGS, or GEO++ differ mainly in how graphics entities can be grouped into collections and how attributes can be assigned to them. In PHIGS, sequential structures are provided to build up multi-level hierarchies; GKS offers a single-level segment concept; GEO++ supports a set-oriented approach to handle part hierarchies. Besides the concept for collecting graphics primitives, the predominant structuring concept, additional constructs are used to filter out, select, or group specific subsets of the whole set of graphics objects. In PHIGS, the concept of name-sets allows assignment of a set of names to any primitive in order definition of filters for each of the three types of attributes, visibility, highlighting and detectability. GEO++ allows to define ad-hoc sets by using object identifiers for parts. In GKS-R, the revised version of GKS, name-sets are introduced as primary construct to assign attributes to output primitives. In this paper we introduce basic mechanisms for collecting graphics entities and for assigning attributes. These mechanisms are defined on a meta-level allowing us to extend a low-level kernel and to interpret systems such as PHIGS, GKS-R, or GEO++ as special cases of one flexible system.