A variable resolution graph based model of three dimensional objects

A hierarchical boundary model of three dimensional objects provides a representation of the surfaces enclosing it at successively finer levels of specification. A hierarchical graph structure for encoding the boundary of a solid object at variable resolution is described. This model, called structured edge-face graph, is based on a face oriented relational description of the object boundary. In the paper, the concept of variable resolution surface representation is briefly reviewed, and the structured edge-face is described in detail. A data structure for encoding a structured edge-faced graph is presented. The concept of adjacency relation between pairs of primitive boundary entities at fixed accuracy is introduced, and adjacency finding algorithms, which operate on a structured edge-face graph object representation, are presented. Four basic operations for defining and manipulating a structured model are described. These primitives support both a bottom-up and a top-down development of the hierarchical boundary model.