On the Merging of Geometric Models Based on Hierarchical Context

Abstract

Recently, efforts have been made to define the role of “context” in the Product Realization Process. This paper treats only a small slice of this problem and applies the notion of context to the automatic merging of geometric models created with the computer graphics language OpenGL. Context can be thought of as a set of properties or environmental variables of some entity that constrains or governs the behavior of that entity. The entity in this case is a three-dimensional geometric model and its context is the set of properties for viewing that model: lighting, viewing parameters, material reflective properties, colour. Now suppose a geometric model is made up of a collection of sub-models, each within its own context. If each context is associated with an integer, then the contexts can be ordered hierarchically. Thus the topmost context in the hierarchy becomes the global context for all the sub-models in the collection. Stated in another way, once a contextual hierarchy is defined, then the structure for combining these sub-models is established independently of when and in what individual contexts the sub-models are created. Consequently, context allows a concurrent generation of models within a formalized structure that automatically deals with conflict resolution — albeit in a limited way in this work. This paper describes a compiler in XML that will merge the OpenGL files automatically.