The Role of Constraints in Geometric Modelling

Abstract

Geometric constraints are important to increase expressiveness and flexibility of geometric and feature modelling. But other forms of consistency information are essential here, too, e.g., topological conditions, type constraints, etc. In many applications, overall consistency means to integrate also logical conditions. Due to the "built-in semantics" of geometry all these different forms of consistency information are not independent: they interact in various ways. Current geometrical modelling approaches do not provide the necessary expressiveness and flexibility. What is needed is an expressive and integrated way of geometric modelling. The G-Rep approach has been developed as a completely declarative, integrated approach to geometry modelling which allows a tight conceptual coupling with the various consistency representations. We describe the basic approach to declarative geometry modelling with constraints in G-Rep, and discuss some of the requirements and limitations.