Representation, evaluation and editing of feature-based and constraint-based design.

摘要

This thesis investigates a general and systematic approach to feature-based and constraint-based design. We combine feature-based design and constraint-based design by globally decomposing a design into a sequence of feature attachments and locally defining and positioning each feature by constraints. Analogous to the concept of high-level programming languages, we formalize a layered design model that eliminates the dependency of a design representation on a solid modeler. With this design model, design intent, such as feature descriptions and constraints, is stored in an unevaluated, modeler-independent design representation while the geometry to which it corresponds is stored in an evaluated, modeler-dependent design representation. The separation essentially relies on a naming and matching schema that converts between a geometric reference and a generic name, and a design compiler that automatically instantiates the unevaluated design representation to an evaluated design representation with respect to a solid modeler.;The geometric references for defining feature attributes and constraints are recorded with their generic names in the unevaluated design representation. We propose several techniques for naming geometric entities unambiguously.;The design compilation or instantiation involves remapping a generic name back to a geometric reference in the selected geometric modeler, solving constraints and implementing feature operations or attachments. Instead of developing a constraint solver for this design compiler, we use an independent and general solver. Feature attachment operations are different from classical Boolean operations in solid modeling. However, we provide a semantics for them that is based on existing operations in solid modeling.;The layered design model allows users to edit archived conceptual designs to derive new designs quickly. We investigate the coordination of later features in the unevaluated and modeler-independent representation when a feature is edited and provide a method for editing feature-based and constraint-based design.;We also discuss how to extend this work to a commercial feature-based and constraint-based CAD system.