An Integrated Approach to Geometric Modeling

Solid modeling has been recognized as a powerful computer -aided design tool, being informationally complete and semantically well-formed. However, it is insufficient by itself to support the design process of complex artifacts such as buildings , since it lacks the abstraction properties provided by computer-aided drafting tools. This paper presents an integrated approach to geometric modeling that combines the power of solid modeling with the intuitive design and communication capabilities of drafting. Integration is achieved by representing the designed artifact non-redundantly in a 3-dimensional WORLD , and manipulating it through multiple 2-dimensional VIEWs. The WORLD consists of a collection of shapes that store all the formative information pertinent to the designed artifact, while the VIEWs consist of images of selected shapes, generated through particular two-way mapping transforms. Simultaneous display of several VIEWs that depict the same set of shapes through different transforms enables addressability of points in the 3-dimensional WORLD. The shapes are represented by a data structure based on the hybrid edge model, which facilitates the integration of points, lines , polygons, and solids in one formative hierarchy. VIEWs reference the formative entities in the database, and include design and communication aids (e.g. dimension lines, construction lines, annotations and graphic symbols) to enhance the visual content of the images without encumbering the representation of the shapes themselves. Modifications that are applied to the shapes through any VIEW are immediately apparent in all other VIEWs in which the shapes are imaged. The integration of drafting and modeling simplifies the use of powerful modeling utilities by designers, facilitates communicating the results of the design process, and enhances the integrity of the designed artifact.