Constraint-based virtual solid modeling

Constraint-based solid modeling is the kernel part of current CAD systems. It has been widely used in supporting detailed design and variational design. However, it cannot support early stage design and is not easy-to-use because it demands fully detailed input description of a design. To solve these problems, researchers attempt to incorporate virtual reality techniques into geometric modeling systems. This paper presents a novel approach for interactive constraint-based solid modeling in a virtual reality environment. The approach allows the designer to construct and edit a constraint-based solid model by direct 3D manipulations, and ensures the created solid model to be precise by recognizing and solving geometric constraints. To effectively support 3D manipulations and change propagation, a new constraint-based solid model is adopted. In the model, besides the normal constituents of the typical constraint-based solid model, some new attributes like shape control points, location pattern and explicit shape constraints of a primitive are defined. Guided by the location pattern, our algorithms for recognizing and solving location constraints are real-time.