Representing dimensions, tolerances, and features in MCAE systems

A method is presented for explicitly representing dimensions, tolerances, and geometric features in solid models. The method combines CSG and boundary representations in a graph structure called an object graph. Dimensions are represented by a relative position operator. The method can automatically translate changes in dimensional values into corresponding changes in geometry and topology. The representation provides an important foundation for higher-level application programs to automate tolerance analysis and synthesis. The implementation of a prototype interactive polyhedral modeler based on this representation is presented.<>