Representation of tolerance information in solid models

A set of tolerance constraints in solid models is represented as a constraint network over the degrees of freedom of the shape elements of the body. This approach is referred to as the constraint propagation approach to the representation of tolerance information. An evaluation of the resultant constraint network provides both an analysis of a specific dimension and tolerance scheme and figures of merit regarding the combinatorial and geometric/numeric computational complexity of a set of engineering spatial constraints. This paper discusses the representation needed to achieve that evaluation. The inherent computational complexity of spatial designs can then be explicitly evaluated and controlled. For many practical cases, semantic integrity and other evaluations may be conducted in low polynomial time, in the number of tolerance constraints. The representation is applicable also to assemblies.