Abstract
In design and manufacturing, cavity features, such as holes and pockets, and protrusion features, such as bosses and ribs are commonly used. In this work, cavity and protrusion in a solid object were defined with the volumes enclosed by the faces of the object and their extensions. These definitions of cavity and protrusion match our intuitive notions of cavity and protrusion better than the commonly used definitions that consider the convexity and concavity of edges. Together with an algorithm called “spatial decomposition and composition”, the definitions provide a method to find cavities and protrusions in solid models. By applying graph matching commonly used in feature recognition to the volumes of cavity and protrusion, all the features in a solid model can be recognized whether they intersect or not.