Visual recognition of CAD objects with aspect graphs
The authors analyze how the geometrical model of objects from a CAD system can be used to build exactly a new representation of these objects that is better suited for visual recognition. A 3-D object has in general an infinite number of different 2-D images, depending on the viewpoint. Its image contours have, however, only a finite number of different topological aspects. An aspect graph is a graph in which the nodes are the stable aspects, and the arcs are the visual events that make the image contours switch from one stable aspect to another. It is shown how to compute exact aspect graphs of general CAD objects under perspective projection using results obtained here and algorithms from real algebraic geometry.<<ETX>>