Revision of Inconsistent Orthographic Views

T. Watanabe

Journal for geometry and graphics, Tome 2 (1998) no. 1, pp. 045-054.

Résumé

Many algorithms for the generation of solid objects from two-dimensional (2D) orthographic views have bottom-up procedures which generate 3D segments, form 3D faces and construct polyhedrons. When they accept a set of consistent view drawings, they present at least one solid object. However, when the input views are not consistent, contradictions appear during the process in each step of the bottom-up approach. We examine incoherences found in each step of the bottom-up approach in these cases. Then we introduce a method which reveals the sources of incoherences in input views and suggests consistent views. Three kind of sources are considered: extra segments, improper designations of line types (visible lines or hidden lines) and missing segments. Extra segments and improper designations of line types are found by projecting the solid object constructed from subset of 2D segments onto view planes. Probable missing 3D segments are generated not from three views but from two views among three views. Some heuristic rules are proposed in order to select more probable missing segments and make the process efficient. The present method can be used to detect operator's mistakes in input views or misunderstandings of drawing recognition systems.