A procedure for automatically correcting invalid flat triangles occurring in triangulated contour data

Abstract

Constrained Delaunay triangulation is used widely as a basis for triangulating contour data. However, this method frequently produces triangulations that include flat triangles (i.e. where the three vertices of a triangle lie on the same contour). In many situations, such triangles fail to reflect the true shape of the surface being modelled. This paper presents details of a procedure, termed flat triangle corrector, which automatically corrects invalid flat triangles and produces a more accurate surface approximation. A detailed description of the procedure is provided in the form of a commentary and pseudo-code listing. Experimental results on digitised contour data demonstrate that the approach is successful in correcting all flat triangles in a series of triangulations.