An Algorithm for Grouping Lines Which Converge to Vanishing Points in Perspective Sketches of Polyhedra

We seek to detect the vanishing points implied by design sketches of engineering products. Adapting previous ap- proaches, developed in computer vision for analysis of vectorised photographic images, is unsatisfactory, as they do not allow for the inherent imperfection of sketches. Human perception seems not to be disturbed by such imperfections. Hence, we have de- signed and implemented a vanishing point detection algorithm which mimics the human perception process and tested it with perspective line drawings derived from engineering sketches of polyhedral objects. The new algorithm is fast, easily- implemented, returns the approximate locations of the main vanishing points and identifies those groups of lines in 2D which correspond to groups of parallel edges in the 3D object