
Accession Number : ADP001193
Title : Surface Constraints from Linear Extents,
Corporate Author : COLUMBIA UNIV NEW YORK DEPT OF COMPUTER SCIENCE
Personal Author(s) : Kender,John R.
Report Date : JUN 1983
Pagination or Media Count : 5
Abstract : This paper demonstrates how image features of linear extent (lengths and spacing) generate nearly imageindependent constraints on underlying surface orientations. General constraints are derived from the shapefromtexture paradigm; then, certain special cases are shown to be especially useful. Under orthography, the assumption that two extents are equal is shown to be identical to the assumption that an image angle is a right angle (i.e. orthographic extent is a form of slope or skewed symmetry). Under perspective, if image extents are assumed equal and parallel, extent again degenerates into slope. In the general perspective case, the shape constraints are usually complex fourthorder equations, but they often simplifyeven to graphic constructions in the image space itself. If image extents are colinear and assumed equal, the constraint equations reduce to second order, with several graphic analogs. If extents ae adjacent as well, the equations are first order and the derived construction (the jackknife method) is particularly straightforward and general. This method works not only on measures of extent per texel, but also on reciprocal measures: texels per extent. Several examples and discussion indicate that the methods are robust, deriving surface information cheaply, without search, where other methods must fail. (Author)
Descriptors : *Images, *Surfaces, *Linearity, Three dimensional, Cueing, Lines(Geometry), Points(Mathematics), Angles
Distribution Statement : APPROVED FOR PUBLIC RELEASE