Reconstruction of Lambertian surfaces by discrete equal height contours and regions propagation (original) (raw)

This paper describes two new methods for the reconstruction of discrete surfaces from shading images. Both approaches are based on the reconstruction of a discrete surface by mixing photometric and geometric techniques. The processing of photometric information is based on reflectance maps, which are classic tools of Shape from Shading. The geometric features are extracted from the discrete surface and propagated along the surface. The propagation is based in one case on equal height discrete contour propagation and in the other case on region propagation. Both methods allow photometric stereo. Results of reconstruction from synthetic and real images are presented. q † The global minimization approaches, the principle of which is to minimize a global energy function. Usually this energy measures a difference between the image intensity and the intensity calculated from the reconstructed surface. Additional constraints like smoothness or integrability of the surface are often used (see, e.g. Ikeuchi and Horn , and Frankot and Chellappa [3]). † The local derivative approaches, the principle of which is to try to recover the shape information from the intensity image and its derivatives. For example Lee and Rosenfeld [10] compute the normal vector to the surface by using the first derivative of the intensity. † The linear approaches used the linear approximation of the reflectance function (see Pentland [11] or Tsai and Shah [17]). † The propagation approaches, which consist in propagating shape information from singular points. The first shape from shading technique introduced by Horn was a propagation approach with a reconstruction based on the extension of characteristic strips .