<title>Three steps to make shape from shading work consistently on real scenes</title>

Abstract

For a long time shape from shading had problems to work on real scenes. It was formulated with too simplified physical models which made its application to real scenes difficult and the integration with other modules inconsistent because the physical models of the other modules were more complex and different. These limiting physical models have been: the orthogonal projection, the restriction to a light source at infinity and the lambertian diffusion mode. It also could only calculate either depth or photometric characteristics. One of them had to be known, which is a priori difficult for real scenes. This work present shape from shading in a general formulation using more complex physical models which can cope with the complexity of real scenes and which are consistent with other modules. The physical models are: the perspective projection, point light sources and ambient light as well as the Phong's reflection model dealing with diffuse and specular reflection. In order to overcome the problem of the shape from shading module to be ill-posed and to calculate consistently both depth and photometric characteristics at the same time we use stereo photometry and the cooperation with stereo vision.