Estimation of illuminant direction, albedo, and shape from shading

A robust approach to recovery of shape from shading information is presented. Assuming uniform albedo and Lambertian surface for the imaging model, we first present methods for the estimation of illuminant direction and surface albedo. The illuminant azimuth is estimated by averaging local estimates. The illuminant elevation and surface albedo are estimated from image statistics. Using the estimated reflectance map parameters, we then compute the surface shape using a new procedure, which implements the smoothness constraint by enforcing the gradients of reconstructed intensity to be close to the gradients of the input image. Typical results on real images are given to illustrate the usefulness of our approach.