Alex Paul Pentland
Local, parallel analysis of shading in an image may be used to infer surface shape without o priori knowledge about the viewed scene. The following has been proven: Given a reason- able assumption about surface smoothness, local analysis of the second derivative of image intensity allows the image-plane com- ponent of surface orientation to be determined exactly, and a maximum-likelihood estimate of the remaining depth component of orientation to be made. An algorithm has been developed to compute surface orientation, in parallel, for each image point without knowledge of scene characteristics. This algorithm has been evaluated on both natural and synthesized images, and produces a good estimate of shape.