Structure from stereo and motion

Stereopsis and motion parallax are two methods for recovering three-dimensional (3D) shapes. Theoretical analyses of each method show that neither alone can recover rigid 3D shapes correctly unless other information, such as perspective and vertical disparity, is included. The solutions for recovering rigid structure from motion have a reflection ambiguity; the depth scale of the stereoscopic solution will not be known unless the fixation distance is specified in units of interpupil separation. (Hence the configuration will appear distorted.) However, the correct configuration and disposition of a rigid 3D shape can be recovered if stereopsis and motion are integrated, for then a unique solution follows from a set of linear equations. The correct interpretation requires only three points and two stereo views.