Resolution of the Bas-relief ambiguity in structure-from-motion under orthographic projection

Under orthographic projection, two views of a rigid moving object are insufficient to uniquely determine the structure and motion of the object, due to the existence of the bas-relief ambiguity. Resolution of this ambiguity relies upon either prior information about the motion of the object, or else further views of the object. Two novel algorithms to resolve the bas-relief ambiguity are developed; they are well-formulated in that they minimise image-plane error, and are shown working on sequences of real images.