3D photography using shadows in dual-space geometry

A simple and inexpensive approach for extracting the three-dimensional shap e of objects is presented. It is based on 'weak structured lighting'. It re quires very little hardware besides the camera: a light source (a desk-lamp or the sun), a stick and a checkerboard. The object, illuminated by the li ght source, is placed on a stage composed of a ground plane and a back plan e; the camera faces the object. The user moves the stick in front of the li ght source, casting a moving shadow on the scene. The 3D shape of the objec t is extracted from the spatial and temporal location of the observed shado w. Experimental results are presented on five different scenes (indoor with a desk lamp and outdoor with the sun) demonstrating that the error in reco nstructing the surface is less than 0.5% of the size of the object. A mathe matical formalism is proposed that simplifies the notation and keep the alg ebra compact. A real-time implementation of the system is also presented.