This paper clarifies a sufficient condition for the reconstruction of an object from its shadows. The objects considered are finite closed convex regions in three-dimensional Euclidean space. First we show a negative result that a series of shadows measured using a camera moving along a circle on a plane is insufficient for the full reconstruction of an object even if the object is convex.Then, we show a positive result that a series of pairs of shadows measured using a general stereo system with some geometrical assumptions is sufficient for full reconstruction of a convex object. Furthermore, we show that a class of non-convex objects, which we define as slice convex objects, are also reconstractable from a series of shadows.
