This paper presents a new algorithm for reconstruction of a 3-dimensional object using silhouettes subtracted from 2-dimensional photos. The basic idea is to shoot a series of photos around a 3-dimensional object from different angles

subtract the boundaries of the object from the photos

and then combine the 2-dimensional information by tracing the rays to obtain the 3-dimensional coordinates of the points on the approximation surface of the object. Compare to some available method based on the concept of "voxel"

our algorithm has the following advantages:(1)It significantly saves space because only the 2|dimentional mask boundaries need to be saved in memory; (2)The accuracy of approximation is independent of the 3-dimensional resolution since we are not using voxels; and 3. the speed is also greatly improved especially when the object has large volume since instead of projecting every voxel

only the points on the surface are computed according to our method.