Before revision:  For such data sets, one must first classify their images into homogeneous groups , where each group corresponds to the same underlying structure , followed by reconstruction of a three-dimensional model from each of the homogeneous groups.
After revision:  For such data sets, the algorithms must include some classification procedure to identify homogeneous groups within the data, so that the images in each group correspond to the same underlying structure , followed by reconstruction of a three-dimensional model from each of the homogeneous groups.