1. An apparatus comprising: an obtaining unit configured to obtain a range image which indicates distance information to a target object, which is captured by an image capturing unit; a coarse position/orientation obtaining unit configured to obtain a coarse position and orientation of the target object; an estimation unit configured to estimate a variation degree of distance information on a region of the range image, wherein the region corresponds to a predetermined region on a shape model of the target object; a selection unit configured to select, for each predetermined region on the shape model, sample points from the predetermined region in accordance with the estimated variation degree, so as to reduce the number of sample points as the variation degree is smaller; an association unit configured to associate the selected sample points and three-dimensional measurement points obtained based on the coarse position and orientation; and a position/orientation determination unit configured to determine the position and orientation of the target object based on a result of the association unit.