1. A method of measuring a three-dimensional (3D) target object using two-dimensional (2D) patterns, comprising: selecting an initial two-dimensional pattern; laying the initial pattern on a 3D target object for viewing from a viewpoint to obtain a 2D transformed pattern; computing first depth information regarding the target object based on the transformed pattern; identifying a region of the target object that is hidden from the viewpoint or has a complexity above a predetermined threshold, based on the transformed pattern and first depth information; and computing second depth information different from the first depth information regarding the region of the target object.