With respect to a space including an object 40 of a display target, images of the space viewed from reference points 42a to 42c of view are created as reference images 46a, 46b, and 46c in advance and they are synthesized according to a position of an actual point of view to render a display image. In the certain reference image 46b, data other than a part 48 represented only in it is deleted. At the time of rendering of the deleted part, the other reference images 46a and 46c are used.