1. A method for performing rendering using image data of three or more dimensions including a plurality of voxels of three or more dimensions, the method comprising: preparing an exfoliated picture generated by projecting voxels using cylindrical projection method with a center line; preparing position data of a cross-section and a cross-section image representing the cross-section of the image data; creating a hypothetical cylinder including position data using the center line; calculating relation information associating the hypothetical cylinder and the cross-section using position data of the hypothetical cylinder and position data of the cross-section; and synthesizing the relation information with at least one of the exfoliated picture and the cross-section image to generate a synthesized image.