1. An apparatus, comprising: a storage medium configured to store a plurality of reference images of an object comprising a concave region; a silhouette processing module configured to: obtain the plurality of reference images from the storage medium, and obtain a silhouette for each of the plurality of reference images; and a virtual-image synthesis module configured to: generate a visual hull for the object having the concave region based on the silhouette for each of the plurality of reference images, and generate a virtual inside-out image of the concave region based on the visual hull.