Abstract: A visual display apparatus suitable for use with a viewing apparatus capable of providing stereoscopic view of an image from 360-degree directions around it, or a display apparatus capable of displaying an observation image that changes depending on what angle it is viewed at or who views it, is described. The visual display apparatus comprises a main optical system that is concentric and rotationally symmetric about a center axis and a plurality of subordinate optical systems of identical construction, which are juxtaposed on a circumference concentric about the center axis. A combined optical system comprising the main optical system and each subordinate optical system has an exit pupil positioned on a side of the main optical system that faces away from each subordinate optical system and on a side of the center axis that faces away from each subordinate optical system on an optical path.

Abstract: Exemplary methods are provided. In one exemplary method, a lower-dimension signature is generated for each of a plurality of data sets of a given dimension. Registration is performed on the lower-dimension signatures. In another exemplary method, a two-dimensional signature is generated for each of a plurality of three-dimensional volumes. Registration is performed on the two-dimensional signatures.