In recent years, the technique is being applied also to fields such as information retrieval conventionally not related to virtual three-dimensional display (for example, Japanese Unexamined Patent Application Nos. 11-175534 and 2000-029885, and ???Visualization of Image Feature Space using VR Space???, by Hiroike, et al., IEICE Technical Report PRMU98-86 (1998-09), pp. 17 to 24). [0003] Movement