The capability to display three-dimensional (3D) information in a realistic way has long been sought after1, and is particularly useful in scientific visualisation, where the ability to view spatial data can greatly clarify understanding in such fields as medical diagnostics, molecular modelling and computer-aided design. The essence of 3D display systems2 is their ability to provide the viewer's visual system with the information required for a greater number of the depth cues', by which our brains perceive relative spatial relationships within images, than is possible with conventional terminals. Probably the most important of these cues is binocular parallax, where depth is gauged by the brain's interpretation of slight differences in the image received by each eye. This is the impetus behind a wide range of display technologies where each of a viewers eyes is artificially provided with a slightly different view of the same image, often (but not always) via special glasses or headgear. Temporal paralha, where a depth effect is gained through a changing orientation of a 3D object, is also very effective, and has been used extensively to aid the interpretation of 3D images on conventional 2D computer termins.