We describe a system for manoeuvring a three-dimensional object on screen which combines analogue elements with icons. We call it ICAS (Icon cum Analogue System). An experiment examines the benefits of each component of ICAS. Psychological considerations led us to use multiple measures in the experiment, and to use both regular and irregular objects. Results show that two of our controls are useful at least in certain circumstances, whereas the third is never beneficial and sometimes impairs performance. The results are not compatible with design principles that are widely accepted, or with extreme commitment to the ideal of virtual reality. We argue that this illustrates the need for interface design to exploit the duality of its medium - as a screen in the real world and a depiction of things in a virtual world - as older graphic media have done. That involves accepting that virtual realities can and should be magical, and that in interface design, understanding the mind is as fundamental as underst.wding the world.
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