12 Elements of a Three-dimensional Graphical User Interface Geoff Leach, Ghassan AI-Qaimari, Mark Grieve, Noel Jinks, Cameron McKay Department of Computer Science, RMIT, Melbourne, Vic., 3000, Australia {gllghassan}@cs.rmit.edu.au ABSTRACT The graphical user interface (GUI) is now firmly established as the preferred user interface for end users in most situations. Just as decreasing hardware prices and increasing hardware capabilities made two-and-a-hall dimensional (2!D) GUIs affordable in the early eighties and widespread in the ninetees, we believe declining hardware prices and increasing hardware capabilities will make three-dimensional (3D) GUIs possible and affordable in the near future. Three-dimensional GUIs raise many issues of design, metaphor and usability. In this paper we discuss elements of a prototype 3D GUI we are developing. KEYWORDS 3D graphical user interface, 3D window manager, 3D cursor, prototyping, usability. 1. Introduction The GUI was developed at Xerox PARC in the late seventies for the Star system (Shneiderman, 1992, Smith et a!., 1982). It was first successfully commer- cialised by Apple with the Macintosh computer in the early eighties and has since become an integral part of every modern operating system for personal computers and graphics workstations. One reason for this growth is productivity: a number of studies have shown GUIs, with their direct manipulation style of interaction, enhance productivity (Rauterberg, 1992, Margono and Shneiderman, 1987). Another reason is subjective preference: people express a preference for GUI interfaces. Coupled with the rise of the GUI has been a general elevation of the importance of the user in- terface, which is now recognised as a key, and sometimes central, component of an interactive product or environ- ment. Today's GUI depended on declining hardware prices to make it affordable at the low-end of the computer market - personal computers. The same trend, a dou- bling of performance approximately every 18 months to two years (widely known as Moore's Law), now means personal computers are capable of pcrform- ing interactive 3D graphics. In tandem with improv- ing hardware performance, graphics libraries such as OpenGL (Neider et a!., 1993) which were previously • A copy of the paper with colour figures is available at http://www.cs.rmit.edu.aurgllresearchlHCc/interact97.html available only on workstations have now become avail- able for personal computers. We believe that 3D GUIs - graphical user interfaces which utilise 3D graphics - offer significant potential for improvement over today's 2!D GUIs, and further- more, that it is now, or very shortly will be, possible to run such interfaces on personal computers. In this paper, we discuss elements of a prototype 3D GUI we are de- veloping and discuss some early feedback from usability tests. 2. Background The researchers and developers at Xerox PARC who produced the Star system were determined to produce a system far easier and more intuitive to use than the command-line interfaces which predominated at the time (Smith et a!., 1982). A key part of achieving this was providing a metaphor to integrate the visual elements of a graphical user interface into a recognisable and com- prehensible framework. In the desktop metaphor used for the Star, and for most commercial GUIs since, the interface is conceptualised and presented as a graphical version of a typical office. Its key elements are: • A desktop or space on which icons or small pic- tographs which correspond to commonly found equipment in offices (bins, printers, documents and folders) are placed. Human-Computer Interaction: INTERACT'97 S. Howard, J. Hammond & G. Lindgaard (editors) Published by Chapman & Hall ©IFIP 1997