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Interaction techniques for a virtual workspace

1 Motivation

Much work in VR has focused on the 'sense of immersion' as the gold standard of quality. Most visits to such realities leave them unchanged. We aim to provide an interaction environment with virtual tools controlled through material devices, in which to perform precise, accurate 3D work (resolution in millimetres) for work sessions of serious length (3 to 4 hours at a time). This is necessary for the medical applications we are developing[1], and applicable to such diverse fields as CAD, welding planning and training, and 3D sketching. The medical applications allow one, for example, to edit multiple computer estimates of the moving heart boundary, for strain analysis that reveals ischæmic muscle, or to define central curves for arteries, nerves, etc., detectable in volume data and in 3D space. We use the Virtual Workbench [15], a robust environment for general 3D manipulation tasks (see Section 4). Most 3D interfaces are based either

• on the head mounted 'immersive' paradigm, (e.g.,[3][22]) where low resolution, long drawing delays for complex objects (and consequent simulator sickness), and calibration problems, combine to make accurate work extremely hard;
• on a directly viewed stereo display [2][7], in which the hand and its position sensor cannot go behind any part of the display without obscuring the screen and destroying stereo. When such systems use negative parallax to bring the display 'in reach' in front of the screen, they create conflict between the stereo and lens-accommodation depth cues.

Calibration of the Virtual Workbench is straightforward, and cues from the single-eye focus and two-eye stereo fusion are in better accord. Here, we concentrate on interface design, leaving calibration, precision, predictive filtering etc. to papers already presented [15], [11].

To date, the VR community has paid limited attention to how the user interacts with application aspects beyond the simulated 3D reality, such as access to system functions and tools, status, help and other information, all vital for professional uses of VR in for instance medicine, architecture and collaborative design. In [23] we refer to the necessary means as VR management tools.

There are two classes of these: Manipulators, an integral part to the VR, include such 'virtual tools' as scalpel, calipers, hammer, pen, and so on. Selectors such as menus and sliders show a range of options and/or provide status information. Selectors tend to be used in combination with manipulators; for example, selecting from a menu with a button-pusher manipulator.

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