[Table of Content] [Appendices] [Abstract] [Summary] [Chapter 1] [Chapter 2] [Chapter 3] [Chapter 4] [Chapter 5] [Chapter 6]

Human Performance in Six Degree of Freedom Input Control

Shumin Zhai, Ph.D.

5.5 Applications

In the experiment, a silk cursor in a box shape was used to demonstrate the effect that semi-transparency surfaces introduce an extra cue in revealing users actions in relation to targets in 3D space. A 3D cursor can have many other shapes. In fact, a silk cursor with a tetrahedral shape has been used in Experiment 3 (Figure 3.11). As can be seen in Figure 3.9, a silk cursor with such a shape reveals the relationship between the target and the cursor both in translation and in orientation.

Another more complex shape of 3D cursor is the hand metaphor often used in VR applications. Such a cursor can be drawn either in solid colour or in wireframe. However, given the various manipulative functions of the hand representation, many of which involve occlusion of underlying objects, rendering the hand in semi-transparency for such applications, as illustrated in Figure 5.14, is expected to be beneficial.


Figure 5.14 A proposed "silk hand" for VR applications



Figure 5.15 The "silk phantom robot" for telerobot control.(Courtesy of Anu Rastogi)

An even more complex form of 3D cursor is a graphical robot (Figure 5.15). In order to off-load human operators from the task of continually having to control a telerobot in real time, some researchers have developed the technique of planning the slave robot movements by means of a graphical/virtual robot model (Bejczy, Kim, and Venema, 1990; Funda, Lindsay, and Paul, 1992; Zhai and Milgram, 1991, Milgram et al, 1995) . Such a "phantom robot" (Bejczy, et al. 1990) is usually drawn in a solid colour or wireframe. A "silk phantom robot" (Figure 5.15) drawn in semi-transparency could allow the operator to see objects behind the robot and better to visualise operations, particularly when the robot is in close proximity to obstacles and targets.

In conclusion, this chapter has investigated semi-transparency as a potentially powerful depth cue, to be used alongside such established 3D graphic techniques as perspective projection, stereoscopic displays, motion parallax and viewpoint tracking. Such a depth cue is particularly useful for displaying users' input actions in 3D space for manipulation of target objects.