9.10 Design Guidelines
Throughout this chapter, we have presented many design guidelines for specific 3D system control techniques. In this section, we summarize some general guidelines. Because there still have not been many empirical evaluations of system control techniques for 3D UIs, however, most of the guidelines should be regarded as rules of thumb.
System control is often integrated with another 3D interaction task. Such a task structure forms a chain of actions. Because of this integration, system control techniques should be designed to avoid disturbing the flow of action of an interaction task. Lightweight mode switching, physical tools, and multimodal techniques can all be used to maintain the flow of action.
One of the major interruptions to a flow of action is a change of focus. This may occur when users have to cognitively and/or physically switch between the actual working area and a system control technique, or even when they must look away to switch devices.
Especially with “invisible” system control techniques like voice and gesture input, users will need to discover what is possible with the application. Make sure to aid this process by providing cues within the application or (alternatively) introduce a training phase.
Always provide clear feedback to the user so that she knows which interaction mode is currently active.
Placing your system control technique in the right position can make a big difference in its usability. Users often get distracted when searching for a way to change the mode of interaction or issue a command. If the controls are not visible at all, placed far away from the actual work area, or not oriented toward the user, the result will be wasted time. On the other hand, system controls attached to the user’s hand, body, or a device are always available.
There are several good techniques for structuring the functionality of an application, including hierarchical menu structures and context-sensitive system control. In cases where the number of functions is so large that these techniques are not effective, it can make sense to place some of the system control functionality on another device, such as a tablet, where resolution and selection accuracy are less of an issue.
Using multimodal input can provide more fluid and efficient system control but can also have its drawbacks.
Just because the applications are inherently 3D, 3D system control techniques are not necessarily the best solution. Often a 2D technique is more straightforward, especially if a tablet or phone can be used for controlling the menus. However, take care when designing interfaces that require a great deal of switching between modalities.