In the development of interaction mechanisms for VR, the main considerations are:
- Effectiveness for the task in terms of achieving the required speed, accuracy, and motion range, if applicable.
- Difficulty of learning the new motor programs; ideally, the user should not be expected to spend many months mastering a new mechanism.
- Ease of use in terms of cognitive load; in other words, the interaction mechanism should require little or no focused attention after some practice.
- Overall comfort during use over extended periods; the user should not develop muscle fatigue, unless the task is to get some physical exercise.
To design and evaluate new interaction mechanisms, it is helpful to start by understanding the physiology and psychology of acquiring the motor skills and programs. Chapters 5 and 6 covered these for visual perception, which is the process of converting sensory input into a perceptual experience. We now consider the corresponding parts for generating output in the form of body motions in the physical world. In this case, the brain sends motor signals to the muscles, causing them to move, while at the same time incorporating sensory feedback by utilizing the perceptual processes.
(a) Part of the cerebral cortex is devoted to motion. (b) Many other parts interact with the cortex to produce and execute motions, including the thalamus, spinal cord, basal ganglion, brain stem, and cerebellum. (Figures from www.thebrain.mcgill.ca.)
Steven M LaValle