We interact with objects in the real world for many reasons. You might eat a bowl of soup by moving a spoon between the bowl and your mouth. You might pick up a rock and throw it as far as possible. You might put on a pair of pants. These examples and many more fall under the topic of manipulation. In the real world, manipulation involves complex sensorimotor relationships which, through evolution and experience, enable us to manipulate objects under a wide variety of settings. The variation of objects includes differences in size, weight, friction, flexibility, temperature, fragility, and so on. Somehow our bodies can handle that. Getting robots to perform the manipulation in the ways that humans do has been a long and frustrating road, with only limited success .
Because of manipulation complexity in the real world, it is an ideal candidate for applying the remapping concepts from Section 10.1 to make manipulation as simple as possible in VR. The virtual world does not have to follow the complicated physics of manipulation. It is instead preferable to make operations such as selecting, grasping, manipulating, carrying, and placing an object as fast and easy as possible. Furthermore, extensive reaching or other forms of muscle strain should be avoided, unless the VR experience is designed to provide exercise.