Through the history of the interface technology development, one big and infinity challenge is unifying the physical world and the virtual world together. This challenge includes two aspects at least. One is to create a virtual projection that can be precisely equally perceived as its origins in the physical world. The other is operating the virtual projection by physically input on the projection directly.

Before the first GUI(graphic user interface) came out in 1981, we perceived this world with our eyes and operated it with our hands. Think about the process of an action. We start with an intention. And then our brains map the intention with the target objects and begin to understand the meanings and functions of them by the related memory and experience. Our hand will stretch out following our understanding, and meanwhile, our brain will receive the feedback and adjust the knowledge of the target object. At that stage, because of the simple tasks and their simple operation logic, our brain-to-hand process can be programmed by ourselves and can be adjusted through by the perceived feedback immediately.

A “brain-to-hand” model of human perceive, understand and operate process.Start with an intention, our brains map the intention with the target objects and begin to understand the meanings and functions of them by the related memory and experience. Our hand will stretch out following our understanding, and meanwhile, our brain will receive the feedback and adjust the knowledge of the target object. We can program the logic and adjust the operation by the perceived feedback immediately only when the tasks’ complexity is within our capability.

Because of the confliction of the limitation of human capability and the growth of complexity of our tasks, it becomes impossible for us to create the brain-to-hand process ourselves according to the instant feedback. Therefore, the division of labor in society evaluates and assigns some professions(we usually call them craftsman, inventors, designers, and engineers) with the responsibility to program the brain-to-hand processes in advance and create intermediate objects with interpretative logic for the others. By providing us with replacements of the actual objects we hope to operate, we can still implement this brain-to-hand process, but only to the intermediate objects to finish more complicated and challenging tasks. The button is one of the most typical intermediate objects ever designed. For example, before the button was invented, the first idea comes to our mind when we need light is perhaps to create fire. However, now we use light switch button with minimal thinking about what is going on between the button and the lightbulb. The operation can be understood and adjusted by instant feedback as we have brain memory and skin feeling.

From button to GUI, there are mainly two requirements for the design of the intermediate objects:

(1)to move the intermediate object from its original target object end to the users’ end;

(2)to reduce the understand and operation burden.

For the requirement one, what we do is to cover most of the distance, which represents the complexity of the tasks, from users to the target object. For example, 3d printer packed very complicated program under a single button on the software, and we can trigger a complicated process by a single click. For the requirement two, it is of vital importance to present the connections between the intermediate object and its origin in an understandable way. We have multiple approaches such as providing visual cues, implementing the universal standard, and immediate tactile feedback to let us operate with the muscle memory and intuition.

With the continuous effort, the intermediate objects now are so close to the users and sometimes even reach users’ end. Examples are like body gesture control of Kinect or the touchless interaction of Project Soli. Meanwhile, the understand and operation burden is low enough for users. The development of augmented reality can even attach the intermediate object( the computer-stimulated effect for AR example) directly to its origin and provide the visual and auditory perceptions equal to its origin in the physical world. However, we can still effortlessly distinguish the intermediate objects from its origin.