Basic concepts

This document introduces some basic concepts related to VR application development, including virtual reality, VR all-in-one machine, degree of freedom, etc.

Virtual reality

Since the birth of personal computers in the 1970s, human beings have experienced many changes in human-computer interaction, from text commands to 2D graphical interaction, and then to mobile Internet. The continuous exploration of human beings has brought about the rapid development of digital technology, which makes digital computing more personal and miniaturized, and also makes the interaction between human beings and the digital world more "real", eventually giving birth to Virtual Reality (VR) technology. VR technology has dramatically changed the way we interact with the digital world. Through this technology, we can rely on visual, auditory, tactile and other sensory experiences to perceive the virtual world, and interact with the scenes, objects and characters in the virtual world, so as to obtain a strong sense of presence. In order to achieve this sense of presence, we need to let the brain see the virtual world as "real". The human brain processes what the sensory organs are currently capturing, creating a sense of presence. Therefore, in theory, we do not need to use VR to copy the real world 100% to deceive the brain to feel "existence", but only to provide the right sensory input to the brain and design a good VR experience, so that the brain thinks that what it sees in front of it is "real". PANCAKE VR technology solutions can help VR creators move towards this goal. On the basis of the concept of VR, three concepts of mixed reality, augmented reality and extended display are derived:

Concept	introduces
Mixed Reality	Mixed Reality (MR) refers to the combination of real and virtual worlds to create a virtual and real scene, in which physical entities and digital objects coexist and interact in real time. Ideally, MR devices create virtual objects that are indistinguishable from real objects.
Augmented Reality	Augmented Reality (AR) refers to the application of virtual information to the real world, which is difficult to experience in a certain time and space range of the real world (visual information, sound, taste, touch, etc.) After simulation and superposition, so that human beings can achieve sensory experience beyond reality. Virtual objects created by AR devices can be clearly seen as virtual.
Extended Reality	Extended Reality (VR) refers to a combination of real and virtual, human-computer interactive environment generated by computer technology and wearable devices. VR includes augmented reality, virtual reality, mixed reality and other forms, which is a general term for these concepts.

VR all-in-one machine

A complete VR solution needs VR equipment. VR all-in-one machine is a virtual reality head-mounted display device with independent processor, which can be used immediately. Its function is not as powerful as that of external VR device, but it has no connection constraints and has a higher degree of freedom. A PANCAKE VR all-in-one machine consists of a highly integrated head-mounted display (Head Mounted Display, HMD) and two Controllers (mainly referring to handles at present).

Degrees of freedom

Type	introduces
3DoF	The 3 Degree of Freedom. In 3DoF, the device can detect the rotation of the head in the direction of three coordinate axes (X, Y, Z), such as head tilt and back tilt, so as to sense the change of visual angle caused by head rotation.
6DoF	6 Degree of Freedom. In 6 DoF, in addition to sensing the user's head rotation on the X, Y, and Z axes, the device can also sense the parallel movement of the user's body on the three axes (up and down, left and right, and back and forth). Therefore, the VR headwear of 6 DoF allows users to make more diverse movements, such as walking, jumping and squatting.

Other

Concept	introduces
SUI	UI interface on the PANCAKE VR operating system.
Input	An event, such as pressing the trigger key, that occurs when a user interacts with the virtual world through the head-mounted display and joystick. When developing VR applications, input mapping needs to be set in the game engine.
Render	Refers to the process of creating a 3D model or designing a 3D image. Bring 3D models to life with precision, flexibility, detail, background, lighting, and other elements.
Field of view	Field of view (FOV). In VR equipment, the angle of view is the angle between the two sides of the display and the eye line. The size of the viewing angle of the head display directly determines the user's immersion.
XR Origin	XR Origin is the center of the tracking space in the virtual scene, which is used to track the position and posture of VR devices and users, and map them to the corresponding position and posture in the virtual world.