What is Normal?
Normal is a term used in 3D visualization to describe the way an object is oriented in relation to other objects. In other words, it describes the angle at which an object is viewed.
Normal can also be used to describe the way an object is lit. In 3D rendering, light is often simulated by using a technique called ray tracing. Ray tracing calculates the path of light rays as they reflect off of surfaces. The angle at which a ray of light hits a surface is called the incident angle. The angle at which the ray reflects off of the surface is called the reflected angle. The angle between the incident angle and the reflected angle is called the normal angle.