Viewing cone
（重定向自Viewing Direction）
![Figure 1: Illustration of the variation of the direction of observation (i.e. viewing direction) across the area of the display. All locations on the surface area of the screen are seen from a different direction.](/Images/godic/202502/19/Viewing-directions-34558.gif")
![Figure 2: Illustration of an example of a viewing cone centered about the surface-normal of the display. The viewing cone may be tilted and rotated and may be of a less regular shape.](/Images/godic/202502/19/Viewing-Cone-16Mar084558.png")
![Figure 3: Illustration of the specification of the viewing direction by two polar angles: the angle of inclination (measured from the surface normal of the display) and the azimuth angle, measured in the plane of the display](/Images/godic/202502/19/Spherical-Coordinate-System-14559.png")
![Figure 4: Illustration of the specification of the range of viewing directions (aka viewing cone) in a polar coordinate system. The pseudo-colors represent the value of a physical quantity (e.g. luminance) for each viewing direction.](/Images/godic/202502/19/Viewing-Cone-mB14559.png")
When a visual display with non-vanishing size is seen by an observer, every point of the display area is seen from a different direction as illustrated in fig. 1. No two spots on the display are seen from the same direction. The larger the display is and the closer the observer is to the display the more the viewing direction varies over the surface area of the display.