Viewing frustum

[2] The view frustum is typically obtained by taking a geometrical frustum—that is a truncation with parallel planes—of the pyramid of vision, which is the adaptation of (idealized) cone of vision that a camera or eye would have to the rectangular viewports typically used in computer graphics.

[3][4] Some authors use pyramid of vision as a synonym for view frustum itself, i.e. consider it truncated.

[5] The exact shape of this region varies depending on what kind of camera lens is being simulated, but typically it is a frustum of a rectangular pyramid (hence the name).

The geometry is defined by a field of view angle (in the 'y' direction), as well as an aspect ratio.

Together this information can be used to calculate a projection matrix for rendering transformation in a graphics pipeline.