Real camera and virtual camera

A virtual camera for 3D graphics rendering is generally represented by two main sets of parameters: the extrinsic and intrinsic parameters. The extrinsic parameters define the location of the camera in the virtual world (the transformation from the world coordinate system to the camera coordinate system and vice versa). The intrinsic parameters define the projective properties of the camera, including its field of view (focal length), image center, and skew. Both the parameters can be represented with different data structures, with the most common being a matrix.

If you develop a 3D mobile game, you are generally free to configure the cameras the way you want; you can put the camera above a 3D character running on a terrain (extrinsic) or set up a large field of view to have a large view of the character and the terrain (intrinsic). However, when you do Augmented Reality, the choice is constrained by the properties of the real camera in your mobile phone. In...