Shape Discrepancy: Spherical vs Planar Surface of Projection
In the real world, objects from the environment surrounding us are mapped on our retina, inside the eye, to produce human vision. Yet the shape of the retina is sphere, which is a 3d element. Whereas objects in the virtual worlds are mapped on 2d planes of projection. This discrepancy between the the 3-dimentional sphere and the 2-dimensional plane is one the two core causes for the arise of perspective distortions.
Angle Discrepancy: Virtual Field of View vs Physical Field of View
The FOV and position of the viewer watching an animation on a screen never match exactly the FOV and position parameters at which the camera has captured the virtual scene rendered on the screen aforementioned. This very fact is the other core cause for the arise of distortions.
