Perspective projection
= Perspective projection
Projection from a fixed centre onto an image plane. With centre at the origin and plane $z=f$, a <point> $(x,y,z)$ with $z\ne0$ maps to $(fx/z,fy/z,f)$. The image-plane convention may put the plane in front of the centre, giving a virtual upright image, or behind it, giving an inverted physical image.