3D projective geometry
These concepts generalize naturally to 3D
Homogeneous coordinates
Projective 3D points have four coords:  P = (X,Y,Z,W)
Duality
A plane N is also represented by a 4-vector
Points and planes are dual in 3D: N P=0
Projective transformations
Represented by 4x4 matrices T:  P’ = TP,    N’ = N T-1