Implements the plane optimal shadow camera algorithm.
Given a plane of interest, it is possible to set up the shadow camera
matrix such that the mapping between screen and shadow map is the identity
(when restricted to pixels that view the plane of interest). Therefore,
if the shadow map resolution matches the screen space resolution (of the
seen planar receiver), we can get pixel perfect shadowing on the plane.
Off the plane, the shadowing is not guaranteed to be perfect and will
likely exhibit the usual sampling artifacts associated with shadow mapping.
 Note
 Important: this routine requires doubleprecision calculations. When you are running under Direct3D, you must ensure that you set the floating point mode to 'Consistent' rather than 'Fastest' to ensure this precision. This does allegedly come with some performance cost but when measuring it appears to be negligible in modern systems for normal usage.

Second important note: this projection also only works for lights with a finite position. Therefore you cannot use it for directional lights at this time.