Rays with endpoints and vectors.
Although a ray is isomorphic to a
SurfaceVertex3D, it does not have the
The parametric function of a ray. The parameter is measured as a
proportion of the length of the vector.
projectRay 0 is the
endpoint of the ray.
projectRay 1 is the endpoint offset
by the ray's vector.
The inverse operation to
projectRay. This could also be
understood as the height of the point above the plane defined
by the ray.
The angle between vector of the ray and the vector from the endpoint of the ray to the specified point.