A DRay can be created from an origin and a Target or alternatively an origin and a direction vector:

	DRay3d(ref DPoint3d Origin, ref DPoint3d Target)
	DRay3d(ref DPoint3d Origin, ref DVector3d Direction)

Use the Direction property to extract a vector from a Dray3d

	Direction()

Normalised Direction

	NormalizedDirection()

IntersectXY

	DRay3d.IntersectXY(ref DRay3d rayA, ref DRay3d 
rayB, out double fractionA, ref DPoint3d pointA, out double fractionB,
ref DPoint3d pointB)

Point at Fraction

	DRay3d.IntersectXY(ref DRay3d rayA, ref DRay3d 
rayB, out double fractionA, ref DPoint3d pointA, out double fractionB,
ref DPoint3d pointB)

Point at Fraction

	PointAtFraction(ref double fraction)
	PointAtFraction(ref double fraction, DVector3d Derivative1)
	PointAtFraction(ref double fraction, DVector3d Derivative1,
DVector3d Derivative2)