DPlane3d is formed from an origin and a Normal:

	new DPlane3d(ref DPoint3d Origin, ref DVector3d Normal)
	new DPlane3d(double ax, double ay, double nx, double
ny)
	new DPlane3d(double ax, double ay, double az, double
nx, double ny, double nz)

Normal

	planeD3d.Normal
	planeD3d.NegateNormalInPlace()

STATIC method Intersect

	DPlane3d.Intersect(ref DPlane3d PlaneA, ref DPlane3d
PlaneB, out DRay3d Ray)
	DPlane3d.Intersect(ref DPlane3d Plane, ref Dray3d
Ray, out double RayFraction, out DPoint3d IntersectionPoint)
	DPlane3d.Intersect(ref DPlane3d Plane, ref DSegment3d
Segment, out double LineFraction, out DPoint3d IntersectionPoint)

Closest Point

	ClosestPoint(ref DPoint3d SpacePoint, out DPoint3d
ClosePoint)