Z axis direction of a Cplane?

Hi all,
i need to determine in wich direction is oriented my cplanes Z axis

For example, i set a cplane on planar curves with Rhino.curvePlane.
on pictures we have 2 similar curves, but one put the Cplane Zaxis upside the other.

in script, arrPlane (3) return the Z axis, but i got a vector value, with 3 index, sometimes positive or negatives value depending of curves placement.

How can i determine the direction of my axis with these values ?

or may be another solution ?


Call Main()
Sub Main()
	Dim strCrv, arrPlane
	strCrv = rhino.getObject("Curve", 4)
	arrPlane = Rhino.CurvePlane(strCrv)
	Rhino.ViewCplane, arrPlane

End Sub

Hi @Cyver,

If you use the Dir command, you will notice that the directions of the two curves do not match. A planar curve whose direction is counter-clockwise will have it’s plane normal facing upwards. Likewise, a planar curve whose direction is clockwise will have it’s plane normal facing downwards.

– Dale

Hi Dale,
thanks for reply.

Yes, i already tought to use Rhino.ClosedCurveOrientation to check curves direction, but i also use open planar curves , and i can’t use this method on open curve, that’s why i tried to determine cplane Z axis direction made by Rhino.curvePlane.