Rhino Surface help please

Rhino Rhino for Windows
9

The idea behind my geometry was to create a surface the behaved more like a true Moebius. By that I mean that the surface can be evaluated through the U direction to a position on both sides. See the script.

I chose 4Pi to resemble a circle. With a circle, advancing 2Pi will return you to the start point. With a Mobius, you are at the start point, but on the underside of the surface. 4Pi returns you to the true start point.

Option Explicit

Sub SurfNormAtParam
	Dim srf
	Dim domU, domV
	Dim domInput(1)
	Dim tanVec
	Dim arrdata



	With Rhino
		srf = .GetObject("Pick a surface", 8)
    
		If (VarType(srf) <> vbString) Then Exit Sub
    
		
		domU = .SurfaceDomain(srf, 0)
		domInput(0) = .GetReal("U Param, input Real Number between " & CStr(DomU(0)) & " and " & CStr(DomU(1)), DomU(0), DomU(0), DomU(1))
		
		
		domV = .SurfaceDomain(srf, 1)
		domInput(1) = .GetReal("V Param, input Real Number between " & CStr(DomV(0)) & " and " & CStr(DomV(1)), DomV(0), DomV(0), DomV(1))
		
		arrdata = .SurfaceCurvature(srf, domInput)
		     
		tanVec = .AddLine(arrdata(0), .PointAdd(arrdata(0), arrdata(1)))
		
      
	End With
End Sub
SurfNormAtParam