'------------------------------------------------------------------------------
' RhinoScript Code To Export Airfoil .Dat file for evaluation by DesignFoil
' XFOIL, VisualFoil or the Multisurface Aerodynamics VLM program  
' it uses the UIUC database format input. 
'tested on Rhino Version 3, SR 5b and all these analysis programs
' DesignFoil by John Dreese, XFOIL by Mark Drela and Harold Youngren
' VisualFoil, MutiSurface Aerodynamics by Patrick Hanley
' Written based on McNeel RhinoScript Example Files
' XFLR5, a re-write of XFOIL by Andre Deperrois which includes Miarex v1.0, 
' by Mathieu Scherrer. Very nice.
'------------------------------------------------------------------------------
Option Explicit
'------------------------------------------------------------------------------
' Subroutine:  ExportFoilDat
' Purpose:     Exports points on a NURB Based Foil Shape to a space-delimited file
' Discussion:  This subroutine will iterate through Points that lie on a curve starting from the
'              trailing edge, working along the upper surface then around the leading edge
'              then along the lower surface back to the trailing edge. This version groups using 
'              a cosine weighting scheme toward the leading and trailing edges
'              which yields much better resolution of fine details there
'              Join all splines together if split, adjust 'curve seam' to the trailing edge
'              and direction toward the top surface. The spline should wrap all the way-
'              as one spline. It Scales it to a Unit 1 Chord so it is non-dimensionalized
'              And Adjusts it to the Origin based on MinX, ChordY
'------------------------------------------------------------------------------
Sub ExportFoilDat()
Dim strObject, arrDomain, dblParam, arrPoint, Index, Steps,RawCos, DeltaCos,NextRawCos, arrEvalPts(),EvalPt
Dim dblLastParam, strFileName, strText,Scale,MinX,ChordY
Dim objFSO, objStream, i
strObject = Rhino.GetObject("Select the Foil Curve", 4)
'Steps = Rhino.GetInteger("number of steps", 200, 10, 2000)
'Dividing Cosine deltas by 4 is only good for 200 steps
'If you wish to not Cosine weight it, more steps can be used
' uncomment the above
Steps=200
strText=Rhino.StringBox("Description of Foil" )
arrDomain = Rhino.CurveDomain(strObject)
dblParam=0

For Index = 0 To Steps
        dblLastParam=dblParam
'     Original uniform spacing;
      	dblParam = arrDomain(0)+((arrDomain(1)-arrDomain(0))/Steps)*Index
        'calc Cos Spacing;
''        RawCos=abs(cos(((Index)/Steps)*6.28318531))
''        NextRawCos=abs(cos(((Index+1)/Steps)*6.28318531))
''        DeltaCos=abs(RawCos-NextRawCos)/4
''        If Index=0 then
''        	dblParam = (DeltaCos*(arrDomain(1)-arrDomain(0)))+arrDomain(0)
''          Else
''        	dblParam = (DeltaCos*(arrDomain(1)-arrDomain(0)))+dblLastParam
''        End If
	EvalPt = Rhino.EvaluateCurve(strObject, dblParam)
        If Index=0 then
           MinX=EvalPt(0)
           ChordY=EvalPt(2)

        End IF
        If EvalPt(0)<MinX then MinX=EvalPt(0)
        redim preserve arrEvalPts(Index)
        arrEvalPts(Index)=EvalPt
	Rhino.AddPoint(EvalPt)
Next
       Rhino.Print "MinX=" & FormatNumber(MinX,4)
	strFileName = Rhino.SaveFileName ("Data File Name", "Data Files (*.Dat)|*.Dat||")
	If VarType(strFileName) = vbString Then
 		Set objFSO = CreateObject("Scripting.FileSystemObject")
		On Error Resume Next
		Set objStream = objFSO.CreateTextFile(strFileName, True)
		If Err Then
			MsgBox Err.Description
			Set objStream = Nothing
			Set objFSO = Nothing
		Else
		objStream.WriteLine(strText)
                    Scale=1/(EvalPt(0)-MinX)
			For i = 0 To Steps
			       EvalPt=arrEvalPts(i)
                                EvalPt(0)=(EvalPt(0)*Scale)-(MinX*Scale)
                                EvalPt(2)=(EvalPt(2)-ChordY)*Scale
				strText = FormatNumber(EvalPt(0),6) & " " & FormatNumber(EvalPt(2),6)
				objStream.WriteLine(strText)
			Next
			objStream.Close
			Set objStream = Nothing
			Set objFSO = Nothing
		End If
	End If
End Sub