Function SurfEvaluate

	Dim SurfObject: SurfObject = Rhino.GetObject("Select a surface",8)
	'prompt the user to select a surface for the function
	dim i
	dim UvalOne(1), UvalTwo
	dim SurfaceUone, SurfaceVone
	dim PointOne, PointTwo
	dim Pt1, Pt2, Pt3, Pt4
	dim NumVarU: NumVarU = 5
	dim NumVarV: NumVarV = 7
	dim FourPtCluster:  FourPtCluster=Array(Pt1,Pt2,Pt3,Pt4)
	redim Matrix (NumVarU, NumVarV)
	dim tempPt
	SurfaceUone = array (0,0)
	SurfaceVone = array (0,0)
	
	'test to be sure it is a surface, then find the domain in U and V
	If Rhino.IsSurface(SurfObject) Then
		SurfaceUone = Rhino.SurfaceDomain(SurfObject, 0)
		SurfaceVone = Rhino.SurfaceDomain(SurfObject, 1)
		'Rhino.Print "Domain in U direction: " & CStr(SurfaceUone(0)) & " to " & CStr(SurfaceUone(1))
		'Rhino.Print "Domain in V direction: " & CStr(SurfaceVOne(0)) & " to " & CStr(SurfaceVOne(1))
	End If

	'create a 2-D array called Matrix to hold all the points along the surface
	'the variables NumVarU and NumVarV determine the number of segments the 
	'surface will be divided into in each direction
	for i=0 to NumVarU
		for j=0 to NumVarV
		UvalOne(0)=((SurfaceUone(1)-SurfaceUone(0))/NumVarU)*(i)
		UvalOne(1)=((SurfaceVone(1)-SurfaceVone(0))/NumVarV)*(j)
		
		PointOne=Rhino.EvaluateSurface(SurfObject,UvalOne)
		tempPt = Rhino.addpoint(PointOne) 'creates points to mark the divisions
		
		Matrix(i,j) = PointOne 'creates a "master" array which will pass points to another function
		
		next
	next

	for i=0 to NumVarU-1
		for j=0 to NumVarV-1
		Pt1 = matrix(i,j)
		Pt2 = matrix(i+1,j)
		Pt3 = matrix(i+1,j+1)
		Pt4 = matrix(i,j+1)
		
		call XGrid(Pt1,Pt2,Pt3,Pt4)
		
		next

	next
		
end function

function XGrid(Pt1,Pt2,Pt3,Pt4)
	'this function uses the pipe comand to connect four points with a solid
	'perimeter and cross bracing

	dim linonetwo, lintwothre, linthrefour, linfourone, linonethre, lintwofour
	
	'draw lines connecting all the points
	linonetwo = Rhino.AddLine (Pt1, Pt2)
	lintwothre = Rhino.AddLine (Pt2, Pt3)
	linthrefour = Rhino.AddLine (Pt3, Pt4)
	linfourone = Rhino.AddLine (Pt4, Pt1)
	linonethre = Rhino.AddLine (Pt1, Pt3)
	lintwofour = Rhino.AddLine (Pt2, Pt4)
	
	'create pipes running along each of the lines
	Rhino.SelectObject (linonetwo)
	Rhino.Command "pipe "&".1 "&".1 "&" "
	Rhino.UnselectAllObjects
	
	Rhino.SelectObject (lintwothre)
	Rhino.Command "pipe "&".1 "&".1 "&" "
	Rhino.UnselectAllObjects
	
	Rhino.SelectObject (linthrefour)
	Rhino.Command "pipe "&".1 "&".1 "&" "
	Rhino.UnselectAllObjects
	
	Rhino.SelectObject (linfourone)
	Rhino.Command "pipe "&".1 "&".1 "&" "
	Rhino.UnselectAllObjects
	
	Rhino.SelectObject (linonethre)
	Rhino.Command "pipe "&".1 "&".1 "&" "
	Rhino.UnselectAllObjects
	
	Rhino.SelectObject (lintwofour)
	Rhino.Command "pipe "&".1 "&".1 "&" "
	Rhino.UnselectAllObjects

End function

call SurfEvaluate