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 = 7
	dim NumVarV: NumVarV = 9
	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 DrawPyramid(Pt1,Pt2,Pt3,Pt4)
		
		next

	next
		
end function

Function DrawPyramid(Pt1,Pt2,Pt3,Pt4)
	'this function draws a sufrace from 4 points, finds the center of that surface,
	'then draws a line along the normal at this point in order to build surfaces
	'up from base surface

	dim tempsrf, arrDomainU, arrDomainV, arrDirection
	dim arrParam(1),arrNormal,LineNormSmall, LineNormBig, arrPtDomain, arrPtParam
	dim Pt5, Pt6
	dim sideone, sidetwo, sidethree, sidefour
	
	'draw a surface using the four points passed from the Matrix
	tempsrf = rhino.addsrfpt (Array(pt1,pt2,pt3,pt4))

	'using the domain values for U an V, divide their difference by two
	'to get array parameters, then evaluate the surface to find the midpoint
	arrDomainU = Rhino.SurfaceDomain(tempsrf, 0)
	arrDomainV = Rhino.SurfaceDomain(tempsrf, 1)
	arrParam(0) =(arrDomainU(1)-arrDomainU(0))/2
	arrParam(1) =(arrDomainV(1)-arrDomainV(0))/2 
	Pt5 = Rhino.EvaluateSurface(tempsrf, arrParam)
	Rhino.AddPoint Pt5 'add a point at the center of tempsrf

	'find the normal of the surface at Pt5 and draw a line, then extend the line
	arrNormal = Rhino.SurfaceNormal (tempSrf, arrParam)
	LineNormSmall = Rhino.AddLine (arrNormal(0), arrNormal(1))
	'LineNormBig = Rhino.ExtendCurveLength (LineNormSmall, 0,1,7*rnd) 'creates random height
	LineNormBig = Rhino.ExtendCurveLength (LineNormSmall, 0,1,10)
	
	'reverse the direction of the surface in order to extrude in the opposite direction
	Rhino.SelectObject (tempsrf)
	Rhino.Command "Flip "
	arrNormal = Rhino.SurfaceNormal (tempSrf, arrParam)
	LineNormSmall = Rhino.AddLine (arrNormal(0), arrNormal(1))
	Rhino.ExtrudeSurface tempSrf,LineNormSmall 'make a base from the surface
	
	'make a new point using the domain of the extended line
	arrPtDomain = Rhino.CurveDomain(LineNormBig)
	arrPtParam = arrPtDomain(1)
	Pt6 = Rhino.EvaluateCurve(LineNormBig, arrPtParam)
	Rhino.AddPoint Pt6
	
	'draw a pyramid w/ four sides using Points 1,2,3,4,and 6
	sideone = rhino.addsrfpt (Array(pt1,pt2,pt6))
	sidetwo = rhino.addsrfpt (Array(pt2,pt3,pt6))
	sidethree = rhino.addsrfpt (Array(pt3,pt4,pt6))
	sidefour = rhino.addsrfpt (Array(pt4,pt1,pt6))
	
End Function

call SurfEvaluate