Developer: RhinoScript
Summary: Demonstrates how to create square pipes using RhinoScript.

 Option Explicit
 
 Sub SquarePipe()
 
   ' Pick the input, or path, curve
   Dim strCrv
   strCrv = Rhino.GetObject( "Select curve", 4 )
   If IsNull( strCrv ) Then Exit Sub
 
   ' Specify the lengths of the sides of the square    
   Dim dblLength
   dblLength = Rhino.GetReal( "Length of sides", 1.0, 0.0 )
   If Not IsNumeric(dblLength) Or dblLength <= 0 Then Exit Sub
 
   ' Determine the curve's starting point    
   Dim arrStart
   arrStart = Rhino.CurveStartPoint( strCrv )
 
   ' Determine the parameter at the starting point  
   Dim dblParam
   dblParam = Rhino.CurveClosestPoint( strCrv, arrStart )
 
   ' Detemine the curve's curvature at the starting point. This 
   ' will return two vectors that we can use to cook up the
   ' coordinates of the square
   Dim arrCurvature
   arrCurvature = Rhino.CurveCurvature( strCrv, dblParam )
 
   ' Cook up x, y, and z vectors  
   Dim arrX, arrY, arrZ
   arrZ = VectorUnitize( arrCurvature(1) )
   arrX = VectorUnitize( arrCurvature(4) )
   arrY = VectorUnitize( VectorCrossProduct(arrZ, arrX) )
 
   ' Scale the vectors based on the user input
   arrX = VectorScale( arrX, dblLength )
   arrY = VectorScale( arrY, dblLength )
 
   ' Cook up some temporary points
   Dim x0, x1, y0, y1
   x0 = PointAddVector( arrStart, arrX )
   x1 = PointAddVector( arrStart, VectorNegate(arrX) )
   y0 = PointAddVector( arrStart, arrY )
   y1 = PointAddVector( arrStart, VectorNegate(arrY) )
 
   ' Define the points of the square  
   Dim arrPoints(4)
   arrPoints(0) = PointAddVector( x0, VectorNegate(arrY) )
   arrPoints(1) = PointAddVector( y1, VectorNegate(arrX) )
   arrPoints(2) = PointAddVector( x1, arrY )
   arrPoints(3) = PointAddVector( y0, arrX )
   arrPoints(4) = arrPoints(0)
 
   ' Create the square
   Dim strSqr
   strSqr = Rhino.AddPolyline( arrPoints )
 
   ' Extrude the polyline along the input curve
   Rhino.ExtrudeCurve strSqr, strCrv
 
   ' Delete polyline
   Rhino.DeleteObject strSqr   
 
 End Sub
 
 Public Function VectorUnitize(v)
   VectorUnitize = Null
   If Not IsArray(v) Or (UBound(v) <> 2) Then Exit Function
   Dim dist, x, y, z, x2, y2, z2
   x = v(0) : y = v(1) : z = v(2)
   x2 = x * x : y2 = y * y : z2 = z * z
   dist = x2 + y2 + z2
   If (dist < 0.0) Then Exit Function
   dist = Sqr(dist)
   x = x / dist
   y = y / dist
   z = z / dist
   VectorUnitize = Array(x, y, z)
 End Function
 
 Public Function VectorNegate(v)
   VectorNegate = Null
   If Not IsArray(v) Or (UBound(v) <> 2) Then Exit Function
   VectorNegate = Array(-v(0), -v(1), -v(2))
 End Function
 
 Public Function VectorCrossProduct(v1, v2)
   VectorCrossProduct = Null
   If Not IsArray(v1) Or (UBound(v1) <> 2) Then Exit Function
   If Not IsArray(v2) Or (UBound(v2) <> 2) Then Exit Function
   Dim x, y, z
   x = v1(1) * v2(2) - v1(2) * v2(1)
   y = v1(2) * v2(0) - v1(0) * v2(2)
   z = v1(0) * v2(1) - v1(1) * v2(0)
   VectorCrossProduct = Array(x, y, z)
 End Function
 
 Public Function VectorScale(v, d)
   VectorScale = Null
   If Not IsArray(v) Or (UBound(v) <> 2) Then Exit Function
   If Not IsNumeric(d) Then Exit Function
   VectorScale = Array(v(0) * d, v(1) * d, v(2) * d)
 End Function
 
 Public Function PointAddVector(p, v)
   PointAddVector = Null
   If Not IsArray(p) Or (UBound(p) <> 2) Then Exit Function
   If Not IsArray(v) Or (UBound(v) <> 2) Then Exit Function
   PointAddVector = Array(p(0) + v(0), p(1) + v(1), p(2) + v(2))
 End Function