SectionArea.rvb

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' SectionArea.rvb -- July 2007
' If this code works, it was written by Dale Fugier.
' If not, I don't know who wrote it.
' Works with Rhino 4.0.
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Option Explicit

Sub SectionArea
  
  ' Prompt the user for the number of samples
  samples = 8
  samples = Rhino.GetInteger("Number of samples", samples, 2)
  If IsNull(samples) Then Exit Sub

  ' Prompt the user for the 'from' point
  pt0 = Rhino.GetPoint("Point to move from")
  If IsNull(pt0) Then Exit Sub

  ' Prompt the user for the 'to' point
  pt1 = Rhino.GetPoint("Point to move to", pt0)
  If IsNull(pt1) Then Exit Sub

  ' Prompt the user for the object to cut
  obj = Rhino.GetObject("Select closed volume to cut", 8)
  If IsNull(obj) Then Exit Sub

  ' Redim arrays
  Dim graph_points()
  ReDim graph_points( samples )
  
  ' Try to speed things up a bit
  Rhino.EnableRedraw False

  ' Add layers
  Rhino.AddLayer "sections", RGB(240, 20, 20)
  Rhino.AddLayer "cumulative area", RGB(20, 200, 20)

  ' Set the sections layer current  
  Rhino.CurrentLayer("sections")
  
  ' Create a vector from the two input points
  v = Rhino.VectorCreate(pt1, pt0)
  ' Get the length of the vector
  length = Rhino.VectorLength(v)
  ' Unitize the vector
  v = Rhino.VectorUnitize(v)
  ' Calculate the size of each interval
  interval = length / samples
  
  ' Repeat sample + 1 times
  For i = 0 To samples
    
    ' Plane origin
    origin = pt0
    ' Create plane from origin and vector
    plane = Rhino.PlaneFromNormal(origin, v)
    
    ' If i > 0, then move the plane along the defined axis
    If( i > 0 ) Then
      scale_v = Rhino.VectorScale(v, i*interval)
      origin = Rhino.PointAdd(pt0, scale_v)
      plane = Rhino.MovePlane(plane, origin)
    End If
    
    ' Add a point at the plane's origin
    Rhino.AddPoint origin
    
    ' Create section curves through the object
    sections = Rhino.AddSrfSectionCrvs(obj, plane)

    ' If there was more then one section curve
    ' try to union the curves together  
    If (UBound(sections) > 0) Then
      sections = Rhino.CurveBooleanUnion(sections)
    End If
    
    ' Calculate the area of the section curves
    area = Rhino.CurveArea(sections)
    
    ' Build a graphing point based on the plane's 
    ' origin, and the cumulative curve area
    graph_points(i) = Array(origin(0), area(0), 0)
   
  Next    

  ' Draw our graph
  Rhino.CurrentLayer("cumulative area")
  Rhino.AddInterpCurve graph_points
  Rhino.AddPoints graph_points

  ' Turn screen redrawing back on
  Rhino.EnableRedraw True

End Sub