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Extract Isocurve Intersection Points

Demonstrates how to get the intersection points of a surface's isocurves using RhinoScript.

VBScript

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' ExtractUVIntersectPts.rvb -- November 2008
' 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

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'Extracts surface wireframe curves
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Function RhExtractWireframe(sSurface)

  Dim aResults
  RhExtractWireframe = Null

  Call Rhino.SelectObject(sSurface)

  Call Rhino.Command("_-ExtractWireframe", 0)
  aResults = Rhino.LastCreatedObjects
  If IsArray(aResults) Then
    RhExtractWireframe = aResults
    Rhino.UnselectObjects(aResults)
  End If

  Call Rhino.UnselectObject(sSurface)

End Function

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'Intersects curves
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Function RhIntersect(aCurves)  

  Dim aResults, aPoints(), i
  RhIntersect = Null

  Call Rhino.SelectObjects(aCurves)  

  Call Rhino.Command("_-Intersect", 0)
  aResults = Rhino.LastCreatedObjects
  If IsArray(aResults) Then
    ReDim aPoints(UBound(aResults))
    For i = 0 To UBound(aResults)
      aPoints(i) = Rhino.PointCoordinates(aResults(i))
    Next
    Call Rhino.DeleteObjects(aResults)
    RhIntersect = aPoints
  End If

  Call Rhino.UnselectObjects(aCurves)

End Function  

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' The one and only ExtractUVIntersectPts subroutine    
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Sub ExtractUVIntersectPts

  Dim sSurface, aCurves, aPoints, aObjects

  sSurface = Rhino.GetObject("Select surface", 24, True)
  If IsNull(sSurface) Then Exit Sub

  Call Rhino.EnableRedraw(False)
  aCurves = RhExtractWireframe(sSurface)
  If IsArray(aCurves) Then
    aPoints = RhIntersect(aCurves)
    Call Rhino.DeleteObjects(aCurves)
    If IsArray(aPoints) Then
      aObjects = Rhino.AddPoints(Rhino.CullDuplicatePoints(aPoints))
      Call Rhino.SelectObjects(aObjects)
    End If
  End If
  Call Rhino.EnableRedraw(True)

End Sub

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Rhino.AddStartupScript Rhino.LastLoadedScriptFile
Rhino.AddAlias "ExtractUVIntersectPts", "_NoEcho _-RunScript (ExtractUVIntersectPts)"