Version: Rhino 4.0
Summary: Demonstrates how to create lines based on circle geometry using RhinoScript.

Can Rhino turn circles into straight lines?

Consider the following subroutine:

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 ' StraightenCircles.rvb -- September 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.
 
 Option Explicit
 
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 ' StraightenCircles
 ' Creates lines based on the circumferences of circles.
 ' Lines will be oriented based on the plane of the circle.
 
 Sub StraightenCircles
 
   Dim obj_list, obj 
   Dim length, plane, origin, xaxis
   Dim endpt, line
 
   obj_list = Rhino.GetObjects("Select circles to straighten", 4, True, True)
   If IsArray(obj_list) Then
 
     Call Rhino.EnableRedraw(False)
 
     For Each obj In obj_list
       If Rhino.IsCircle(obj) Then
         ' Gather data
         length = Rhino.CurveLength(obj)
         plane = Rhino.CurvePlane(obj)
         origin = plane(0)
         xaxis = plane(1)
         ' Calculate
         xaxis = Rhino.VectorUnitize(xaxis)
         xaxis = Rhino.VectorScale(xaxis, length)
         endpt = Rhino.PointAdd(origin, xaxis)
         line = Rhino.AddLine(origin, endpt)
         Call Rhino.SelectObject(line)
       End If
 
     Next
 
     Call Rhino.EnableRedraw(True)
 
   End If
 
 End Sub
 
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 Rhino.AddStartupScript Rhino.LastLoadedScriptFile
 Rhino.AddAlias "StraightenCircles", "_NoEcho _-RunScript (StraightenCircles)"