title: How do I create a Bezier curve to represent a smoothed polyline?
body: <p>I have a polyline that approximates a curve, and I want to draw it as a smooth curve in PostScript, which supports Bezier curve drawing. To do that, I need to generate two control points between each pair of polyline points. (I can't get the original curve from the source, just the polyline.) </p>
  
  <p>I've had some success using cardinal splines from <a href="http://www.ibiblio.org/e-notes/Splines/Cardinal.htm" rel="noreferrer">this description</a>, but the parameters there are different from <a href="http://en.wikipedia.org/wiki/Cubic_Hermite_spline" rel="noreferrer">Wikipedia</a> and <a href="http://msdn.microsoft.com/en-us/library/ms536358%28VS.85%29.aspx" rel="noreferrer">GDIPlus.DrawCurve</a>, both of which refer to tension. MS has no details, and Wikipedia has incomplete details (cardinal spline ignores x values?).</p>
  
  <p>What are the formulas for the control points based on tension?</p>