Hello,

I'm now looking at splines and trying to understand how POVRay treats
this object.

I made a trace in Inkscape and exported it to POV.
Export looks like this :

#declare path35 = prism {
 linear_sweep
 bezier_spline
 1.0, //top
 0.0, //bottom
 12 //nr points
 /*   0*/ <249.99999874, 886.42857827>, <316.34878488, 854.35384819>,
          <403.57141417, 756.42857575>, <312.85712126, 640.71428031>,
 /*   1*/ <312.85712126, 640.71428031>, <222.14285480, 525.00000000>,
          <128.57142803, 566.42857323>, <109.28570835, 735.00000000>,
 /*   2*/ <109.28570835, 735.00000000>, <90.00000000, 903.57142677>,
          <183.65121260, 918.50330457>, <249.99999874, 886.42857827>
 }


If I've understood correctly, each line has 4 vectors :
- the point,
- control point 1,
- control point 2,
- next point.

So i thought the two control points were the handle points.
So I tried to draw it all. This is the attached image.
Left: Inkscape screenshot, Right : POV

And it doesn't quite work as expected :
- square for principal points are (seems) OK
- first handle seems OK (with fine lines)
- second handles are wrongs (with heavy lines) :(


* Doesn't the third vector represent the second control point ?
* It also seems strange to me that the fourth vector is equal to the
  next main point.


There are a few things I didn't understand.
Is there a doc, a web page, ... that explains POV splines
in more detail ?



Thanks

-- 
Kurtz le pirate
Compagnie de la Banquise

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