In POV-Ray 3.7, a transparent sphere_sweep using a B-sline or a cubic spline
sometimes shows a disc at the endcaps.  (Note also that in this particular
example, the artifact on the right end does not cast a shadow, but on the left
end, a shadow is cast even though the artifact barely shows in the sphere_sweep
itself.)  Is this a known bug?

The artifact does NOT show for linear_spline.

The artifact does NOT show in POV-Ray 3.5 or 3.6.1.
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global_settings { assumed_gamma 1 }

camera
{ location <-2.8356, 1.0000, -4.9115>
  look_at <0, 1, 0>
  angle 38.8508
}

light_source { <-3.3125, 7.6250, -5.7374>, rgb 1 }

box
{ -<7, 0, 7>, <7, 9, 7> hollow
  pigment { rgb 1 }
}

sphere_sweep
{ cubic_spline 4,
  <-3, 1.5, 0>, 0.4,
  <-1, 0.5, 0>, 0.4,
  <1, 1.5, 0>, 0.4,
  <3, 0.5, 0>, 0.4
  pigment { red 1 transmit 0.5 }
}
__________________________________________________

POV-Ray version: 3.7.RC7
Operating System: openSUSE 12.2 Linux
CPU: Dell Inspiron 17R, Intel Core i7

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Am 02.06.2013 18:03, schrieb Cousin Ricky:
> In POV-Ray 3.7, a transparent sphere_sweep using a B-sline or a cubic spline
> sometimes shows a disc at the endcaps.  (Note also that in this particular
> example, the artifact on the right end does not cast a shadow, but on the left
> end, a shadow is cast even though the artifact barely shows in the sphere_sweep
> itself.)  Is this a known bug?

3rd order (i.e. cubic and similar) spline sphere sweeps are known to 
have serious math issues, so I'm not at all surprised.

Someone needs to re-work the whole 3rd order sphere sweep math sooner or 
later.

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