Using transparent versions of the object does not give a correct result
for motion blur. Changing the transparency gives even a more incorrect
result.

  Imagine that you have a white dot on the black ball, and during the
time the "shutter is open" (which is what motion blur simulates) the
white dot moves on the "photo" so that it's at all times visible.
If the ball moves at constant speed (as the bowling ball would
approximately do), the white dot will be equally blurred along its
entire path. There's no place where the white dot is stronger and
clearer and other places where it's dimmer and more blurred.
  By changing the amount of transparency along the path you are getting
a completely wrong result in this matter.

  And besides, as I said already, using transparency does not give
any correct result in the first place. The object is opaque all the
time, even if it moves during the time the "shutter is open". Using
transparency would mean that by some magic the ball turns transparent
while it's moving.
  The fact that with transparency you get to see the interior parts of
the ball is not the only reason why it's inaccurate.

  There's currently no way in POV-Ray to get a correct effect. The only
thing you can do is to render a regular animation of your scene (which
is as long as the "shutter is open") and then average the images with
a third-party program.

  For more text, see
http://tag.povray.org/povQandT/misconceptions.html#motionblur

-- 
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N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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