After taking a long hiatus from Pov (too long if you ask me :) I have
started actively creating scene for it again. My latest scene is one I am
proud of involving a simple scene of a bowling ball about ready to strike
pins. It looks quite nice, if I do say so myself :) but one problem I am
having is that I can't get the motion blur right.

My idea was to create a bunch of bowling balls adjusting the transparency
as it is blurred. This was my first use of a macro ever (Good Lord those
things are powerful!) and it worked...okay...but the biggest problems I
was having was that the blur didn't look believable. This, of course,
could be fixed by tuning my while loop. 

What can't be fixed, however, is that as you turn the ball transparent you
can see the hollow holes I made using a difference and some cylinders. So
my question, in a long winded nutshell, is how do I make the ball appear
whole as it gets more and more transparent?

Cheers,

Tim

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"Tim Soderstrom" <tig### [at] sticnet> wrote in message
news:pan### [at] sticnet...
> After taking a long hiatus from Pov (too long if you ask me :)

It has been a long time indeed. Welcome back :)

> What can't be fixed, however, is that as you turn the ball transparent you
> can see the hollow holes I made using a difference and some cylinders. So
> my question, in a long winded nutshell, is how do I make the ball appear
> whole as it gets more and more transparent?

About the only suggestion I can give is a link to the TAG Q&T -
http://tag.povray.org/povQandT/languageQandT.html#motionblur

Cheers,

Ken Tyler

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> My idea was to create a bunch of bowling balls adjusting the
> transparency as it is blurred. This was my first use of a macro ever
> (Good Lord those things are powerful!) and it worked...okay...but the
> biggest problems I was having was that the blur didn't look
> believable. This, of course, could be fixed by tuning my while loop. 

Hopefully you're already doing this, but remember to rotate the ball
rather than just translating it.
 
> What can't be fixed, however, is that as you turn the ball transparent
> you can see the hollow holes I made using a difference and some
> cylinders. So my question, in a long winded nutshell, is how do I make
> the ball appear whole as it gets more and more transparent?

I am not quite sure what you mean. Surely the idea is that you can see
the holes? If you mean the holes aren't becoming transparent when the
rest of the ball is, the solution is to put the transparent pigment on
the difference rather than the sphere; instead of:
difference {
  object {
    Sphere
    pigment { Transparent }
  }
  object { Cylinder1 }
  object { Cylinder2 }
  object { Cylinder3 }
}

do this:

difference {
  object { Sphere }
  object { Cylinder1 }
  object { Cylinder2 }
  object { Cylinder3 }
  pigment { Transparent }
}

Not sure if this is what you want; please ignore me if I'm stating the
obvious. Otherwise, I hope that helped.

Daniel

-- 
Misinformation followed us like a plague      You can beat us with wires
Nobody knew from time to time                You can beat us with chains
If the plans had changed         You can run out your rules but you know
   .: www.doublezero.uklinux.net :.   You can't outrun the history train

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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

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
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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Wow....at 17 hours a frame that's quite an endeavour! :) Oh well, thanks
fro the link (and description). That cleared things up considerably.

On Mon, 28 Jun 2004 08:17:42 -0400, Warp wrote:

> http://tag.povray.org/povQandT/misconceptions.html#motionblur

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