If, in the scene below, I change the y-axis rotation from 90 to 91 deg.
POV-Ray mentions "creating bounding slabs" and goes on with that forever. At
90 deg it traces in a few seconds.

What is it that happens here?


ingo

----
#version 3.1;
#include "colors.inc"
global_settings {
    assumed_gamma 1.0
}

light_source {<500,200,-500> rgb 1}
camera {
    location  <0.0, 3.0,-20.0>
    look_at   <0.0, 3.0, 0.0>
    angle 35
}

#macro Spits(n,r)
  #local l=r*2;
  #local Tz=0;
  #while (n >=0)
    #local ru= (0.5*l)/sin(radians(180/n));
    #local Count=0;
    #local Rot=0;
    #while (Count<=n+1)
      sphere{
        <0,0,0>,r
        translate <(cos(radians(Rot)))*ru,(sin(radians(Rot))*ru),Tz>
      }
      #local Rot=Rot+(360/n);
      #local Count=Count+1;
    #end
    #local n=n-3;
    #local Tz=Tz-0.25;
  #end
#end

object{
  union{Spits(33,0.2)}
  rotate<90,90,0>      // Change to rotate<90,91,0>
  pigment{White}
}

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I didn't get the problem on my Macintosh... I'd guess there's a bug or a
conflict somewhere.

-Mark R.

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I should have mentioned, I'm using Win NT4-sp3.
The problem also occurs if I take away the rotation completely.
If I chage #local n=n-3 to #local n=n-2, everything seems to be ok.

ingo


Mark Radosevich heeft geschreven in bericht
<364F6125.597C7A32@randolph.spa.edu>...
>I didn't get the problem on my Macintosh... I'd guess there's a bug or a
>conflict somewhere.
>
>-Mark R.

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ingo wrote:
> 
> If, in the scene below, I change the y-axis rotation from 90 to 91 deg.
> POV-Ray mentions "creating bounding slabs" and goes on with that forever. At
> 90 deg it traces in a few seconds.
> 
> What is it that happens here?
> 
> ingo
> 
> ----
> #version 3.1;
> #include "colors.inc"
> global_settings {
>     assumed_gamma 1.0
> }
> 
> light_source {<500,200,-500> rgb 1}
> camera {
>     location  <0.0, 3.0,-20.0>
>     look_at   <0.0, 3.0, 0.0>
>     angle 35
> }
> 
> #macro Spits(n,r)
>   #local l=r*2;
>   #local Tz=0;
>   #while (n >=0)
>     #local ru= (0.5*l)/sin(radians(180/n));
>     #local Count=0;
>     #local Rot=0;
>     #while (Count<=n+1)
>       sphere{
>         <0,0,0>,r
>         translate <(cos(radians(Rot)))*ru,(sin(radians(Rot))*ru),Tz>
>       }
>       #local Rot=Rot+(360/n);
>       #local Count=Count+1;
>     #end
>     #local n=n-3;
>     #local Tz=Tz-0.25;
>   #end
> #end
> 
> object{
>   union{Spits(33,0.2)}
>   rotate<90,90,0>      // Change to rotate<90,91,0>
>   pigment{White}
> }

The only problem I could discover was your line "#while (n >=0)"
followed by "#local ru= (0.5*l)/sin(radians(180/n));".  If n starts as a
multiple of 3, and hence reaches 0, POV-Ray will crash while parsing
when it encounters the attempt to divide 180 by zero.  Changing the
n >=0 to n >0 fixed that problem, after which I had no trouble rendering
with rotate <90, 91, 0> applied to the finished object (on POV-Ray 3.1
and 3.1a for DOS, nor 3.1a for Windows).

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Chris Colefax heeft geschreven in bericht
<3651211E.2B3BB980@geocities.com>...
>The only problem I could discover was your line "#while (n >=0)"
>followed by "#local ru= (0.5*l)/sin(radians(180/n));".  If n starts as a
>multiple of 3, and hence reaches 0, POV-Ray will crash while parsing
>when it encounters the attempt to divide 180 by zero.  Changing the
>n >=0 to n >0 fixed that problem, after which I had no trouble rendering
>with rotate <90, 91, 0> applied to the finished object (on POV-Ray 3.1
>and 3.1a for DOS, nor 3.1a for Windows).
>

Aahum,   "#local ru= (0.5*l)/sin(radians(180/n));" I never looked at this
line. Being to fixated on the rotation. Thanks Chris.

Leaves me with one question: Why did it render with a rotation <90,90,0>?
Is this the magic of POV-Ray?

ingo

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