Hi
Can anybody tell me why I get a bright rim when I clip this CSG difference ?
Thanks for your help !

#version 3.7;
#include "colors.inc"
#include "math.inc"

global_settings { max_trace_level 256 assumed_gamma 1.0 }

camera {
    angle 1.25
    location <0, -50, -1000>
    look_at <0,10,0>
}

object { difference { sphere { 0, 15.01  }
                      sphere { 0, 15.0 }
                    }
         clipped_by { cone { 0, 0.0, <0,50,0>, 50*tand(45) } }
         pigment { rgbt 1 }
         hollow
         interior { media { emission 0.3*White } }
      }

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> Hi
> Can anybody tell me why I get a bright rim when I clip this CSG difference ?
> Thanks for your help !
>
> object { difference { sphere { 0, 15.01  }
>                        sphere { 0, 15.0 }
>                      }
>           clipped_by { cone { 0, 0.0,<0,50,0>, 50*tand(45) } }
>           pigment { rgbt 1 }
>           hollow
>           interior { media { emission 0.3*White } }
>        }
>
>

This object is used as a container for your media.
This object is NOT fully closed: clipped leaves the clipped part open.
You hit the first surface, you are now considered inside the object. The 
next surface encountered is the iner surface of the oposite side. The 
third surface is the outer surface. There is NO fourth surface, leading 
to an "infinite" path through your media.

Solution: DO NOT use clipped_by.

Change your object as follow:
object { difference { sphere { 0, 15.01  }
                       sphere { 0, 15.0 }// Makes your shell
                    // }
          //clipped_by { cone { 0, 0.0, <0,50,0>, 50*tand(45) } }
          cone { 0, 0.0, <0,50,0>, 50*tand(45) inverse}
// removes the part outside the cone and properly close the edge of the 
shell.
          }
          pigment { rgbt 1 }
          hollow
          interior { media { emission 0.3*White } }
       }



Alain

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Alain <aze### [at] qwertyorg> wrote:

> > Hi
> > Can anybody tell me why I get a bright rim when I clip this CSG difference ?
> > Thanks for your help !
> >
> > object { difference { sphere { 0, 15.01  }
> >                        sphere { 0, 15.0 }
> >                      }
> >           clipped_by { cone { 0, 0.0,<0,50,0>, 50*tand(45) } }
> >           pigment { rgbt 1 }
> >           hollow
> >           interior { media { emission 0.3*White } }
> >        }
> >
> >
>
> This object is used as a container for your media.
> This object is NOT fully closed: clipped leaves the clipped part open.
> You hit the first surface, you are now considered inside the object. The
> next surface encountered is the iner surface of the oposite side. The
> third surface is the outer surface. There is NO fourth surface, leading
> to an "infinite" path through your media.
>
> Solution: DO NOT use clipped_by.
>
> Change your object as follow:
> object { difference { sphere { 0, 15.01  }
>                        sphere { 0, 15.0 }// Makes your shell
>                     // }
>           //clipped_by { cone { 0, 0.0, <0,50,0>, 50*tand(45) } }
>           cone { 0, 0.0, <0,50,0>, 50*tand(45) inverse}
> // removes the part outside the cone and properly close the edge of the
> shell.
>           }
>           pigment { rgbt 1 }
>           hollow
>           interior { media { emission 0.3*White } }
>        }
>
>
>
> Alain

Sorry for asking such a stupid question ! Your reply is perfect,
and the explanation on the virtual infinite path perfectly clear.

And, as usual : "you never read deeply enough the manual" !
Thanks a lot !

And, by the way : is there some reason for the clipped objects beeing left open
by default in PovRay ?

Gilles

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43oasis <43o### [at] orangefr> wrote:
> And, by the way : is there some reason for the clipped objects beeing left open
> by default in PovRay ?

  clipped_by is faster to render than intersection.

-- 
                                                          - Warp

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Am 05.07.2011 09:00, schrieb 43oasis:

> And, by the way : is there some reason for the clipped objects beeing left open
> by default in PovRay ?

Yes: This way you can cut openings into otherwise solid primitives 
(making them non-solid shells). That's essentially the difference 
between clipped_by and difference (no pun intended).

Post a reply to this message

clipka <ano### [at] anonymousorg> wrote:
> Am 05.07.2011 09:00, schrieb 43oasis:
>
> > And, by the way : is there some reason for the clipped objects beeing left open
> > by default in PovRay ?
>
> Yes: This way you can cut openings into otherwise solid primitives
> (making them non-solid shells). That's essentially the difference
> between clipped_by and difference (no pun intended).

Thanks !
Gilles

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Warp <war### [at] tagpovrayorg> wrote:
> 43oasis <43o### [at] orangefr> wrote:
> > And, by the way : is there some reason for the clipped objects beeing left open
> > by default in PovRay ?
>
>   clipped_by is faster to render than intersection.
>
> --
>                                                           - Warp

Thanks !
And : this RC3 is great on quad-core system !
Gilles

PS : what a pity the Special Relativity patch (Leo Brewin, 2005) was not
integrated into the official PovRay ; it would have been a real plus to this
fantastic software, for educational purposes (my case).
But that is an old story, I guess it was not as simple as "just plug it in" ...

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