Tanking an *Intersection* between
a *rgbf* *lathe* object
and an arbitrary object
results in only a few randomly distributed "reflective" pixels.

If you remove any of the highlighted (by *xxx*) conditions
above, the rendering is as expected.

replacing the intersection by "clipped_by" still leads to the
faulty? results.

***sth***




// Persistence Of Vision raytracer version 3.1 sample file.
// intersected rgbf lathe does not render properly (result is only a
sparse random pixel pattern)
// Win95 4.00.950B PII 300
// Povray 3.1e.msvc.win32 (PII optimized)
// File by Stefan Hahn


#include "colors.inc"

#declare eye = <-0.1,0.5,-0.1> ;
intersection {
   lathe {
      linear_spline 5
      <0.00,0>
      <0.025,0.01>
      <0.1,0.04>
      <0.2,0.0>
      <0.00,0>
      scale 0.1

      texture{pigment{color rgbf<1,1,1,0.9> }}
   }
   cylinder {-y,y,0.05}
}


plane { y, 0
   pigment {  checker  color White color Red scale 0.03     }
   finish{ambient 0.2 diffuse 0.6}
}

camera {
   angle 30
   location eye
   up <0, 0.5, 0> right <0.6666, 0, 0>
   look_at <0,0,0>
}



light_source { <10, 10, -100> colour White }

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On Thu, 24 Jun 1999 21:16:06 +0200, Stefan Hahn wrote:
>Tanking an *Intersection* between
>a *rgbf* *lathe* object
>and an arbitrary object
>results in only a few randomly distributed "reflective" pixels.

The problem, believe it or not, is coincident surfaces.   Moving
the plane just a tiny bit fixes it.  Why this only happens with 
the intersection and not all the time is an interesting question,
but one for which I don't have the answer.

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I was wrong in describing the problem in the previous posting:
a rgbf-lathe has black measles on its own
in the following simpler file, the problem is already observable
but not so pronounced as in the example from my previous posting

// Persistence Of Vision raytracer version 3.1 sample file.
// rgbf lathe does not render properly (result is only a sparse random
pixel pattern)
// Win95 4.00.950B PII 300
// Povray 3.1e.msvc.win32 (PII optimized)
// File by Stefan Hahn


#declare eye = <-1,5,-1> ;
   lathe {
      linear_spline 5
      <0.00,0>
      <0.025,0.01>
      <0.1,0.04>
      <0.2,0.0>
      <0.00,0>

      pigment{color rgbf<1,1,1,0.5> }
   }

//cosmetics only
plane { y, 0  pigment {  checker  color White color Red scale 0.03
}finish{ambient 0.2 diffuse 0.6}}
camera {angle 30 location <-1,5,-1>   up <0, 0.5, 0> right <0.6666, 0,
0> look_at <0,0,0> }
light_source { <10, 10, -100> colour White }

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On Thu, 24 Jun 1999 21:43:38 +0200, Stefan Hahn wrote:
>I was wrong in describing the problem in the previous posting:
>a rgbf-lathe has black measles on its own

Well, that answers my remaining question, then.  Move your cosmetic
plane and the problem should go away.

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Ron Parker wrote:
> 
> On Thu, 24 Jun 1999 21:43:38 +0200, Stefan Hahn wrote:
> >I was wrong in describing the problem in the previous posting:
> >a rgbf-lathe has black measles on its own
> 
> Well, that answers my remaining question, then.  Move your cosmetic
> plane and the problem should go away.

  Which is an elementary mistake many users make until they fully
understand the ins and outs of the program. I recommend discussing
these problems you are having in a different group before submitting
them as official bug reports. This will give you the benifit of finding
a possible solution or at least a confirmation by someone else prior
to reporting it here.

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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