Wasn't it Trevor G Quayle who wrote:
>"Roman Reiner" <lim### [at] gmxde> wrote:
>> I doubt raising the max_trace_level would help but you can give it a try. i
>> would recommend raising the max_gradient of the isosurface instead (a value
>> of 4 should work i guess). at least this always helped with my isosurfaces
>> ;-)
>>
>> Regards Roman
>
>"Roman Reiner" <lim### [at] gmxde> wrote:
>> I doubt raising the max_trace_level would help but you can give it a try. i
>> would recommend raising the max_gradient of the isosurface instead (a value
>> of 4 should work i guess). at least this always helped with my isosurfaces
>> ;-)
>>
>> Regards Roman
>
>I did some tests and found that max_gradient, adc_bailout, max_trace_level
>all have no effect on the outcome. Neither does moving the superellipsoid
>(except if you move it down so that it DOES intersect the plane).  This is
>true for both the superellipsoid and isosurface versions.  The only thing
>that I could change to remove the dots was reducing the ior value. In the
>end, I'm not sure what causes the dots, but perhaps this will help someone
>else identify the problem...

I stripped the problem down to a fairly minimal scene, to eliminate
anything to do with isosurface parameters, coincident surfaces, photon
artefacts, etc. and the dots are still there.

My guess is that they might possibly be real effects. The particular
shape of the superellipsoid causing infinite internal reflections.

If you set the max_trace_level to 100000, then there are fewer dots, and
the ones that are left turn red. That suggests to me that some rays are
getting trapped forever inside the object, becoming slightly redder with
each internal reflection.



global_settings {
     max_trace_level 24
}

background {rgb 1}
camera {
     location  <0.0, 1.5, -4.0>
     look_at   <0.5, 0.0,  0.0>
}

light_source {
     <200, 180, -200>                  
     color rgb 1
}
       

#declare gemmat=
material {
     texture {
          pigment {
               color rgbt <1,0,0,0.9>
          }
     }
     interior {
          ior 1.765                // Corundum
     }
}     


superellipsoid {
     <0.15, 0.15> 
     scale <0.6, 1, 0.25>
     rotate 15 * y
     translate z
     material {gemmat}
}

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