See
http://news.povray.org/povray.general/message/%3C5682b65f%241%40news.povray.org%3E/

This artifact rears its ugly head when merging a torus and a cylinder into a
very fat discus-like object.  See p.b.i for an illustration.

I thought surely I had discovered this problem while I was fiddling with the
meniscus code for CoffeeMug in 2013.  But checking the dates on my test files,
it turns out I'd discovered it in 2008, a mere three days after starting work on
RoundEdge.  (I'm not too surprised at this recall failure; meat-based brains are
known to be unreliable.)

I almost immediately realized why my torus-cylinder merges showed this artifact,
which is why I never reported this as a bug.  But bug or not, it is annoying, so
it is fixed in RoundEdge 1.3.1.

http://lib.povray.org/searchcollection/index2.php?objectName=RoundEdge&contributorTag=Cousin%20Ricky

Why I didn't take steps to correct the problem in RoundEdge 1.0 is a mystery.
Another meat brain failure, perhaps?

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Am 25.01.2016 um 19:15 schrieb Cousin Ricky:

> I almost immediately realized why my torus-cylinder merges showed this artifact,
> which is why I never reported this as a bug.  But bug or not, it is annoying, so
> it is fixed in RoundEdge 1.3.1.

... and it is also fixed (kind of, that is) in POV-Ray 3.7.1 ;)

You may want to change your RE__torus macro as follows:


#macro RE__torus (RMajor, rMinor, Use_merge)
  #if (RMajor * 2 < rMinor & Use_merge)
    #if (RoundEdge_Inc_Temp >= 3.7.1)
      torus { RMajor, rMinor merge }
    #else
      merge
      { difference
        { torus { RMajor, rMinor }
          sphere { 0, re_R }
        }
        sphere { 0, (re_R + rMinor) / 2 }
      }
    #end
  #else
    torus { RMajor, rMinor }
  #end
#end


Specifying the "merge" keyword after the major & minor radii of a torus
will cause interior surfaces of a spindle torus to be suppressed.

The "difference", "intersection" and "union" keywords also work there as
you might expect (though "union" is only included for completeness, as
it's the default anyway).

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