Ron Parker <par### [at] my-dejanewscom> wrote:
: This looks like a bug.

  It may look like a bug, but certainly this is exactly how it works. It
may be an unwanted behaviour, but it's not a bug (ie. a programming mistake).

: So, I applied the inverse to the clipping object manually.  The result is 
: what you see on the right, the blue object.  I can't say I didn't expect 
: this result, for it is true that !(A & B) (the "correct" result) is not equal
: to (!A & !B)

  You are right. Logic rules say that !(A & B) equals to (!A | !B). We
would need a clipped_by which works like an union instead of the one that
works like an intersection.
  Perhaps povray should use a union-like clipped_by when it automatically
inverses a clipped object (and of course it should inverse the clipping
object too). But is this the wanted behaviour?

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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