Hi,

I occasionally (usually to feed parameters to CSG macros where) need an
empty object.
(This means that the spatial extension is empty.) Consider the following
approaches:

    #declare No_object1 = box {0 0}
    #declare No_object2 = intersection {box {0 0} box {1 1}}
    #declare No_object3 = quadric {0 0 0 1}

The first is quite fast but actually not correct: The object contains
one point.
It might happen that a stray ray accidentally hits this point, causing
artefacts.
The second remedies the problem, but causes a

    Warning: Degenerate CSG bounding box (not used!).

which I dislike for aesthetical reasons. The third, which I currently
use,
is fine. But it has no bounding box either and hence uses as much time
as the second. I might add a bounding box to the third approach, but I
still hope there might be a more elegant solution.

Any suggestions?

  Mark Weyer

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