Nieminen Mika wrote:

>   No, it's not a bug. Povray works perfectly. How do you expect povray to
> know which one of the coincident planes is at the most top?

No.   It is a bug.

It is a simple fact of algebra that any object minus itelf equals zero,
or null.  In POV this is not the case.  Therefore it is a bug.

Does (sqrt 2)^2 - 2 = 0?  Is 3 * (1/3) - 1 = 0?  Of course.  But computers
may not yield these results.

There is no ambiguity in the case of difference.

Now in the case of union, I agree with you.

Dan

P.S. Just because it is a bug doesn't mean it should be fixed, as
the problem is with the way computers represent floating point numbers,
and thus isn't something which POV should try to correct.

-- 
http://www.flash.net/~djconnel/

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