In article <40bb89f8@news.povray.org> , Lutz-Peter Hooge <lpv### [at] gmxde> 
wrote:

> But what is the source of these differences?

Some POV-Ray features use pseudo-random numbers.  The sequence of these
numbers depends on the order of certain tracing calls.  If there is a small
computational difference in just one pixel POV-Ray may need to trace
additional rays (i.e. for anti-aliasing, but not limited to it*), you get a
butterfly effect when computing all consecutive pixels...

    Thorsten

* Chris Cason recently found that using jitter is very sensitive to the
butterfly effect.

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

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