Wasn't it Thorsten Froehlich who wrote:
>In article <3bb0e726@news.povray.org> , "Marc-Hendrik Bremer" 
><Mar### [at] t-onlinede> wrote:
>
>> It reports something around 95.7 which is probably not too high with a
>> crackle-function in the Iso. But that max_gradient of 5 is too low in this
>> case. I don't know why dAWiDi thinks that the object is not complex enough
>> to go under 10 PPS.
>
>No, 95 sounds good for crackle.  So in summary the problem reported by
>"dAWiDi" <pov### [at] xxs-swpde> is a user error.  The suggested solution is
>to use an appropriate max_gradient and to read the documentation.

The symptoms don't sound anything remotely like the effects that
normally occur with an insufficient max_gradient.

There are max_gradient artefacts in the scene (tiny black holes near the
tips of the crackly bit) but they don't change significantly when the
render size is changed, and they certainly don't change at all between
the rendering of a partial scene and rendering the full scene.

I haven't yet tried rendering the full scene at 1024x768 AA, but I did
try ripping out some of the go-slow features of the scene to see if the
problem could be reproduced without the fog, the complicated sky pigment
and the reflective texture on the isosurface. The expected max_gradient
artefacts were visible, but nothing like the reported problem occurred.

The fact that changing max_gradient happens to fix it may well be
coincidental, in the same way that removing the sky, fog and reflection
happen to fix it.

-- 
Mike Williams
Gentleman of Leisure

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