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"JEofVA" <jce### [at] attglobal net> wrote in message
news:web.486a9b1613f6a9318a187d850@news.povray.org...
> As the Subject says, I'm very new at this, and not sure what I'm doing
> wrong.
Welcome to the newsgroup.
> The image I am trying to render is one of a sphere of nested multi colored
> spheres with a wedge removed to reveal the inner layers. I get what I
> think I'm
> suppose to get, except the inner spheres are speckled with lots of black
> pixels.
This sounds like a very similar problem to the one discussed a couple of
weeks ago in the thread
http://news.povray.org/povray.newusers/thread/%3Cweb.48513efe78241c82b979a58c0%40news.povray.org%3E/
>
> I read the piece about coincident surfaces causing this effect, but if
> that is
> what the problem is, I don't know what surface needs moving.
>
I think it is indeed coincident surfaces. The cut surfaces of your Crust,
Mantle, OuterCore and InnerCore all align exactly.
Two alternative solutions are mentioned in the thread above. One is to
'difference' the next smaller sphere from each larger sphere (Subtract the
Mantle sphere from the Crust, the OuterCore sphere from the Mantle and the
InnerCore sphere from the OuterCore). The second is to just have one sphere
and use a color_map to give the shells different colours.
In this case there is also a simple third option and that is to move the
corner of the box that you are using to slice out the segments. If the Crust
box starts at <0,0,0> you can use 0.00001*<1,1,-1> for the Mantle box,
0.00002*<1,1,-1> for the OuterCore box and 0.00003*<1,1,-1> for the
InnerCore box. This tiny difference is enough to make sure that the cut
surfaces are no longer coincident.
Regards,
Chris B.
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