Well there's a few effects that look sort of like it's changing. Firstly it's a
fully 3d pattern so as we move round it we can see parallax within the shape.
This is distorted a little because the object is refractive. And the refraction
causes internal reflections which can faintly be seen in some places. Plus
there's reflections of the environment causing some more movement on the
surface.

So I expect what you've noticed is a combination of some of those effects. The
pattern certainly isn't actually moving.

-- 
Tek
www.evilsuperbrain.com

"Jim Kress" <pov### [at] kressworkscom> wrote in message
news:3fd28aa5@news.povray.org...
> Why does the agate pattern change (at the bottom) as a function of rotation
> angle?
>
> Jim
>
> "Tek" <tek### [at] evilsuperbraincom> wrote in message
> news:3fd0ecb2@news.povray.org...
> > All the posts in p.b.i inspired me...
> >
> > For ages I've been meaning to buy some interesting looking lumps of rock
> as
> > inspiration for CG, since a lot of these rocks have an appearance quite
> unlike
> > anything I've ever seen rendered. Well following all the nice sub-surface
> images
> > I decided to finally go and buy a couple of these things. This is my first
> > attempt to render one of them and it's come out pretty good.
> >
> > It's a piece of "red agate", so naturally I used pov's agate pigment :)
> I've
> > used 2 medias, one for scattering and one for absorption, so the
> absorbtion
> > isn't affected by the colour.
> >
> > ...And that's about all I can think of to say about it.
> >
> > Anyway, what do you think? :)
> > -- 
> > Tek
> > www.evilsuperbrain.com
> >
> >
> >
>
>

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