"TawnyOwl" <taw### [at] webde> wrote:
> > For the texture, you should start with a totaly transparent pigment: rgbt 1
> >
> > Next, the finish
> > finish{reflection{0,1 fresnel}conserve_energy ambient 0 diffuse 0.01}
> > You can add some specular or phong highlights. If speculat, use a low
> > roughness (<0.001), for phong, use a large (>500) phong_size value.
> >
> > Then, the all important interior:
> > The diamond is described as white with a bluish light green tint.
> >
> > interior{ior 2.5 distersion 1.02 fade_color<0.9, 0.1, 0.93>
> > fade_distance 1 fade_power 1}
> > Typical diamond ion and a fair amount of dispersion.
> > The colour comes from the material, not the surface.
> >
> > You should then render with some light_source. Adding an high dynamic
> > range environment can realy help.
> >
> >
> >
> > Alain
>
> Many, many thanks for your suggestions. I will try them in the next days and -
> of course - I will post my final settings here. At the moment I'm playing around
> with the diamond texture macro Bruno Cabasson gave here some years ago, but the
> stone looks not like a diamond, more like glass. May be it is because this stone
> is an very old one which is not cut after the rules of Marcel Tolkowsky. The
> shape (or cut) of the stones seems to be very important too. In this case I
> tried to model as close as possible, but the scratch from the Wikipedia is not
> exhaustive since the side-views seems to be taken not from angles differencing
> about 180 degrees. So I had to guess a little bit...
>
> And - as a response to Thomas - of course, the final scene will be my next entry
> to the TC-RTC.
>
> Thanks again and best regards,
> Michael

The matter is quiet interessting and small changes to the parameters in a given
lighting situation can change the general impression by far more as I learned
now. I tested all given diamond materials in the newsgroups and jugded that
Brunos were the best, just to have a starting point. At this moment I have'nt
really analysed his settings which are very close to Alains proposals, I know
now. But after analysing Brunos settings Alain's proposals gave me the hint,
that I was on the right track. With Alain's hint to test a HDRI-Environment,
which is really crucial, I put the stone into the "thekitchen.hdr" by Jaime
Vives Piqueres and yielded a good result with the help of two other
light_sources. At the moment I'm figuring around the necessary photon-settings
(and the positions of the light_sources) to gain an image near to the picture of
the sceptre of Catherine the Great in the Wikipedia. Just for the fun of it and
not for my next TC-entry. I cannot match the unkown ligthing but I can perhaps
meet similiar caustics.

Best regards,
Michael

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