Rob Hoopman <rob### [at] tunanl> wrote in news:3d7a448a@news.povray.org:

> I only just now saw both your diamond renders. Especially these last
> ones look really good.
> I have to agree on what Jaime wrote, most images of brilliants I've
> seen look more like the image he linked than the one you posted.
> 
> 
> I was trying to do some brilliant cut diamonds two weeks ago and
> managed to google up some extra information:
> 
> The ior and dispersion settings should be correct, reflection is a bit
> off I think; I found information (don't have the link but can probably
> google it up again if you need it) that diamond reflects around 17% at
> a 0 degree incident angle and nearly 100% at a 90 degree angle.

I Agree, I was unable to find any info on reflection properties and
assumed that such a dense and highly polished stone would have a lot
of relfection.

A quote from the works of Marcel Tolkowsky, 1919:
| In a diamond, the amount of light reflected from the surface is much
| smaller than that penetrating into the stone ; moreover, a diamond is
| practically perfectly transparent, so that all the light that passes
| into the stone has to pass out again.  This is why lustre may be
| ignored in the working out of the correct shape for a diamond, and why
| any variation in the amount of light reflected from the exposed
| surface due to a change in that surface may be considered as
| negligible in the calculations 

> I don't know how much influence this has on the output image but I
> remember it made the my renders better after adjusting the reflection 
> settings, allthough it could be I fiddled with another knob and this
> had nothing to do with it.
> 
> I included an image of one of my renders ( I don't have the source for
> this exact scene any more as I continued to play around with it, but I
> still have the settings for the diamond texture, interior and finish)
> Mind you, I think your renders look a lot better, the colors in my 
> version are way to flat(?) and seems to be to harshly lit, but I do
> like the characteristic blue and yellow streaks (scintillation ?).
> 
> I hope this helps any and is not just a wast of bandwidth ;-).

I also googled quite a bit and coperniced also (to learn the art
of diamond cutting).

I'm getting close to my goal and all input is appreciated, thanks.

I will post the code soon enough.

MIKA

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