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

> 
> 
> 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.
> 

In that case:

http://www.gemology.ru/3dbook/eng/crypted/dif.html
seems like really detailed reflection data on diamonds, I wanted to use 
this, but apart from the 17% value that could I took from the graph, 
adjusting the exponent in an attempt to match this graph resulted in 
worse results.

Another page with some info also refers to the 17% value:

http://www.christian-bernard.com/diamonds/brildef.htm
little tidbits about a number of optical properties of diamonds.

Rob

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Rob Hoopman <rob### [at] tunanl> wrote in news:3d7a4f93$1@news.povray.org:

> In that case:
> 
> http://www.gemology.ru/3dbook/eng/crypted/dif.html
> seems like really detailed reflection data on diamonds, I wanted to
> use this, but apart from the 17% value that could I took from the
> graph, adjusting the exponent in an attempt to match this graph
> resulted in worse results.
> 
> Another page with some info also refers to the 17% value:
> 
> http://www.christian-bernard.com/diamonds/brildef.htm
> little tidbits about a number of optical properties of diamonds.

All taken into consideration, I had found everything (I believe) except
any mention of the reflection aspect of a diamond, this will surely help
a great deal.

Thanks

-- 
(MIKA) Marc Champagne
marcch.AT.videotron.DOT.ca
Montreal, CANADA

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Just a thaught, try setting the stones in a more typical environment, such
as a light well lit jewlers shop window tray (if if your feeling patient,
throw in a little focal blur)

I was trying jemstones myself a while back, but never managed to get
anything good enough to post, but looking at yours again now, I think that
might have been because the items were out of context

--
Rick

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Wonderfully done! Great.

The site Rob referred gives good data on the polarization effect of the
diamond.
 I'll appreciate it how I could incorporate the parallel and perpendicular
polarization data for the POV-Ray raytracing.

Jong

"Marc Champagne" <nos### [at] pleasecom> wrote in message
news:Xns### [at] 204213191226...
> Rob Hoopman <rob### [at] tunanl> wrote in news:3d7a4f93$1@news.povray.org:
>
> > In that case:
> >
> > http://www.gemology.ru/3dbook/eng/crypted/dif.html
> > seems like really detailed reflection data on diamonds, I wanted to
> > use this, but apart from the 17% value that could I took from the
> > graph, adjusting the exponent in an attempt to match this graph
> > resulted in worse results.
> >
> > Another page with some info also refers to the 17% value:
> >
> > http://www.christian-bernard.com/diamonds/brildef.htm
> > little tidbits about a number of optical properties of diamonds.
>
> All taken into consideration, I had found everything (I believe) except
> any mention of the reflection aspect of a diamond, this will surely help
> a great deal.
>
> Thanks
>
> --
> (MIKA) Marc Champagne
> marcch.AT.videotron.DOT.ca
> Montreal, CANADA

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"Jong" <jjk### [at] mmewhaackr> wrote in news:3d7d3898$1@news.povray.org:

> Wonderfully done! Great.
> 
> The site Rob referred gives good data on the polarization effect of
> the diamond.
>  I'll appreciate it how I could incorporate the parallel and
>  perpendicular 
> polarization data for the POV-Ray raytracing.
> 
> Jong

I will surely have a closer look!

-- 
(MIKA) Marc Champagne
marcch.AT.videotron.DOT.ca
Montreal, CANADA

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"Jong" <jjk### [at] mmewhaackr> wrote in news:3d7d3898$1@news.povray.org:

> Wonderfully done! Great.
> 
> The site Rob referred gives good data on the polarization effect of
> the diamond.
> I'll appreciate it how I could incorporate the parallel and
> perpendicular polarization data for the POV-Ray raytracing.

The site was http://www.gemology.ru/3dbook/eng/crypted/dif.html

Jong, how did you interpret these graphs, I'm having a hard time making
sense of them, any clue?

Marc

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