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On 09/23/2012 06:59 PM, Ive wrote:
> Am 23.09.2012 19:18, schrieb James Holsenback:
>>
>> LOL ... never mind I found a way to do it (still some tweaking left) . I
>> made the pigment in the material srgbf 0.85 and put some colored
>> emission media in the interior ... not exactly intuitive (to me anyways)
>
> This is not a good idea. A gemstone does absorb light and not emit it.
Yes this was a fail ... and after I thought about it for a bit I thought
the same thing.
> I've found this page with some spectral data for gemstones:
>
> http://www.octonus.com/oct/projects/adsorbtion_spectra.phtml
>
> and used this data to play a bit around with your stone. And after
> getting some strange effects I noticed that you have a coincident
> surface problem within the merge.
Yes it left a visible line shadow on the ground plane ... thought merge
would have gotten rid of coincident surface ( where the two cones met
before difference ) but obviously not ... hmmm
> This is exactly your gem shape but without coincident surface and it
> renders even a bit faster.
>
> #declare Gem = intersection {
> #local ndx = 0;
> #while ( ndx < 360 )
> plane {-x, 0 rotate z*-55 translate x*-2.75 rotate y*ndx }
> plane {-x, 0 rotate z*35 translate x*-2.75 rotate y*ndx }
> #local ndx = ndx + 45;
> #end
> plane {y, 0 translate y*1}
> }
way more elegant ... thanks
> And I would use something like this for gems:
>
> #macro M_Gem (Color, IOR, FadeDist)
> material {
> texture {
> pigment {rgb Color filter 1}
> finish {
> ambient 0 emission 0 diffuse 0
> reflection {0 1 fresnel on} conserve_energy
> }
> }
> interior {
> ior IOR
> fade_power 1001
> fade_distance FadeDist
> fade_power rgb < pow(Color.red,3),
> pow(Color.green,3)
> pow(Color.blue,3) >
> }
> }
>
> #end
>
>
> Note that I do usually use 1cm = 1 POV-Unit and in this case
> fade_distance 1 works pretty well. You have scaled your gem much
> bigger so you have to adjust fade_distance to fit your scale.
>
>
> Attached is a quick lo-quality (90 seconds) preview render - not a
> spectral one - featuring your stone: from left to right emerald,
> sapphire and amethyst.
>
> -Ive
Wow ... thanks for the macro and all the advise. I really appreciate it!
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