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  opal (Message 1 to 8 of 8)  
From: stbenge
Subject: opal
Date: 12 Sep 2009 19:29:26
Message: <4aac2ed6@news.povray.org>
Hello,

Here's my attempt at recreating an opal. It's not physically accurate.

It's a mesh stone shape, with many mesh inclusions. Each inclusion is a 
disc-shaped chip, colored randomly, and given a specular highlight with 
a metallic value of one to really bring out the color. They were placed 
randomly. The ones residing inside the stone were rendered, the rest 
were not.

Funny thing, the luminous bloom pass took longer to complete than the 
initial render itself. For some reason the black parts of the HDR image 
were the slowest. It could be an error in my code...

Sam


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From: Mike Raiford
Subject: Re: opal
Date: 12 Sep 2009 19:37:59
Message: <4aac30d7$1@news.povray.org>
stbenge wrote:

> It's a mesh stone shape, with many mesh inclusions. Each inclusion is a 
> disc-shaped chip, colored randomly, and given a specular highlight with 
> a metallic value of one to really bring out the color. They were placed 
> randomly. The ones residing inside the stone were rendered, the rest 
> were not.

I was wondering how you could simulate the fire effect that opals have. 
Very tough thing to simulate in CG, if you ask me. I've not attempted 
this, but I have given it some thought.

BTW, I built a nice list of dispersion and IOR values for many types of 
gemstones/minerals. Does anyone think this could be of utility at all?


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From: stbenge
Subject: Re: opal
Date: 12 Sep 2009 20:59:13
Message: <4aac43e1$1@news.povray.org>
Mike Raiford wrote:
> stbenge wrote:
> 
>> It's a mesh stone shape, with many mesh inclusions. Each inclusion is 
>> a disc-shaped chip, colored randomly, and given a specular highlight 
>> with a metallic value of one to really bring out the color. They were 
>> placed randomly. The ones residing inside the stone were rendered, the 
>> rest were not.
> 
> I was wondering how you could simulate the fire effect that opals have. 
> Very tough thing to simulate in CG, if you ask me. I've not attempted 
> this, but I have given it some thought.

To model it accurately would require more time than we have, I think. We 
might be able to place hollow inclusions within the stone which have a 
regular surface normal (like "quilted" or "leopard"), and add dispersion 
on top of that.

> BTW, I built a nice list of dispersion and IOR values for many types of 
> gemstones/minerals. Does anyone think this could be of utility at all?

There is already such a utility called NewIOR.INC by Sven-Erik Andersen. 
I use it a reference, since I like to build my materials myself. But if 
you can improve on it (and maybe implement a birefringence model), then 
I'll take a look at it. I still haven't rendered calcite :)

Sam


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From: Carlo C 
Subject: Re: opal
Date: 13 Sep 2009 08:45:00
Message: <web.4aace8b9c0d9bbcfbcad4c690@news.povray.org>
stbenge <not### [at] hotmailcom> wrote:
> Hello,
>
> Here's my attempt at recreating an opal. It's not physically accurate.
>
> It's a mesh stone shape, with many mesh inclusions. Each inclusion is a
> disc-shaped chip, colored randomly, and given a specular highlight with
> a metallic value of one to really bring out the color. They were placed
> randomly. The ones residing inside the stone were rendered, the rest
> were not.
>
> Funny thing, the luminous bloom pass took longer to complete than the
> initial render itself. For some reason the black parts of the HDR image
> were the slowest. It could be an error in my code...
>
> Sam

Wonderful effect!

-
(Obviously, if accidentally, or recklessly, you post the source, you make
someone really happy...)
-


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From: stbenge
Subject: Re: opal
Date: 13 Sep 2009 18:32:05
Message: <4aad72e5$1@news.povray.org>
Carlo C. wrote:
> Wonderful effect!

Thanks!

> (Obviously, if accidentally, or recklessly, you post the source, you make
> someone really happy...)

It might have somehow ended up in p.b.scene-files, maybe even at this 
location: news://news.povray.org:119/4aad7250@news.povray.org

Sam


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From: Carlo C 
Subject: Re: opal
Date: 14 Sep 2009 05:05:00
Message: <web.4aae0727c0d9bbcf28b91d190@news.povray.org>
stbenge <not### [at] hotmailcom> wrote:
> Carlo C. wrote:
> > Wonderful effect!
>
> Thanks!
>
> > (Obviously, if accidentally, or recklessly, you post the source, you make
> > someone really happy...)
>
> It might have somehow ended up in p.b.scene-files, maybe even at this
> location: news://news.povray.org:119/4aad7250@news.povray.org
>
> Sam

Even with the comments!
Oh, Thank you!


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From: Paolo Gibellini
Subject: Re: opal
Date: 15 Sep 2009 07:56:40
Message: <4aaf80f8@news.povray.org>
>stbenge  on date 13/09/2009 01:29 wrote:
> Hello,
> 
> Here's my attempt at recreating an opal. It's not physically accurate.
> 
> It's a mesh stone shape, with many mesh inclusions. Each inclusion is a 
> disc-shaped chip, colored randomly, and given a specular highlight with 
> a metallic value of one to really bring out the color. They were placed 
> randomly. The ones residing inside the stone were rendered, the rest 
> were not.
> 
> Funny thing, the luminous bloom pass took longer to complete than the 
> initial render itself. For some reason the black parts of the HDR image 
> were the slowest. It could be an error in my code...
> 
> Sam
> 
> ------------------------------------------------------------------------
> 
Fine.
Other inspirations for you:
http://minerals.caltech.edu/Silica_Polymorphs/index.html
;-)
Paolo


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From: stbenge
Subject: Re: opal
Date: 15 Sep 2009 16:13:10
Message: <4aaff556@news.povray.org>
Paolo Gibellini wrote:
> Fine.
> Other inspirations for you:
> http://minerals.caltech.edu/Silica_Polymorphs/index.html
> ;-)
> Paolo

Thanks, Paolo! Great page :)


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