Semi-inspired by my recent rendering, I'm creating a set of macros to 
generate cut gems. Also, at one point waaaay back in the past, someone 
made a post of diamonds modeled in a piece of software called GemCad. I 
wanted to do something like that, but do it differently:

Pure CSG Diamonds.

So, Here are a couple cuts from a class of cuts called "Old European"

On the left is a Table Cut. Nothing exciting, basically follows the 
natural shape of a diamond. On the right is an Old Single Cut with two 
different parameters. Neither of these are the well-known brilliant cut, 
though the Old Single cut may very well be the basis for the brilliant 
cut, since it already has all of the proper angles.

There are 2 renders: One with a basic material so you can better see the 
shape of the facets, and one with a diamond-like material, complete with 
photons.

The next cuts I'll probably tackle are Eight cut, Emerald and Step cut-- 
since these are relatively simple. Eight cut may be a bit slightly 
challenging because the facets are rounded at the edges, but I might be 
wrong, it could be very simple, especially if the stone has a girdle.

I'm learning all sorts of terminology with this project:

The top "half" is the crown of the gem, the flat facet at the top is 
called the table, the bottom "half" is the pavilion, and space between 
the crown and pavilion is called the girdle, if it exists. At the bottom 
of the pavilion there can be one more facet, called the cullet, or the 
pavilion can come to a point.

I still need to work on cut depth, as well ( which determines the angles 
in the pavilion )

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Attachments:
Download 'make_gemstone.jpg' (145 KB) Download 'make_gemstone_basic.jpg' (152 KB)

Preview of image 'make_gemstone.jpg'

Preview of image 'make_gemstone_basic.jpg'

Truly shiny.  But such small pieces truly demand some focal blur to appear
realistic!  Yes, I realize it may already have been hard enough with all the
refractions, caustics and dispersion... :P

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What's your max_trace_level?  I find that I need an insanely high value high
value for this sort of thing--at least 60 to 100 to get rid of the visibly dark
areas.  Sometimes tracing doesn't bail even after 256, although at this point it
doesn't make much visual impact.

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On Sat, 05 Sep 2009 23:50:21 -0400, Mike Raiford  
<mraXXXiford.at.@g1023mail.com> wrote:

> On the left is a Table Cut. Nothing exciting, basically follows the
> natural shape of a diamond. On the right is an Old Single Cut with two
> different parameters. Neither of these are the well-known brilliant cut,
> though the Old Single cut may very well be the basis for the brilliant
> cut, since it already has all of the proper angles.

I did a brilliant round cut a few years ago, but was never satisfied with  
the results.  They just never had the level of sparkle that I see in real  
diamonds.  Looking at the light traces, I suspect that my parameters may  
be suboptimal.  (I got the parameters from a Web site that appears to have  
passed on.)

I also suspect a bug (feature?) in dispersion: renders seem to be darker  
than without dispersion.  It just occurred to me that the multiple  
reflections and refractions in a cut gem could possibly exacerbate the  
problem.

I know Chris B. will show up to buttonhole us any second now, so I'll just  
say that I've been shy about submitting this, because of my  
dissatisfaction of the sparkle, but also because I fear that, with just  
the one cut, the module lacks generality.


-- 
<Insert witty .sig here>

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Attachments:
Download 'diamond0-lo.jpg' (5 KB) Download 'diamond0-hi.jpg' (6 KB) Download 'diamond-demo-c.png' (33 KB) Download 'diamond_b90.png' (63 KB) Download 'diamond_b75.png' (130 KB)

Preview of image 'diamond0-lo.jpg'

Preview of image 'diamond0-hi.jpg'

Preview of image 'diamond-demo-c.png'

Preview of image 'diamond_b90.png'

Preview of image 'diamond_b75.png'

Very sparkly!
Are you working towards just certain cuts, or any arbitrary stone
cutting instruction set? I stopped pursuing an instruction parser, but
seeing these pictures I will have to start again.

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"Cousin Ricky" <ric### [at] yahoocom> wrote in message 
news:op.### [at] your-727a0a4e7cvipowernetnet...
>
> I know Chris B. will show up to buttonhole us any second now

I think you may be confusing me with someone else, but if it really is me 
you're targetting with this comment I'd appreciate an explanation. I don't 
think that I've done anything to offend you (or hopefully anyone else for 
that matter). If there is something you would prefer to discuss privately, 
feel free to drop me a line at Chris.Bartlett2 on the server virgin.net.

Chris B.

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On Sun, 6 Sep 2009 09:20:38 +0100, "Chris B" <nom### [at] nomailcom> wrote:

>
>"Cousin Ricky" <ric### [at] yahoocom> wrote in message 
>news:op.### [at] your-727a0a4e7cvipowernetnet...
>>
>> I know Chris B. will show up to buttonhole us any second now
>
>I think you may be confusing me with someone else, but if it really is me 
>you're targetting with this comment I'd appreciate an explanation.

It must be awe ;)
You are never anything but helpful except maybe knowledgeable :D
BTW that is a complement.
-- 

Regards
     Stephen

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"Stephen" <mcavoysAT@aolDOTcom> wrote in message 
news:mav6a59adkgch33h2jpnd0gmgsq4stjhpf@4ax.com...
> On Sun, 6 Sep 2009 09:20:38 +0100, "Chris B" <nom### [at] nomailcom> wrote:
>
>>
>>"Cousin Ricky" <ric### [at] yahoocom> wrote in message
>>news:op.### [at] your-727a0a4e7cvipowernetnet...
>>>
>>> I know Chris B. will show up to buttonhole us any second now
>>
>>I think you may be confusing me with someone else, but if it really is me
>>you're targetting with this comment I'd appreciate an explanation.
>
> It must be awe ;)
> You are never anything but helpful except maybe knowledgeable :D
> BTW that is a complement.
> -- 


Thanks Stephen,

TBH I wasn't sure what "to buttonhole" meant when I first saw it. The trusty 
Internet delivered the definition of "to detain (a person) in conversation 
against their will" which left me feeling a little offended, but also 
between a rock and a hard place. I wouldn't want such an accusation to go 
unchallenged, but pursuing the matter will almost certainly  make me guilty 
of engaging someone in a conversation they probably don't want to have. 
Don't you just hate those tricky situations :o)

Regards,
Chris B.

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Cousin Ricky wrote:
> What's your max_trace_level?  I find that I need an insanely high value high
> value for this sort of thing--at least 60 to 100 to get rid of the visibly dark
> areas.  Sometimes tracing doesn't bail even after 256, although at this point it
> doesn't make much visual impact.
> 

50 but yeah... it went all the way to 50. I'm trying it with 255 to see 
if there's a difference.

Post a reply to this message

Cousin Ricky wrote:
> What's your max_trace_level?  I find that I need an insanely high value high
> value for this sort of thing--at least 60 to 100 to get rid of the visibly dark
> areas.  Sometimes tracing doesn't bail even after 256, although at this point it
> doesn't make much visual impact.
> 

Oh, and I think some of it may be the black "sky" that it's refracting...

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