Right - 'Cushion' or 'Octagonal' shape.

 Left - 'Pear' shape.

 Bottom - 'Star-cut' or Pentagon shape.

Photons are on, where's the pretties??  :(

   ~Steve~

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Attachments:
Download 'diam.jpg' (83 KB)

Preview of image 'diam.jpg'

You're using the correct IOR for diamond, right?  I don't have access to
any real diamonds to test this (oddly enough), but I don't think they
show much in the way of caustics.  A quick test with pov seems to
confirm this - try rendering the example scene straight from the Insert
menu, then try it again with an IOR of 2.47.  The bright spots on the
ground certainly don't look so neat.

Also, (I might just be making this up here) I think that the diamond
cuts are designed to reflect light back out towards the "user" :)  In
other words, all the sparkle comes straight back at you when you look at
them set in a ring, hence their sparkly appeal.

On a seperate note, where did you get the geometry?  And are they meshes
or CSG?  I've only ever found CSG versions of povray diamonds, and I
didn't have much luck turning up a geometrical description of a cut
detailed enough to make a mesh from when I searched.

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"Andrew" <ast### [at] hotmailcom> wrote in message
news:3e722e53$1@news.povray.org...
> You're using the correct IOR for diamond, right?  I don't have
access to
> any real diamonds to test this (oddly enough), but I don't think
they
> show much in the way of caustics.  A quick test with pov seems to
> confirm this - try rendering the example scene straight from the
Insert
> menu, then try it again with an IOR of 2.47.  The bright spots on
the
> ground certainly don't look so neat.

    Hiya Andy, are you seeing something different to me then? The only
bright spots I see are the reflections from the table surface. I'm
using most of Jurgen Sharfys' code and his IOR is 2.41.

    I'll give 2.47 a try.

  My caustics are low at the moment, I'm using .3 - I tried higher but
I thought the stones looked TOO colourful.

>
> Also, (I might just be making this up here) I think that the diamond
> cuts are designed to reflect light back out towards the "user" :)
In
> other words, all the sparkle comes straight back at you when you
look at
> them set in a ring, hence their sparkly appeal.

      You might be right with this image. I turned reflection off.

      Should I try turning refraction off and reflection on then? What
do you think? This image took around 1.5 hours at 640x480 aa 0.3, and
then I cut it a little.



>
> On a seperate note, where did you get the geometry?  And are they
meshes
> or CSG?  I've only ever found CSG versions of povray diamonds, and I
> didn't have much luck turning up a geometrical description of a cut
> detailed enough to make a mesh from when I searched.

   'Ere guvnor... wanna know a secret?  ;)  They're meshes. Have you
got a prog that can convert .dxf files to .pov? I used freeby Rhino.
Go here: www.gemcad.com (free 30 day trial), save as a .dxf, and then
open (whatever prog), and convert to a.pov file. The great thing with
gemcad is that you can alter the amount of facets you might want with
a click (I don't work for them!) - although I haven't tried this in
this image.

Have a play, it's fun. Looking forward to seeing something better than
mine (which won't be difficult!!)

      ;)

   ~Steve~



>
>

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> "Andrew" <ast### [at] hotmailcom> wrote in message
> news:3e722e53$1@news.povray.org...
> > You're using the correct IOR for diamond, right?  I don't have
> access to
> > any real diamonds to test this (oddly enough), but I don't think
> they
> > show much in the way of caustics.  A quick test with pov seems to
> > confirm this - try rendering the example scene straight from the
> Insert
> > menu, then try it again with an IOR of 2.47.  The bright spots on
> the
> > ground certainly don't look so neat.
>
>     Hiya Andy, are you seeing something different to me then? The only
> bright spots I see are the reflections from the table surface. I'm
> using most of Jurgen Sharfys' code and his IOR is 2.41.
>
>     I'll give 2.47 a try.
>
>   My caustics are low at the moment, I'm using .3 - I tried higher but
> I thought the stones looked TOO colourful.


Sorry - I think you've misunderstood me here, probably because I didn't
make
myself very clear to start with :)

What I mean to say was:  Open Pov, create a new file, use the menu item
Insert >> Scene templates >> Photons scene.  First render it straight
away.
Then change the ior of the glass to 2.47 (or whatever diamond really is)
and
re-render.  You'll see that the bright spots on the ground are no longer
bright.  This could be the problem with your diamonds.  Have you tried
setting the ior to 1.5 or so, just to see what a glass "fake" would look
like?

Thanks for the heads-up on gemcad - sounds useful.  Very useful in fact!

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Check this pic, I did it a week ago with the pear shape and it completely
sucks. Among other things, something went completely wrong with the
dispersion and I just couldn't get it working. And I decided to forget about
the thing anyways.

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Attachments:
Download 'freaking_pear.jpg' (79 KB)

Preview of image 'freaking_pear.jpg'

If you want diamonds to look like diamonds do and if you also want to use
the right shapes, your IOR should be set to the diamond's.

And for those interested in more info and dxf files, go to
http://www.3dlapidary.com/

Post a reply to this message

On Fri, 14 Mar 2003 23:28:11 +0100, Apache wrote:

> Check this pic, I did it a week ago with the pear shape and it completely
> sucks. Among other things, something went completely wrong with the
> dispersion and I just couldn't get it working. And I decided to forget about
> the thing anyways.

You're getting those little cyan spots too? WHat OS did you render this 
under? It seems like some sort of a bug in the windows compile of POV. By 
downloading the source and re-compiling POV under VC++ I could fix this bug 
(no changes to the source). I made a post to p.p a little while ago about 
this.

-- 
light_source#macro G(E)sphere{z+E*y*5e-3.04rotate-z*E*6pigment{rgbt#end{
20*y-10#local n=162;1}#while(n)#local n=n-.3;G(n)x}}G(-n).7}}#end//GregE

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"Andrew" <ast### [at] hotmailcom> wrote in message
news:3e723da3@news.povray.org...
> > "Andrew" <ast### [at] hotmailcom> wrote in message
> > news:3e722e53$1@news.povray.org...

> > > You're using the correct IOR for diamond, right?

> Then change the ior of the glass to 2.47 (or whatever diamond really
is)
> and
> re-render.  You'll see that the bright spots on the ground are no
longer
> bright.  This could be the problem with your diamonds.  Have you
tried
> setting the ior to 1.5 or so, just to see what a glass "fake" would
look
> like?
>

      Yes, tried that last night, and you were right, the bright spots
disappeared, but the diamonds looked more like Blue Topaz than
diamonds, but REALLY GOOD Blue Topaz!! (Because of my blue sky_sphere)

   (Note to self: must remember this!)




> Thanks for the heads-up on gemcad - sounds useful.  Very useful in
fact!

   My pleasure, "Anything to help anyone" would be my motto of choice.


   So, what do you reckon to the attached now?

   With this image, I stayed with IOR 2.41 in the end.


      ~Steve~


>
>

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Attachments:
Download 'h-d.jpg' (187 KB)

Preview of image 'h-d.jpg'

Now that's looking pretty good!  I'm going to have to try some gemstones
out myself...

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"Andrew" <ast### [at] hotmailcom> wrote in message
news:3e74727b@news.povray.org...

> Now that's looking pretty good!  I'm going to have to try some
gemstones
> out myself...

    Thanks! I'm not too happy with those blotches next to the sharp
edges (at the bottom), of the shank though. I'm not sure if it's a
sPatch thing or a texture thing at the moment...

   I'm going to try a ring with either eight or ten diamonds next,
surrounding an oval sapphire, or perhaps an emerald. I'll see if I can
put it in a pseudo velvet-lined ringbox too. That should be fun!  ;)

 Yes, give it a go, there's a sort of nice feeling being able to
produce a diamond that's FREE!

     (...and you can make it as big as you want!)    :)

      ~Steve~

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