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Samuel Benge nous apporta ses lumieres en ce 2007/08/22 15:34:
> Bill Pragnell wrote:
>> Nice image, all the nicer for the colour bleeding!
>
> Thanks!
>
>> Surely the Miller indices define the crystal planes,
>
> Yes....
>
>> so you can use them
>> directly to define your intersection planes (i.e., no knowledge of angles
>> required)?
>
> No. I wish that were true, because it would make everything much easier.
> Now, it *might* be true for cubic crystal systems, but I have to check
> on that. For hexagonal systems that theory just doesn't hold.
>
> Look at the attached image. If we were talking just straight normals
> here, the numbers would be decimals or very large integers. Instead, we
> have angles represented by three small integers, ranging between -1 and
> 1 (they can be higher, I've seen them as high as 6).
>
> I don't understand how the Miller indices work, but I know it has to do
> with how molecules in the crystal are offset from one another. The
> Wikipedia article just confused me, as I have no formal training in
> higher mathematics.
>
> If you have a way to calculate the normals for single faces (not the
> angle between two faces), by all means, let me know! Otherwise, I'm off
> to try the answer via Google....
>
> Sam
>
> ------------------------------------------------------------------------
>
intersection{
plane{Miler_indice, 1}
.
.
.
material{...}
}
--
Alain
-------------------------------------------------
Rebellion against tyrants is obedience to God.
Benjamin Franklin
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Alain wrote:
> Samuel Benge nous apporta ses lumieres en ce 2007/08/22 15:34:
>> If you have a way to calculate the normals for single faces (not the
>> angle between two faces), by all means, let me know! Otherwise, I'm
>> off to try the answer via Google....
> intersection{
> plane{Miler_indice, 1}
> .
> .
> .
> material{...}
> }
Attached is an image demonstrating the result of that approach.
Here is the code:
intersection{
plane{z,1}
plane{-z,1}
plane{<0,-1,0>,3 }
plane{<1,-1,0>,3 }
plane{<1,0,0>,3 }
plane{<0,1,0>,3 }
plane{<-1,1,0>,3 }
plane{<-1,0,0>,3 }
pigment{rgb .5}
}
See the problem? These indices were supposed to make a hexagon, but
instead produced 90 and 45 degree angles. Am I missing something?
Sam
Post a reply to this message
Attachments:
Download 'wrong.jpg' (7 KB)
Preview of image 'wrong.jpg'
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Samuel Benge <stb### [at] THIShotmail com> wrote:
> Jim Charter wrote:
> > Samuel Benge wrote:
> >> The render itself is nothing amazing, but the possibilities
> >> represented by it are exciting!
> >>
> > Actually I thought the render itself *was* pretty amazing.
>
> Thanks Jim! I'm a little too self-critical sometimes, I guess :)
>
> Sam
I agree with Jim's comments, and add my own comments of "fantastic"
I've been wanting to do something like this, but had no clue how.
Nor even the knowledge to ask the question. I started searching with
the keywords: mineral, crystal and facet; but in over my head.
Thanks for sharing.
I'll be lirking around hoping to benefit from you hard work.
Leef_me
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"Samuel Benge" <stb### [at] THIShotmailcom> schreef in bericht
news:46cba80d@news.povray.org...
> Hi everyone,
>
> I discovered a way to accurately depict minerals with POV-Ray. I found a
> demo version of a program called KrystalShaper
> (http://www.jcrystal.com/products/krystalshaper/) which allows one to
> view various crystal morphologies for different minerals. The demo
> version does not allow you to save or export, but you can view the
> Miller indices (http://en.wikipedia.org/wiki/Miller_index) of a
> crystal's faces, and determine the angle between them.
>
> Using the angles acquired from the program, I made an intersection of
> planes to create the crystal. It would not be too difficult to randomize
> the result to make unique, natural-looking specimens.
>
> The render itself is nothing amazing, but the possibilities represented
> by it are exciting!
>
> Questions and comments, welcome as always!
>
> Sam
>
This render is really beautiful! I'll keep a copy in my private depository
of 'Beautiful images'.
Miller indices, yes... it's coming slowly back now. I used to have a
'Wulff's net' to analyse crystal shapes
http://euromin.w3sites.net/Nouveau_site/histoire/dates/pic_hist/wulff11.htm
and we used the Miller indices to place the normals of the faces on this 3D
projection...
Thomas
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Leef_me wrote:
> I agree with Jim's comments, and add my own comments of "fantastic"
Nothing like a little encouragement to spur me on :)
> I've been wanting to do something like this, but had no clue how.
> Nor even the knowledge to ask the question. I started searching with
> the keywords: mineral, crystal and facet; but in over my head.
Your post in p.general was what got me working in this direction. I've
wanted to render crystals with accuracy for quite some time, but always
ended up approximating the shapes, which never left me with a good feeling.
> Thanks for sharing.
> I'll be lirking around hoping to benefit from you hard work.
You're welcome! I hope to release file one in a series of mineral files
soon. Which minerals would you like to see realized? You mentioned
amethyst and fool's gold... what else?
Sam
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Thomas de Groot wrote:
> This render is really beautiful! I'll keep a copy in my private depository
> of 'Beautiful images'.
Thanks! I thought I overdid the glare.... it's approaching soap-opera
proportions :)
> Miller indices, yes... it's coming slowly back now. I used to have a
> 'Wulff's net' to analyse crystal shapes
> http://euromin.w3sites.net/Nouveau_site/histoire/dates/pic_hist/wulff11.htm
> and we used the Miller indices to place the normals of the faces on this 3D
> projection...
Thanks for confusing me with that! KrystalShaper has such a projection,
but I have no idea what it means or what it could be used for.
Sam
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"Samuel Benge" <stb### [at] THIShotmailcom> schreef in bericht
news:46ce1661$1@news.povray.org...
> Thomas de Groot wrote:
>> This render is really beautiful! I'll keep a copy in my private
>> depository of 'Beautiful images'.
>
> Thanks! I thought I overdid the glare.... it's approaching soap-opera
> proportions :)
>
>> Miller indices, yes... it's coming slowly back now. I used to have a
>> 'Wulff's net' to analyse crystal shapes
>> http://euromin.w3sites.net/Nouveau_site/histoire/dates/pic_hist/wulff11.htm
>> and we used the Miller indices to place the normals of the faces on this
>> 3D projection...
>
> Thanks for confusing me with that! KrystalShaper has such a projection,
> but I have no idea what it means or what it could be used for.
>
Yeah, well, this was just a piece of personal oral historical mumbling to be
sure :-)
If I may mumble on a little while longer:
I suppose that nowadays, Wulff's nets are not used anymore, at least not the
paper version, and computers should be ideal for that. What is confusing in
the image shown on the site I provided are the NSEW mentions. As far as I
remember, the vertical axis of the crystal is situated at the center and
perpendicular to the net; you put a piece of transparant paper on the net,
fixed at the center by a pin so that the paper can rotate around the
vertical axis; then you are supposed to be able to draw in the crystal face
projections using the Miller indices, but I don't exactly remember how this
was done (it was 40 years ago I last did that...). You do not get a crystal
of course, but projections in the shape of lines and circle segments as well
as the different symmetry axis indicated by conventional signs.
Mumble mumble.....
Thomas
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Samuel Benge <stb### [at] THIShotmailcom> wrote:
> Questions and comments, welcome as always!
>
> Sam
Great pic. Phear the Topaz bullet!
How did you do the background?
Post a reply to this message
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Samuel Benge wrote:
> Bill Pragnell wrote:
>> Nice image, all the nicer for the colour bleeding!
>
> Thanks!
>
>> Surely the Miller indices define the crystal planes,
>
> Yes....
>
>> so you can use them
>> directly to define your intersection planes (i.e., no knowledge of angles
>> required)?
>
> No. I wish that were true, because it would make everything much easier.
> Now, it *might* be true for cubic crystal systems, but I have to check
> on that. For hexagonal systems that theory just doesn't hold.
>
> Look at the attached image. If we were talking just straight normals
> here, the numbers would be decimals or very large integers. Instead, we
> have angles represented by three small integers, ranging between -1 and
> 1 (they can be higher, I've seen them as high as 6).
>
> I don't understand how the Miller indices work, but I know it has to do
> with how molecules in the crystal are offset from one another. The
> Wikipedia article just confused me, as I have no formal training in
> higher mathematics.
>
> If you have a way to calculate the normals for single faces (not the
> angle between two faces), by all means, let me know! Otherwise, I'm off
> to try the answer via Google....
>
> Sam
>
> ------------------------------------------------------------------------
>
From your example image:
intersection {
plane {
Miller.x * <1/sqrt (2), 0.5, 0> + Miller.y * <0, 1, 0>,
1 / sqrt (2)
}
...
}
But I don't know how the third number works, nor if it will hold
for Miller values other than +/-1...
Jerome
- --
+------------------------- Jerome M. BERGER ---------------------+
| mailto:jeb### [at] freefr | ICQ: 238062172 |
| http://jeberger.free.fr/ | Jabber: jeb### [at] jabberfr |
+---------------------------------+------------------------------+
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Version: GnuPG v1.4.7 (GNU/Linux)
iD8DBQFG1G/bd0kWM4JG3k8RAnHAAJ98eUQhyZiBRmvjvv7kAlonOx7OYgCeLuiB
8meA7fEarx61VdNz7i59QjY=
=ryqL
-----END PGP SIGNATURE-----
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Dear Samuel,
I saw your POVRAY Topaz image and I like it.
If you have a few of such images (plus *.pov files)
that you would allow me to bundle with
KrystalShaper I would give you the full version
of KrystalShaper for free.
KrystalShaper has already a simple POVRAY output
option, but I think I could improve the rendering by
learning from your files.
With best regards,
Steffen Weber
URL: http://www.jcrystal.com
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