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

Post a reply to this message

"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

Post a reply to this message

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

-----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   |
+---------------------------------+------------------------------+
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (GNU/Linux)

iD8DBQFG1G/bd0kWM4JG3k8RAnHAAJ98eUQhyZiBRmvjvv7kAlonOx7OYgCeLuiB
8meA7fEarx61VdNz7i59QjY=
=ryqL
-----END PGP SIGNATURE-----

Post a reply to this message

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

Post a reply to this message