POV-Ray : Newsgroups : povray.binaries.images : topaz (84k jpg) : Re: topaz (84k jpg) Server Time
2 Aug 2024 16:25:40 EDT (-0400)
  Re: topaz (84k jpg)  
From: "Jérôme M. Berger"
Date: 28 Aug 2007 14:56:22
Message: <46d46fd6$1@news.povray.org>
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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 ---------------------+
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