On 2017-08-13 11:39 AM (-4), Stephen wrote:
> Looking at the site below. It looks to me that a 2D test will not
> represent a 3D object very well as for the pavilion, the Break Facets
> are rotated and not in the same plane as the adjacent Pavilion Mains.
> Actually I get the feeling that you might need to do two or three
> images. One for the Crown Mains with the Pavilion Mains and one with the
> Crown Break Facets with the Pavilion Break Facets.
> I assume that three angles are used in an emerald cut as opposed to two
> for a  brilliant cut?
>
> I've got a gut feeling that you need to do them separately.

The emerald cut is quite different from the round brilliant.  There are 
three crown facet levels, three pavilion facet levels, and no break 
facets.  A 2-D representation is quite adequate for the middle part of 
this cut.

> https://www.gemsociety.org/article/lapidary-fundamentals-gemstone-faceting/

The Web is replete with many different gem cuts and materials, but seems 
to have the particulars for only one cut and only one material.  The 
particulars on this page are for the round brilliant cut, and the stated 
angles indicate that the material they have in mind is diamond: exactly 
the information that is ubiquitous all over the Web, and therefore 
exactly *not* what I'm looking for.  (Whoever said diamonds are rare 
either hasn't done a Google search or works for De Beers' marketing 
department.)

Where it says that the procedures are the same for any material, they 
are referring to the technique, not the actual numbers that you plug 
into the machine.  And the technique is what I'm least interested in 
(for now), because I'm trying to simulate a gemstone, not cut one. 
(Hmmm, I see you point.  This probably isn't off-topic after all.)

Sorry.

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