Am looking for Concave Faceting Design Tips

[FlashGP]

I was thinking .... we have computer programmes for predicting brightness in flat facet gemstones, but I doubt there are programmes that do this for concave cuts.

At present it seems a case of try it and see.

Does anyone know of a model or theory for predicting how light behaves when it hits a concave facet?

Or how to set the angle to look good?

regards
Gordon.

[Buch Metter]

Yeah, that's a good question Flash.  My thinking is that the angle would not differ from a straight facet because all one is doing is bending the facet angle and so bending the light return.  ? Yes?

[Rej]

No promises, but this is one area I'd really like to explore in my upcoming app.

Given how hard it already is to "guess" how light behaves in a flat-facet design without doing some tedious paper math or running through a raytracer, you can imagine how much harder it is when the light gets thrown around in an arc.

But that's why we invented computers! 

[Orange Pirate]

No promises, but this is one area I'd really like to explore in my upcoming app.

Any time frame yet on the app? It looks good from the screen shots and the testing seems to be giving fantastic feed back.

[Rej]

Any time frame yet on the app? It looks good from the screen shots and the testing seems to be giving fantastic feed back.

Sigh, it was supposed to be out already, but I'm still putting together a website, documentation and tutorials.

The first 90% of development always goes to plan, it's that last 90% that takes forever 

[FlashGP]

My current theory is that the concave facet would behave like a flat plane in the direction running from the girdle to cutlet so the critical angle is still relevant here and and a curved plane in the direction perpendicular to the flat part of the plane.

Hence light in a plane parrallel to the C axis of the stone would strike the facet at an angle similar to the angle at which the facet is cut after allowing for bending as the light passes through the crown.

But as it strikes the facet it is fanned out by the curvature, spreading it around the inside of the stone.  What happens next depends on which facet it strikes, flst or concave.

Any thoughts?

Regards
Flash

[Ghost]

The library page on Ultratech's web site has a design and some articles on concave faceting that may help.
Regards, ghost.

[FlashGP]

Thanks Ghost

The couple of diagrams in the articke help.

Regards
Flash