Fire Performance Scope and other questions

[RockDoc]

Hi Sergey

I did look at the photos on the pages you linked to your reply.

On the photos with the girdle of the diamond..... on the photo the girdle appears to be not facetted - but in the Helium wire frame image it shows facetting.

Thanks for the reply...

Rockdoc

 

[Garry H (Cut Nut)]

The 3D model is built with flat planes with their position and orientation defined in spavce Roc.
So the girdle, which is curved, has been turned into an approximation model with many hundreds of flat planes.

 

[adamasgem]

Date: 6/23/2005 3:59:31 PM
Author: Garry H (Cut Nut)
The 3D model is built with flat planes with their position and orientation defined in spavce Roc.
So the girdle, which is curved, has been turned into an approximation model with many hundreds of flat planes.

Roc .. This is the way it generally has to be done for efficiency and is the correct technical approach, either for forward or reverse ray tracing.

However, if a diamond'' has a bruted (non faceted or polished) girdle, like many older stones, it effect on any resultant ray trace in which the ray happens to hit the girdle plane, may have significant effect, as there is more light loss, which reduces as the quality of the rounding and girdle finish improves.
A slight improvement in the apparent graded color grade may occur by faceting the girdle
If bruted girdle stone is heavily used (like in a master) you will get significant "drawing" of color due to contamination on the girdle by tweezer which can be a color grade or more, based on studies I have done, and having people boil their bruted girdle masters which had not seen acid since the day they were cut twenty years or more ago, SIGNIFICANT (one or more grades) changes in the color grade once they were clean.

If we are dealing with commercial Jeep wheels, then even any reverse or forward ray trace modeling modeling could be quite a bit off because of light loss.

Grease or oil on the pavilion of the stone SIGNIFICANTLY EFFECTS any realistic ray trace analysis, ie.. if the stone is dirty, modeling that doesn''t consider the pavilion (or crown) "oil" (like that from the skin) will NEVER match reality..