Probably most readers do not play with the multiple ray-tracing option offered in DiamCalc©. A lot of fun and education can be derived there. The article ‘Fractioning of Color by a Gem’, published in PriceScope this week is just one of many interesting studies using it.

I am using DiamCalc 2.3.0; there may be more recent ones. In this article I use Brilliant, which is default, from Cut/StandardCuts, then proceed with the following choices:

On the MenuBar hit Options / Model Type / Ray Trace / Multiple Rays from Eye.

You will see a side view wire frame illustration of the round brilliant with paths of multiple rays.

Look at bottom row of icons: at left end is Angle°, showing 5°.

To the right of this are three pairs of rotation controls; the pair at left tips the gem left or right.

Hit the right member of this pair 8 times, this will tip the gem 40° anticlockwise.

Then change Angle to 1° and hit the left member once to back up to 39°.

Now hit the right member again to duplicate the pictures illustrated here.

To change things, go to Options/Advanced/RaytracingOptions.

The examples of the article were made with the following default settings:

Color: Red, Green, Blue (they will mix properly to give white)

Ray width: 0.02 mm

Reflections: 5 (this is maximum number of reflections shown)

Minimal Intensity %: 50 (rays less than 50% intensity will not be shown)

When you change anything, hit Apply for it to happen.

Leave this menu on and watch the effects as you change things ...

LIGHT SOURCE COLORS

Notice that many combinations of 3 or more colors can be mixed to produce white (the software chooses the appropriate proportions). It is interesting to see how these components separate/combine as you tilt the gem.

Seemingly incorrect separations/combinations can be explained if you reduce the Minimal Intensity that the illustration shows, but this can show so many rays as to be confusing.

SURFACE REFLECTION – an interesting illustration

This software can demonstrate surface reflection according to Fresnel’s law:

1. tip the gem to about 45°,
    
2. select 1 Reflection and any single light color, such as Red;
    
3. for Minimal Intensity 20% or greater no surface reflection shows;
    
4. at Minimal Iintensity 15% surface reflection appears.
   - this means that surface reflection is between 15 and 20% ...
    
5. type-in 17 and 18% and note that it shows at 17 but not at 18%
   - this means that surface reflection is between 17 and 18% ...
    
6. continuing, you will find that for Red light only it is between 17.7 and 17.8%;
    
7. similarly, for Green light only it is between 18.0 and 18.1%;
    
8. similarly, for Blue light only it is between 18.3 and 18.4%.

This is not important to the typical usage of DiamCalc but shows how powerful it can be as a teaching/learning tool.

B.L.Harding 2006 Dec 10