BOG FAQ Quick Jump

About BOG
How much does BOG cost?
Where do I get technical support?
What's new in version 1.2?

BOG Concepts
What is the difference between Old, Start, and End Angles?
What is tangent ratio scaling?

Running the Program
Do I need GemCAD to run BOG?
Which files does BOG create and use?
How to I get rid of the pop-up Tool Tips?

 

Running the Program

How much does BOG cost?

BOG is free. Although it represents a substantial investment of time and effort, at the end of the day, I wrote the program for myself. I have benefitted enormously from the freely-offered help of others in the faceting community (see here, for example), and BOG is an opportunity to give something back. You may also distribute the program non-commercially, although it makes more sense to direct potential users to http://www.boghome.com for the most up-to-date software and documentation.

Where do I get technical support?

I subscribe to the major faceting lists and try to read them daily. While you can send questions to me directly at tom@boghome.com, I would encourage you to use one of these public forums. Not only can the questions and answers benefit others, but also, there are many gem designers, optimizers, and cutters out there that are far more experienced than I.

Note that in the spirit of sharing information, I may (anonymously) include your question in this FAQ. Also please recognize that I will do my best to answer questions promptly, but I do have a real life (real job, real wife, real kids) as well.

What's in version 1.2?

Plenty! See this document for an updated list of new features. I think the Raytrace Overview is the most useful...check it out in the Merit Function Mapper tutorial.

BOG Concepts

What is the difference between Old, Start, and End Angles?

BOG uses three types of angles in the optimization process. The Old angles are the pavillion and crown angles extracted from the original GemCAD file. By default, BOG assumes these to be the Start (or initial) angles in the optimization, although this need not be the case. For example, if the user wants to transpose a gem design from quartz to CZ, it would make little sense for BOG to start with the quartz angles. In this instance, the user can override the default Start angles with more sensible values. The End angles are the outcome of the optimization process. Typically, the user will run GemCAD to tangent ratio the Old angles to the End angles. A description of this process appears here.

What is tangent ratio scaling?

Gem designers use a process called tangent ratio scaling to change the shape of a gem for optimal performance. This involves scaling all the pavillion or crown angles by a certain factor (the tan ratio), which changes the depth of the stone without altering its plan view - that is its facet outlines when viewed from above. For example, the gem at right is shown with three possible crowns. These gems will have different depths and optical performance, but the same plan view.

Tan ratio scaling is at the heart of BOG, and if you are unfamiliar with the process, you really should do a little reading. For example, Bob Keller has an excellent article on the subject at http://www.rockhounds.com.

 

Running the Program

Do I need GemCAD?

You do not need to understand or have GemCAD in order to benefit from BOG, although it can be useful for applying the results (see here). GemCAD is an excellent Computer Aided Design program to generate gemstone designs. You can download a demo at http://www.gemcad.com

I wrote BOG to complement GemCAD and GemRay, the companion program which calculates the trajectories of light rays through a stone. In simplest terms, I use GemCAD to design stones and BOG to optimize and cut existing designs.

You will, however, need the GemRay program (version 1.43 or later), which is available for free download at Robert Strickland's GemCAD site: http://www.gemcad.com

Version 1.2 of BOG can use either GemRay or GemRayX (or both!). GemRayX offers a number of additional features, including head shadow calculations and a measure of dispersion brightness. It, too, is available for free download at http://www.gemcad.com

Which files does BOG create and use?

BOG creates a number of files to store temporary results, images, etc. These are all located in the subdirectory BOGWork, located in the directory where you placed the BOG program itself. The program routinely cleans up after itself, so you shouldn't have a problem with a build-up of files in the BOGWork folder. Note that this subdirectory also contains the BOG Preferences, a copy of the GemRay.exe (and / or GemRayX) program and a file which restores BOG parameters (thereby allowing the user to continue where (s)he left off). You should probably avoid placing other files in the BOGWork subdirectory.

BOG will also create a number of files at the user's request. This includes sets of Optimization Targets, snapshots of raytraces, and Merit Function Maps for later study.

How do I get rid of the pop-up Tool Tips?

ToolTips are small windows that pop up with a hint when you pause the cursor over a control. Although these can be helpful for beginners, they will sooner or later drive you crazy. You can disable ToolTips in the Preferences window (About BOG:Customize BOG). Just un-check the tool tip option.

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Documentation maintained by Tom Herbst. Last modified 16-Aug-2005