# BRL-CAD Tutorial Series: Volume II - Introduction to MGED

Army Research Laboratory ARL-SR-102
April 2001

Approved for public release; distribution is unlimited

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## Preface

Since 1979, the U.S. Army Research Laboratory (formerly the Ballistic Research Laboratory) has been developing the BRL-CAD constructive solid geometry (CSG) modeling package for a wide range of military and industrial applications. The strength of the package lies in its ability to build realistic models of complex objects from a relatively small set of "primitive shapes" by employing the basic Boolean operations of union, subtraction, and intersection and by assigning real-world material attributes.

The package comprises a large collection of tools, utilities, and libraries including an interactive geometry editor, ray-tracing and generic framebuffer libraries, a network-distributed image-processing and signal-processing capability, and an embedded scripting language.

Although BRL-CAD has continued to mature in performance and utility, developers have strived to keep the package approachable and easy to use, as evidenced by the package's dual command formats, its newly renovated graphical user interface (GUI), and its customization potential through user scripting.

In addition, a multivolume tutorial series is being developed to assist users in a variety of BRL-CAD areas and applications. The "Introduction to MGED," which is the second volume in the series, is intended to provide new users with a basic understanding of the Multi-Device Geometry Editor (MGED), which is the heart of the BRL-CAD package. Other volumes focus on installation procedures, advanced features, and programming.

## Acknowledgments

The authors would like to thank Paul Tanenbaum, TraNese Christy, Sean Morrison, and the other members of the Advanced Computer Systems Team who reviewed this document in a timely manner and made many helpful suggestions to improve its accuracy and presentation.

In addition, the authors would like to acknowledge team member Mike Muuss, who passed away while this volume was in preparation. Mike was the original architect of the BRL-CAD package and guided its development for 20 years until his death on 20 November 2000. He embodied a unique blend of unparalleled intellect, unquenchable curiosity, and unending energy to advance the capabilities of everything and everyone he touched. A natural-born troubleshooter, Mike approached every job, big or small, with a passion for excellence and a child-like enthusiasm, which helped drive BRL-CAD far beyond expectations.

Although he never got a chance to review this document, much of this work is a result of his vision and attention to detail. Therefore, the BRL-CAD Tutorial Series is dedicated to his memory. His sharp mind, his warm spirit, and his loyal friendship will be greatly missed.

## Creating Primitive Shapes

## Learning the Viewing Options

## Using the Insert Command to Size and Place Shapes

## Assigning Material Properties and Raytracing

## Lesson 5: Learning About Boolean Expressions

## Creating a Goblet

## Assigning Material Properties to Your Goblet

## Assigning More Material Properties to Your Goblet

## Creating a Globe in a Display Box

In previous lessons, you combined various shapes into new objects. These new objects have been created using solid building blocks, much like those used in a wooden toy truck. However, in real life, most of the objects that you will design will consist of an outside shell and various inside parts.

## Creating a Mug

## Refining the Mug

## Creating the Mug Through the GUI

## Placing Shapes in 3-D Space

## Gaining More Practice Placing Shapes in Space

## Creating a Toy Truck

## Learning Modeling Techniques and Structures

## MGED Commands

Appendix