Army’s powerful open source solid modeling system undergoes modernization

By Kaylan Hutchison, DEVCOM DAC Strategic CommunicationsSeptember 21, 2021

BRL-CAD shotline analysis and advanced rendering visualization. (Photo Credit: DEVCOM DAC) VIEW ORIGINAL

Aberdeen Proving Ground, Md. — An integral part of preparing and protecting Soldiers is analyzing Soldier equipment, weapons and vehicles. Vulnerability and Lethality, or V/L, modeling helps provide a detailed picture of how potential scenarios and interactions of those components impact mission success.

That’s why the Army developed BRL-CAD, the first computer model to tackle the need to conceptualize military vehicles. Initiated more than 35 years ago at the U.S. Army’s Ballistic Research Laboratory, BRL-CAD is the primary tri-service cross-platform solid modeling Computer-Aided Design system used by the military to support analyses of military assets and their environments. The U.S. Army Combat Capabilities Development Command, or DEVCOM, Data & Analysis Center, known as DAC, maintains BRL-CAD software functionality for the Army. DAC’s Warfighter and Futures Integration Division provides enhancements, manages new releases and develops custom software to accelerate analysis.

BRL-CAD’s source code repository, with more than one million lines of code, is the oldest known continuously developed open source repository in the world. BRL-CAD enables more than terrain, vehicle, weapon and human modeling — it can now model a range of items from household appliances to NASA tools, securing its place in industry and in history as a fundamental benefit to a variety of engineering analysis work.

This past year, DAC has been giving BRL-CAD something of a face-lift. Clifford Yapp, DAC’s BRL-CAD model manager, is laying the groundwork to revamp BRL-CAD’s user interface, usability and overall functionality of the software.

“That groundwork is fundamental to taking BRL-CAD to the next generation in terms of how it is integrated and used,” BRL-CAD Software Developer C. Sean Morrison said.

“The industry has learned a lot of lessons that we want to apply to our core features,” Yapp said. “Developers are evolving the codebase to realize a modern interface that meets modern user expectations, making the core capabilities discoverable, explorable and useable to a new generation of users.”

More recently, DAC collaborated with the open source community to successfully migrate BRL-CAD’s project hosting and source code repository from the SourceForge hosting platform to GitHub, the largest collaboration platform for open source projects. DAC also made significant changes to their source repository for improved usability, traceability and collaborative impact.

“That was quite a substantial effort. Migrating BRL-CAD to GitHub isn’t just important for the vitality of the code — it’s the basis for our verification and validation. It helps us understand and assert that something has analytic value,” Morrison said.

Through this migration, the team has made preserving BRL-CAD’s history a priority. “Preserving our entire history is extremely important for DAC because that’s our institutional memory,” Yapp said. “That’s how I can look at a codebase that began its life around the same time I did, and still have some understanding of why the code is the way it is today. Version control history lets us maintain the code, access it and reference it, allowing us to be far more efficient while working to improve the program.”

BRL-CAD’s extensive history began in 1979, when senior research scientist Mike Muuss produced the initial architecture. In 1987, the first documented BRL-CAD software release was completed, and 1998, Morrison started a grassroots movement to expand awareness of the code and collaborate with others by converting BRL-CAD into a free open source software system. In 2004, BRL-CAD became the first U.S. Army code still in active development to become open source.

BRL-CAD Source Code Repository Hierarchy Visualization
Gource graph visualization of the BRL-CAD source tree circa June 2021, illustrating the complexity and activity achieved by 35+ years of development effort. (Photo Credit: Gource) VIEW ORIGINAL

As open source, BRL-CAD harnesses the power of distributed peer review and expands international visibility to unprecedented levels, ushering in contributions from around the world to significantly reduce maintenance, licensing and acquisition efforts.

“People thought it was a fantastic idea, and we immediately saw the benefit. In the first year, we had over 100,000 downloads and we started seeing contributions such as patches, bug fixes, portability improvements,” Morrison said. “It became this easy-to-see success story where we’re saving money, not draining our resources and developing faster.”

Yapp, too, acknowledges the benefits of BRL-CAD’s transition to open source in its transparency of process and strengthened foundation for progress: “No one else has to get it right again, we can just move forward. The force multiplier that humanity gets from being able to share that work collaboratively is so powerful, you can’t ignore it. It’s changing the world.”

BRL-CAD provides much of this support as the core geometry representation and high-performance ray tracing engine for DAC’s Advanced Joint Effectiveness Model, known as AJEM, which codifies the algorithms directly answering the tri-service community’s questions concerning V/L consequences of ballistic damage. BRL-CAD’s ray-tracing provides analytic guarantees, scalability, robustness and verified accuracy that can be perpetually extended as needed.

Solid Geometry Model of a Tank
Example of a BRL-CAD solid geometry model prepared for AJEM analysis. (Photo Credit: DEVCOM DAC) VIEW ORIGINAL
"I embraced BRL-CAD right away. I just fell in love with it," Morrison said. “From a developer’s perspective, we thrive at solving problems and love solving problems. There is a seemingly endless supply of interesting analysis challenges that lead to improvements in our understanding. It’s enjoyable work knowing we’re making a difference to help the warfighter.”

The DEVCOM Data & Analysis Center is an element of the U.S. Army Combat Capabilities Development Command. DEVCOM is a major subordinate command of the U.S. Army Futures Command. Visit the DEVCOM website at