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MAK Legion – Distributed Simulation at Unprecedented Scale

MAK Technologies is proud to announce the launch of MAK Legion — a next-generation Scalability and Interoperability Framework designed for real time distributed simulations at unprecedented scale. Legion combines the best concepts from established modeling and simulation protocols with cutting-edge online-gaming techniques to manage and deliver millions of high-fidelity entities.


street scene


Proven Scalability and Flexibility

On the US Army Synthetic Training Environment (STE) program, MAK has demonstrated Legion scenarios of up to 3.8 million pattern-of-life entities (using VR-Forces Sim Engines hosted on the AWS cloud). MAK has also successfully connected a wide variety of client applications, including VR-Forces, Bohemia’s VBS4, 4C’s Exonaut, the US Army’s OneSAF, Epic’s Unreal Engine, and the Unity game engine.


air traffic across the world



The Legion Design

MAK Legion takes a holistic, system-wide approach to scalability – solving the problems of generating, replicating, and filtering simulation entities, objects, and events within a large scale exercise:


Legion Monitor 1


The Legion SDK’s Data Store Library allows developers to build highly-parallelized simulation engines that take full advantage of modern multi-core CPUs – without having to worry about the complexity and performance impacts of locking and synchronization.

The SDK’s Network Library implements a communication protocol that connects multiple Sim Engines to achieve larger-scale scenarios; and enables client applications such as virtual simulators and first-person shooters to actively manage incoming traffic to maintain performance.

The Legion Server mirrors and maintains the full, authoritative state of the entire federation, and serves state and events to clients based on their specific interest criteria.



Data Driven Architecture

Together, these components act as a high-performance, spatially-organized, distributed simulation database – with each client’s Network Library continuously synchronizing the relevant subset of the Server’s database with the in-memory representation managed by the client’s Data Store Library.

MAK Legion supports a default built-in Object Model based on familiar semantics inherited from DIS, the RPR FOM, and SISO enumerations. It also provides a Code Generator that allows users to automatically extend the Legion SDK to support custom objects, events, and attributes.


Legion Includes:

  • Object-oriented, type-safe APIs for C++, C, Java, and C#
  • Code Generator and flexible component / extension system for user customization
  • Source code examples (talk, listen, give, take, and several extension examples)
  • Simple Clutter Client that can simulate and publish hundreds of thousands of entities on a laptop
  • Legion Monitor with bandwidth and CPU diagnostics, and 2D view of all entity locations
  • Windows and Linux support – for clients, Sim Engines, and Legion Server


Key optimizations that allow MAK Legion to achieve unprecedented scale: 

  • Data-oriented design – compact, contiguous, in-memory data representation for cache coherence
  • Data remains in a consistent format throughout the system – from sender’s Data Store, to the network, to the Server, and to the receiver’s Data Store – eliminating unnecessary marshalling and copying
  • Network Library is aware of internal Data Store layout – can access state data directly without per-attribute function calls
  • Double-buffered implementation enables multi-threaded applications without locking
  • Bulk send of “diffs” between local Data Store and Server for continuous low-latency synchronization of the database – updates thousands of entities with a single network send
  • Relevance filtering performed on server – clients receive only subscribed data
  • Stateful server can respond to late joiners without burdening the simulation application


Key capabilities:

  • Easy-to-use interest management with built-in whole-earth geographic filtering
  • Ownership transfer – allowing virtual simulators to take manual control of a CGF entity, and enabling transfer among Sim Engines to keep entities spatially organized as they move through the virtual world
  • Built-in support for the full breadth of HLA RPR FOM and DIS object models
  • Built-in optimized dead-reckoning
  • Deterministic results independent of tick order of entities, and temporal coherence of entities in formation - due to built-in concept of a simulation frame
  • Reliable TCP-based, client/server implementation
  • Cloud, WAN, or local deployment – run on virtual machines or containers, or install directly on a laptop



For a complete description of capabilities, please see the MAK Legion Capabilities document.

Why MAK?

The company that made it easy to simulate in DIS and HLA, now brings you the ability to scale into the millions with MAK Legion. Legion is built from the ground up by simulation experts for the simulation community. Consistent with MAK’s long-standing commitment to Open Standards, MAK has already begun the process of transitioning the Legion API (interface specification) to SISO as the basis for a future standard - MAK hosted a kick-off meeting for a SISO Legion Study Group at the virtual SIW conference in February 2021.

Do you want to scale up?

To evaluate the MAK Legion 1.0 software, to start integrating Legion with your own simulation engines or clients, or to learn about the progress we’ve already made towards scaling up our VR-Forces CGF using the Legion platform, please contact MAK sales at This email address is being protected from spambots. You need JavaScript enabled to view it..