SimCore GT was the game engine and toolset I designed and worked on at Raydon.
At the time, most game engines could not support features unique to the simulation training industry: large terrain datasets, long-range visibility, replay capability, simulation industry data formats, etc.
We evaluated Unreal 2 and Unity, but besides the technical challenges involved in using either (i.e. adding our feature needs on top), neither Epic nor Unity could offer reasonable licensing terms for the Raydon business model since we were one of the few companies approaching them from the simulation industry with a non-games business model.
Of course, times are different now, but there were all kinds of hurdles to cross to get these engines at parity with our needs.
SimCore GT had a game-object component architecture and used a mix of about 40 open source and commercial 3rd party components to implement technology subsystems. For example, our rendering engine was Ogre, PhysX for physics and collision detection, AI.implant for pathfinding and agent behavior, and RakNet for our networking base.
We built a variety of tools for entity editing, scenario editing, Maya exporting, and so on. One of the coolest things we probably did was the equivalent of the modern Unreal Blueprint system, where our software engineers implemented nodes our content creators could use as building blocks to design complex scenarios.