Game engines are runtimes for interactive, real-time 3D — the technology behind games, but also virtual production, architectural visualisation, digital twins and simulation. This sub-hub covers the engines that matter: Unreal (the fidelity-and-scale leader), Unity (the broad, mobile-strong default) and Godot (the open-source challenger). It launches with Unreal — anchored on the shift that put it on this tree: 3D engines are becoming agent-driveable surfaces via the Model Context Protocol.
Each leaf follows the standard shape: what it is, how it works, what it's used for, pricing reality, decision guide, SA context, connections, resources. Unreal is the first — the others land as the band grows.
Epic's real-time 3D engine — AAA games, virtual production, archviz, digital twins. UE 5.x with Nanite, Lumen and MetaHuman. The reason it's here now: UE 5.8 ships an embedded MCP server, making the Editor an agent-driveable surface. Free to use with a royalty / seat model; demanding on hardware and skills.
The broad default — C#-based, mobile-strong, the largest asset ecosystem. The pragmatic choice for cross-platform and 2D/3D mobile games, AR/VR, and a huge indie base. The runtime-fee controversy and its walk-back are part of the honest picture.
The open-source engine — MIT-licensed, lightweight, no royalties or seat fees ever. Risen fast for indie and 2D, and the natural pick when ownership and a permissive licence matter most. The "own your stack" engine.
Real-time 3D used to sit apart from the rest of the stack. Three things pulled it onto this tree — and each connects to a branch that's already here.
Unreal 5.8's embedded MCP server means an AI agent can drive the editor — spawn actors, set lighting, build materials. The same agent-driveable-surface idea from the agents domain, reaching 3D. The supervisor-not-author pattern applies.
A live 3D mirror of a building or factory, fed by sensor data, is a real-time engine on top of an openBIM model and an IoT feed. Game engines are where the built environment and operational data become visible and explorable.
LED-volume film sets render their backgrounds live in Unreal. Real-time 3D is now part of the generative-media pipeline, sitting alongside the voice, image and video work in the media domain.
Real-time 3D is a crossroads. These are the branches it pulls on most.