True Reality (TR) is an open source LGPL Game and Simulation Engine written entirely in Standard C++ and OpenGL. It runs on all Windows platforms and GNU/Linux. OpenSceneGraph is used as its graphics engine, along with many other open source projects for support of various features.
https://codedocs.xyz/acidrainstudios/TrueReality/namespaces.html
Namespaces should have comments so they are picked up by Doxygen