Cross-Platform C++ 2D/3D game engine
Flax Engine, multi-platform 3D game engine
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Powerful, mature open-source cross-platform game engine for Python
3D Procedural Game Engine Using OpenGL
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
Doom-based AI research platform for reinforcement learning
3D Engine c++
Parabator 2 - Free 3d board game
GemRB is a portable open-source implementation of the Infinity Engine
A free 3D game engine to create games and realtimes scenes for Windows
An isometric arcade-style game of skill, puzzles and exploration
Simple 3d Top-Down Shooter & Free 3d Board Game
Odamex is a free, cross-platform, modern client-server Doom engine
GLScene Engine for Delphi & C++Builder VCL Windows 32/64
Cross-breeding a 3D FPS with a fantasy RPG in the world of Hexen
Maze creation, solving, exploration, and analysis
C++ lightweight cross-platform game engine