Java/JavaFX/Kotlin Game Library (Engine)
A modern, cross-platform Quake game engine based on FitzQuake.
3D Engine c++
Odamex is a free, cross-platform, modern client-server Doom engine
A cross-platform port of Hexen II game.
GLScene Engine for Delphi & C++Builder VCL Windows 32/64
0 A.D. is a free, open-source, cross-platform real-time strategy game.
Zoomable user interface (ZUI) with file manager, file viewers and more
Game engine supporting many 3D/2D formats and graphic effects
X3D is the open-standard format for 3D graphics scenes on the Web.
A free 3d game for PC that does not limit the player. Fight,Build,Gain
C++ lightweight cross-platform game engine
functions for 2D/3D graphics + realistic driving simulation
Pycraft is an open-source, OpenGL based game made in Python
Vivid3D is an open-source 3D engine with powerful 2D UI.
SpaceStations, StarShip Division.
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Cinema Enters Game Console
DOOM / Heretic / Hexen source port with enhanced graphics and UI
ZED OS the clone of Windows XP
Modern 3D engine and IDE written using C# and C++.