GPL software which renders realistic skies in real time
Desktop/Android/HTML5/iOS Java game development framework
Cross-Platform C++ 2D/3D game engine
Console-based GLSL Sandbox for 2D/3D shaders shaders
3D Procedural Game Engine Using OpenGL
Software version control visualization
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
A toy physically based GPU path tracer (C++/OpenGL/GLSL)
Simple and light-weight 3D game engine
Parabator 2 - Free 3d board game
3D Without Boundaries
Surface Explorer 3D plots mathematical surfaces in 3D.
3D Engine c++
GemRB is a portable open-source implementation of the Infinity Engine
GLScene Engine for Delphi & C++Builder VCL Windows 32/64
Hardcore 3D space shooter with spaceship upgrade possibilities.