aka ogre v2 - scene-oriented, flexible 3D C++ engine
Real-time physically based rendering engine for Android, iOS, and more
Viewer and exporter for Unreal Engine 1-4 assets
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
Gimpel3D - 2D/3D Stereo Conversion Editor
A C++ library to easily create GUI-editable objects