aka ogre v2 - scene-oriented, flexible 3D C++ engine
FlightGear Flight Simulator: free open-source multiplatform flight sim
Open Source Solid Modeling CAD
LDraw™ editor for LEGO® style digital building instructions.
3D Without Boundaries
Python 3D renderer with wireless display support
Realtime raytracer using SIMD on ARM, MIPS, PPC and x86
rayshade and POV for Mathematica Export + view
For building cross-platform 3D geospatial apps in Java
Cross Platform Professional Procedural Terrain Generation & Texturing
Growth-grammar related Interactive Modelling Platform
Vivid is a modern C++ 3D engine using OpenGL4+
A shader-based software renderer written from scratch in C89
PyMOL is an OpenGL based molecular visualization system
3D Software Renderer in 700 Lines
Pear3DEngine is a modern and modular 3D development framework