Irrlicht Engine - A free open source 3d engine

Irrlicht Engine - A free open source 3d engine

"The Irrlicht Engine is a cross-platform high performance realtime 3D engine written in C++. It is a powerful high level API for creating complete 3D and 2D applications like games or scientific visualizations. It comes with an excellent documentation and integrates all the state-of-the-art features for visual representation like dynamic shadows, particle systems, character animation, indoor and outdoor technology, and collision detection. All this is accessible through a well designed C++ interface, which is extremely easy to use.

...
.NET language binding which makes the engine available to all .NET languages like C#, VisualBasic, and Delphi.NET. ..."

There are a number of pretty cool tutorials too. For example,
"1.HelloWorld
Shows how to set up the Visual Studio IDE for using the Irrlicht Engine and how to write a simple HelloWorld program with it. The tutorial will show how to use the basics of the VideoDriver, the GUIEnvironment and the SceneManager."

There is also a very cool .Net specific API documentation at API.Net