C# graphics library used for 3D modeling, built with OpenGL/OpenTK
Control to create diagrams in winform applications in C# (.NET)
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
OpenFlight (.flt) importer for the Unity game engine.
A free and open source screenshot tool optimized for productivity
3D .NET engine for Windows, Linux, Mac
Investigo - DX9 Performance and Debugging Toolkit
Multi-Language Wrapper Collection for the Irrlicht Engine
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor