The Irrlicht Engine is an open source high performance realtime 3D engine written and usable in C++ and also available for .NET languages. It is completely cross-platform, using D3D, OpenGL and its own software renderer, and has all of the state-of-the-art features which can be found in commercial 3d engines.
This is a easy but full tutorial on how to make a character to move.
These are the basisc of the Irrlicht Engine.
This tutorial shows you how to create an user interface