So i found this site Reactor 3D - XNA Game Engine
in in there reads:
With Reactor 3D, you have the satisfaction in knowing that your game idea can become a reality. Reactor 3D was written with the "code once, compile twice" theory that has made Microsoft© XNA Framework so popular.
Reactor 3D Engine's core is a powerful C# XNA library which takes away the requirement to know 3d geometry and brings you, the developer, straight into game code. A World Editor allows your builders to design a game world and see it as it would be in the game. A Shader Editor allows your graphics programmers the flexability to debug and script high quality shaders for Reactor 3D.
Above all, it grants you the power to fuel any game project on Windows or XBox 360.
I don't know much about programming but i also found this video: [ame=http://www.youtube.com/watch?v=6PBoEaY8u7E]YouTube - Xna World Editor[/ame] and i though you expert World Builders/ Programmers should take a look at it.
The programs beta can be downloaded from:
http://reactor3d.ath.cx:8000/svn/Reactor
Account: Anonymous
Password: Anonymous
What do you think?