i was wondering if anyone had any suggestions on a 3D game engine that is free to use for non-commercial use. must be usable with either C# XNA or with C++ OpenGL. preferably can load a commonly used model type that has many free available models online(meaning: .md2 files fit the description also .obj as well, they are commonly available online). also can load textures from common picture file types or be able to use OpenGL/XNA textures. i prefer an OpenGL C++ engine. i am aware of Quake but i don't know how to set it up to use so a reference on how to set it up and tutorials on how to use are a must. that's it thanks.

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I hear Unity3D is pretty good, but I haven't personally used it myself- not sure if it meets your standards.

I'm sure a quick google can set you up in Quake fairly fast though.