This is all good stuff.

I think we can count the quake projects as they do have 3D engines at the heart of them, and if someone wanted too they could use that code and extend it.

My main reason for asking is that the latest project I want to start will require a very advanced engine to do the things I want it too, I need to evaluate if any existing 3D engine can handle what I need to do , or if I should embark on that long road of writting my own, which will add years to the project.