I am looking for a game engine with multiplayer support that allows for players to place objects in the terrain. (eg. in TF2 one can place teleporters, etc...or in minecraft one can place blocks). I don't need the placeable objects to be interactive like in TF2, but I just need an engine that won't make me code this from scratch. I have decent knowledge of Python, PHP, HTML, C++ and C# (and a small knowledge of Lua scripting, although I have only been at it for a few months) so I should be able to handle most engines. So far I have looked at UDK and Cryengine, and wasn't thrilled with either.