If you haven’t yet seen Joe Wintergreen’s stunning Half-Life map renders in Unreal Engine, check this out.
What you see here isn’t just an art project, but part of a unique map creation technique Joe experiments with. Using this method, a map is first built in Hammer to take advantage of the intuitive world geometry creation tools. Afterwards it is ported to Unreal Engine, which Joe tells us makes it easier to fine-tune in aesthetic details.
The program used to port Source maps to UE is called HammUEr, and was custom-created by coder Turfster for Joe’s method of map creation.
You can see the process in action in these videos: