An example of real-time engines finding their way into current architectural practice - and at the small domestic end even can be found at Lara Caldera Architects. Andrew Wallace is a final year UNSW student and worked on the UT3-ifying of THE EMBRACE. Looking at the presentation on the site you can see a variety of sketchy work, real-time vis and rendering.
Anyhow, check out what they converted across from Archicad to 3ds Max then to UT3 below. It is quite simple in terms of atmosphere and feels rather too CGlooking, but is still a great way to explore and experience the design - even though we are just seeing video here.
house_explore from adwallace on Vimeo.