It is not possible to render a true parallel projection in the walkabout window. If you want the control over sizing that the walkabout window gives you, or you want to use radiosity, then you can cheat. Use the following steps:
Set your target to the middle of the wall you want the elevation of.
Set your camera to look straight & flat at that point, from about a kilometer away.
Make your lens length very long, to fit the elevation in the walkabout window.
If needed, create an arbitrary clipping plane, to "section" the building.
This will create a view that is all but parallel. As long as you are far enough away, you will not be able to see the converging lines of the perspective. If you need to get further away, use orbit and move further away, then set the lens again.
rev 06.5.01 :: For more information visit www.accustudio.com