If you're using the Civil or architectural add-ons for AutoCad, they're pretty much creating working 3D drawings as it is. Now, if you're using Viz to render your work from those packages, you're in for some growing pains. Several years back I taught myself to use 3D Studio Viz 3.0 before it was overrun.. umm, purchased by AutoDesk and to tell you the truth, I'd rather have to learn AutoCad all over again.. TWICE before I tried learning Viz again.
But, once you figure it out, it makes some suhweet pictures.
First thing they teach you at Viz school, never do flyby's or walk-thrus... I wish I had known that one before I did a 2 minute walk-thru that took 84 hours to process on a then top of the line computer.
Viz is a tough one, I gotta admit.. Really hard to justify the amount of hours it takes to make something pretty for the client to see.
Just my 2 cents...