Of late, I have been playing with Sketchup, Google's 3D drawing thing. Not the perfect program, but a lot of fun for the money (free!).
One thing that has had me puzzled is the complexity of the roof in the barn - what goes where, how the load was spread - and what all those pieces do. Making a model in sketchup has actually helped me a lot with this. Not only have I looked properly at the photos, quite possibly for the first time, but it did allow me to work it out piece by piece.