In my experience, the dimensions in 3D documents --like the 3D document functionality itself-- is a real disappointment. It's a shame: With a little vision and a more serious execution, it could have been so good. But because this is ArchiCAD nothing will change in the tool for eons until it is replaced by something marginally better but which you have to pay for in an "upgrade".

If you change the shape/size of a dimensioned element, the dimension may or may not update. You can't count on it. But worse is that if you change the view angle of the document, the dimensions go to complete crap. They just go haywire.

But the biggest disappointment is that the 3D doc menu relies on the old, nasty, slow internal 3D engine and cannot display materials/textures.

/sigh