@pastanaga - Honestly, it's the originality that amazes me. I don't know if there is a point where someone just becomes so familiar with the different folds that they can just imagine a sculpture and know how to make it, but it just seems impossible to me.
It's not like sculpting with stone or clay where it's just a matter of making the material look the way you want it to.
It's more like making a clock or something, in that you have to understand how all the pieces work together before you even start, or it won't work.
I have a hard enough time making origami by following instructions, let alone making up original creations.