drawing with a pencil is easy. the more you draw the more fun it is. i am working with a 3d drawing program: vectorsworks which i am able to work with. i am not an expert but in general i know how the program works and what i should do and can do.
drawing with a pencil however is different, more fun, more intuitive, more open and more direct. with the keyboard and the mouse is different story, especially making 3d drawings. some years ago i was interested in making 3d scetches not with a pencil but with thin steel rods. the fisherman is an example of one of the results. the project for berlin is another. working with little steel rods and an experienced welder is almost like scetching with a pencil.
a 3d drawing is just like a normal pencil drawing: you add one line after another, not with a pencil but with a welding rod. the scetch however cannot be redone. it is impossible to copy in a 100% way. and because of the irregular character, it is impossible to reconstruct in a 3d drawing program.
my scetches for a 3d table with 4 chairs, built from 3mm steelrods, have to be redone and re-thought in order to allow a 3d computer drawing. the drawing is necessary for future strength analysis, logistics and more in general for consistent 3d presentations. more or less the original scetches are rather loose. the 3d computer drawing is rather stiff. that is a pity but i have not found another way yet.