As you know, the better animators are capable of drawing shapes (or, in the case of characters, shapes arranged into a design) over and over again, keeping the forms consistent and rendered in precise perspective.
They can, for example, draw a character whose head is comprised of five circles, eyes and facial features, and change all of these elements in myriad ways and still have them conform to rules of proportion and perspective.
My major difficulty at this point lies in defining shapes mentally and then rendering them accurately; in both my head and on my paper, the shapes are ill-defined and inaccurate, not to mention the state of the addition construction that I attempt to apply to them.
What exercises have these top animators done to be able to keep all of their forms so perfectly consistent and create such an amazing illusion of "real" mass that their drawings differ very little (in terms of accuracy and conveyance of depth and volume) from 3D renderings? What can I do to improve in this regard?
Thank you very much.