"When white paper is used for the drawing, the paper theoretically represents the greatest--that is, the plane which is at right angles to the source of light. In all cases other than flat-front lighting, the form is rendered by the correct interpretation of the direction of the planes away from the right-angle planes, or the turning away of the form from the source of light." - Andrew Loomis
"The first and brightest planes are called the 'Light planes.' The next planes are the 'halftone planes,' and the third planes, which are unable to receive direct lighting because of their angle are called 'shadow planes.' Within the shadow planes may be those that re still receiving subdued, reflected light; these are called 'planes of reflection.' form cannot be rendered without a clear grasp of this principle. The planes are worked out in the simple order of: (1) light, (2) halftone, (3) shadow--which is the darkest and is at the point where the plane parallels the direction of light, and (4) reflected light. This is called 'simple lighting.' It is unquestionably the best for our purpose." - Andrew LoomisMy initial study above was decent but lacks repetition in doing more of them. For the moment I traced the outlines of the examples Loomis provided in his book (only a couple made up.) Filling in the form myself just to get a sense for how he starts and ends his lines. I see a lot of subtle dark to light line quality. He's pressing hard at first then possibly flicking away. I'm over complicating his mark making but I think a lot of that helps reinforce the illusion in areas where no contour edge is used to indicate form; if the mark has a darker to light line quality the form can sort of float in space and read as form. He has a lot of these floating marks in his examples.
I'll be supplementing this exercise in tomorrows Figure Drawing Workshop session. Focusing primarily on Loomis's "simple lighting" techniques, and posting my results.