These are the exercises I worked on with a student today. I am terribly pleased with myself because I achieved my goal of 1. getting the student to draw something in his sketchbook (draw something period) 2. having him loose himself a bit in the process. 3. think about creating the illusion of form on a page and hopefully, 4. having him see the relationship between these exercises and his favorite drawings.
The spheres proved frustrating so I chose the simpler cube with only three values and no modulation between them. Brilliant me!