No shape teaches light and shadow quite like the sphere. Highlights, halftones, core shadows, terminators, reflected light, and cast shadows all appear naturally, making it one of the most important value studies here.

The terminator is the boundary where the surface turns away from the light and the core shadow forms as a soft band wrapping the form. On a sphere that boundary curves in every direction at once.

Master it and you’ve unlocked every rounded form that follows, from a pupil, to a pearl, to a cheek, to a planet. They’re all the same problem at a different scales.

Change the color, material, or roughness, then reposition your lights and camera to supercharge the study.

The sphere teaches in curves. The Cylinder Shading Reference adds another side to the story.