Shading: light on form
Light falling on a rounded form produces a predictable sequence of tones. Once you know the sequence on a sphere, you can apply it to faces, fruit, drapery and everything else.
Step by step
- Decide where the light comes from and keep it consistent. Draw a small arrow in the margin if it helps.
- Find the terminator — the line where the form turns away from the light. Separate light side from shadow side along it.
- On the light side: highlight (the brightest spot, a reflection of the light source), then light and half-tone as the surface turns.
- On the shadow side: the core shadow sits just past the terminator and is the darkest part of the form shadow. Further round, reflected light from nearby surfaces lightens it slightly — but it stays darker than any value on the light side.
- Add the cast shadow on the ground. It is darkest and sharpest where the object touches the surface (the occlusion or contact shadow) and softens as it moves away.
- Choose a shading method — hatching, cross-hatching, or smooth blending — and follow the form with your strokes.
Common mistakes
- Making reflected light so bright it competes with the light side.
- Forgetting the contact shadow, so objects look like they float.
- Shading in random directions that fight the form.
Practice exercise
Render a sphere, a cube and a cylinder under one light source. Then shade an egg or an orange from life.