Value (how dark or light) and contrast (difference between two values)
Positive space (what your object is) and negative space (everything else)
Shading of 5 Basic Geometric Shapes, with light source in top left
- Cube - flat faces
- Sphere - circle when unshaded. shadows and highlights give it 3D illusion. roundd shadows.
- Cylinder - part flat, part rounded like sphere
- Cone - like a cylinder, but tapers to the top point
- Pyramid - none of the middle value. just lighter and darker.