Three-dimensional form comes from one idea: wherever light strikes an object, that area reads as a
highlight or bright zone. The surface that turns away from the lamp falls into
shadow. You do not need fancy tools to see this. Hold any object near a window or lamp and watch one side glow while the other side sinks darker. Your pencil job is to copy that split honestly. Even a silly alien spaceship in a top hat looks solid when the hat brim catches light on one edge and the hull drops into shade on the far side.
⚡ DID YOU KNOW?
Animators often place the key light above and to one side so faces and props read clearly. That same angle works great for your first shading studies.