Understanding light source direction and how objects cast shadows is fundamental to creating convincing form and space. Shadows reveal light direction and form shape. Core shadows (where light doesn't reach) differ from cast shadows (projected by the object). Light direction consistency throughout a composition prevents visual confusion and enhances three-dimensionality.
Draw from a single light source with simple objects: spheres, cylinders, cubes. Observe where shadows form and how they change with light angle.
Placing shadows randomly or inconsistently throughout the composition. All shadows must respect the same light source.
Your prerequisite work with light and shadow taught you the basic vocabulary: highlight, halftone, core shadow, reflected light, cast shadow. You know that these zones exist on a form. Directional light and shadow casting takes that knowledge and makes it predictive — given a light source at a specific position, you should be able to construct where every shadow falls before you even observe it. This is the leap from copying what you see to understanding why you see it.
Start with the simplest case: a single point light source illuminating a sphere on a table. The light travels in straight lines from the source to the object. Where those rays hit the sphere, you see the lit side — highlight, light halftone, dark halftone. Where the surface curves away far enough that light rays can no longer reach it, you find the core shadow, the darkest band on the object itself. The core shadow is not at the edge of the sphere but slightly before it, because at the very edge, light bouncing off the table and nearby surfaces creates a thin band of reflected light. This reflected light is subtle — always darker than the halftones on the lit side — but it is what makes a form look round rather than flat. If you understand chiaroscuro, you have already practiced these transitions; now the goal is to predict exactly where each zone falls based on the light's direction.
Cast shadows are the projected silhouettes that objects throw onto surrounding surfaces. To find a cast shadow's shape, imagine drawing straight lines from the light source past the edges of the object and continuing them until they hit the table or wall. Where those projected lines land defines the cast shadow's boundary. A light source that is close to the object produces a large, diverging cast shadow (because the rays fan out sharply). A light source that is far away produces a smaller, more parallel cast shadow. Cast shadows are darkest and sharpest at their base — where the object meets the surface — and become lighter and softer at their far edges, because ambient light fills in the distant portions. This gradient from sharp to soft within a single cast shadow is called the penumbra effect, and rendering it correctly is one of the strongest cues for believable space.
The critical discipline is consistency. Every object in your composition must obey the same light source. If your light comes from the upper left, all highlights face upper left, all core shadows wrap to the lower right, and all cast shadows fall to the lower right and slightly forward. The moment one object's shadow contradicts the others, the illusion of unified space collapses. When working from observation, check consistency by extending imaginary lines from each shadow back toward the light — they should all converge at the same source. When working from imagination, establish the light position first (mark it in the margin if needed), then construct each shadow systematically. This methodical approach is what separates convincing representational work from drawings that feel "off" without the viewer being able to articulate why.
Topics in reflective domains aren't scored by quiz answers. Read, reflect, and mark when you've thought it through.