Perspective of Shadows

We can simplify the perspective of cast shadows into three parts: light source, object, and surface.

Diagram showing light source, sphere, and surface

The shape of any cast shadow will be determined by the relationship of these three things.

Diagram illustrating the relationship of light source to length of cast shadow

A change to any one of these three things will alter the shape of the shadow. For example, changing the position of the light source changes the length of the cast shadow.

Diagram shows cast shadow length changes as light source is raised or lowered

The shape of the object also impacts the shape of the cast shadow.

Cast shadow changes shape based on shape of object casting it

Finally, any change to the surface will impact the shape of the cast shadow.

Illustration of shadow falling on hilly surface

The image carousel below illustrates how a cast shadow conforms to different surfaces. As the surface changes, so the cast shadow changes.

There are two main approaches to plotting cast shadows in perspective: Sunlight Theory and Local Light Theory (or "artificial light").

diagram comparing shadows created by sunlight and local light

Sunlight from the side is a unique case in which all light rays are parallel and there is no convergence of cast shadows to any vanishing point. This situation occurs only when the direction of light is exactly perpendicular to our line of sight.

Diagram of cast shadow from a cube, with sunlight coming from left

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