Shadow terminator

Plural: shadow terminators

Shadow terminator definition

The boundary line on a form where light transitions into shadow, separating the light family from the shadow family.
The specific zone on an object where direct light no longer reaches, marking the beginning of form shadow.
In rendering and painting, the edge that defines the turning point of a surface away from the light source.

Examples

On a sphere lit from one side, the shadow terminator appears as a soft curved line dividing the illuminated side from the shaded side.

In portrait painting, the shadow terminator runs along the cheek and jaw, helping define the structure of the face.

Context

The shadow terminator is a fundamental concept in drawing and painting, especially when studying light and form. It does not represent a hard outline but a transition zone where the form turns away from the light. Its position depends on the direction of the light source and the orientation of the planes of the object. Understanding the shadow terminator helps artists correctly separate light family values from shadow family values and build convincing three dimensional form.

Core Principles

Derivation

From Latin terminator, meaning “one who sets boundaries,” combined with “shadow,” referring to the absence of direct light. The term describes the boundary where light ends and shadow begins.

The Lexicon by Alex Righetto