Design Nomenclature / Light & Optics
Cast shadow
Also called projected shadow, thrown shadow
The shape an occluder subtracts from another surface's illumination. Unlike a form shadow it has a projected outline governed by the geometry between blocker and receiver: it sharpens as the two approach contact and softens as they separate, regardless of the object's own shading.
Not to be confused with
- Form shadowThe region of an object turned away from the light — unlit because of its own orientation, not because anything blocks the source. Its boundary is the terminator, its edge softens in proportion to the source's angular size, and almost everything in it arrives as indirect light.
- Contact shadowThe tight dark shadow in the crevice where two surfaces meet, produced because almost none of the surrounding hemisphere is visible from that point. It is the cue the eye uses to decide whether an object rests on a surface or floats a little above it.