Fog increases realism and can be used to set a mood, even indoors.
Add fog outside to create hazy worlds, or add fog inside to create dark dungeons.
Fog has a color, a type, and a visibility range.
Fog limits the viewer's sight, reducing the amount of the world you have to build and the amount of the world that must be drawn.
These X3D scenes are adapted directly from the
original VRML 2.0 Sourcebook chapter examples.
Introduction to VRML97 SIGGRAPH98 course notes.