occlusion is information
Several forms can never be seen at the same time; moving one aperture into clarity necessarily hides another until a structure must be inferred from partial views.
surface
A scene appears to be inconveniently blocked.
disturbance
Moving shutters, SDF apertures, depth layers, or fog can reveal one relationship only by concealing another.
recognition
Absence is also evidence. The visitor can understand a structure that was never available as one simultaneous image.
system
Depth-sorted layers, SDF masks, constrained reveal geometry, temporal memory, and optional related image families.