dirty glass
A physically dirty pane—grease, dust, scratches, condensation, roughness, refraction—makes obstruction itself the interface to what sits behind it.
surface
Images exist behind a pane that never behaves like clean UI glass.
disturbance
Gestures smear grease, clear condensation temporarily, catch scratches at grazing angles, or warm a local region enough to change the optical path.
recognition
The obstruction is not merely hiding the image; it determines which evidence can become visible and how it is interpreted.
system
Multi-channel surface masks, refraction normals, roughness/scatter, SDF wipe tools, image families, and optional semantic relationships beneath the pane.