- illusory contour figures : radial line segments whose inward-pointing end produce the illusion of a circle or other figure. The apparent figure has the same color as the background, but appears brighter
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- impossible figure : a class of illusion in which an object which is physically unrealizable is apparently depicted.
- ambihelical Hexnut
- freemish Crate
- home plate
- impossible joinery
- impossible torus
- Klein bottle
- Necker cube
- Penrose stairway
- tribar
- tribox
- perception illusions
Kanizsa triangle : the eye perceives a white upright equilateral triangle where none is actually drawn.
