Boundaries {contour, vision} have brightness differences and are the most-important visual perception. Contours belong to objects, not background.
curved axes
Curved surfaces have perpendicular curved long and short axes. In solid objects, short axis is object depth axis and indicates surface orientation. Curved surfaces have dark edge in middle, where light and dark sides meet.
completion
Mind extrapolates or interpolates contour segments to make object contours {completion, contour}.
When looking only at object-boundary part, even young children see complete figures. Children see completed outline, though they know it is not actually there.
crowding
If background contours surround figure, figure discrimination and recognition fail.
Two line segments can belong to same contour {relatability}.
Perception extends actual lines to make imaginary figure edges {subjective contour}|. Subjective contours affect depth perception.
1-Consciousness-Sense-Vision-Physiology
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Date Modified: 2022.0225