An artistic technique {linear perspective}| depicts scenes as they appear to human eyes.
picture plane
Imagine standing in front of a window looking onto a street or yard. Window is a vertical plane, parallel to line between your eyes. Straight lines of sight go from eye to scene points. See Figure 1.
Lines go through window at unique points. Artists paint scene-point color at the unique point in the picture plane. See Figure 2. Farther scene points have higher picture-plane points.
lines
In linear perspective, vertical lines stay vertical. See Figure 3. Scene points 1 and 2 make vertical line, and their picture-plane points make vertical line.
In linear perspective, horizontal lines stay horizontal. See Figure 4. Scene points 3 and 4 make horizontal line, and their picture-plane points make horizontal line.
The ground is plane and meets wall in horizontal line in scene and picture-plane. Ground meets sky in horizontal horizon line in scene and picture-plane.
horizon
Horizon height depends on eye height. Observer high above ground sees large ground amount and low horizon. Observer close to ground sees small ground amount and high horizon.
Observer attention typically moves along eye-level line.
line convergence
In linear perspective, non-vertical and non-right-left parallel lines converge and intersect at vanishing point. See Figure 5. Scene points 5/6 and 7/8 make two parallel lines, and their picture-plane points form two lines that converge toward a horizon point.
For parallel lines in horizontal plane, vanishing point is on horizon. For parallel lines in plane that rises as it goes farther from observer, vanishing point is above horizon. For parallel lines in plane that goes lower as it goes farther from observer, vanishing point is below horizon.
history
In Early Renaissance, Europeans studied al-Hazen's book [al-Haytham, 1010] about perspective and began to paint using linear perspective.
In linear perspective, parallel lines that are not vertical or horizontal intersect at vanishing point, so line ends converge {convergence line, painting} {orthogonal line, painting} {vanishing line, painting}.
Where horizon line goes through imaginary window indicates eye viewpoint {eye-level}. Observer attention typically moves along eye-level line. Viewpoint depends on ground amount compared to sky amount. Eye-level/horizon high in window or painting shows much ground. Eye is looking down on scene from high above ground. Eye-level/horizon low in window or painting shows little ground. Eye is looking up at scene from close to ground.
Objects have lowest point, through which line {ground line} can be horizontally parallel to window plane.
Horizontal ground plane, including treetops, buildings, or hills, and sky or wall bottom meet in a horizontal line {horizon, painting} in windows or paintings. Where horizon line goes through window indicates eye level.
Imagine standing in front of a vertical rectangular window {picture plane} {plane of picture} looking onto a street or yard. The picture plane is a vertical plane parallel to the line between the two eyes.
Straight lines {line of sight} {sightline} go from eye to scene points.
Eye is reference point {station point} in linear perspective.
In linear perspective, parallel lines that are not vertical or horizontal intersect at a point {vanishing point}|, so line ends converge {convergence line, perspective} {orthogonal line, perspective} {vanishing line, perspective}.
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Date Modified: 2022.0225