Visual Plane
every picture states the point it is correct from
Concept

Affine map — where it appears

2 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
elevationx 1.000y 1.000z 0.000cavalierx 1.000y 1.000z 1.000cabinetx 1.000y 1.000z 0.500isometricx 0.816y 0.816z 0.816dimetricx 0.943y 0.943z 0.471axis scales measured from the drawingall 5 preserve midpoints

Parallel projection is not primitive perspective

Isometric and oblique drawing are not what people used before they worked perspective out. They are a different answer to a different question, and the difference is one measurable quantity — a parallel projection preserves the ratio in which a point divides a segment, and a perspective projection destroys it by 7% of the segment's drawn length at a comfortable depth, rising to 13% over the range the slider covers.

parallel · parallel horizon = eye level, 1.62 m91.01%correct from 26 cm, at 160 mm widespread 0

The horizon is at eye level — if the picture plane is vertical

The horizon cuts every standing figure at the same fraction of its height however far away it is, which is the most immediately usable fact in the subject. It holds when the camera is level, and a twelve-degree tilt is enough to spread the fractions by more than a percentage point.

construction · eyelevel

Named alongside it

The objects these essays reach for when they reach for this one.

Picture planeAxonometricCamera tiltEye levelHorizonIsometricMidpointOblique projectionOrthographicParallel projectionVanishing point

All concepts