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

Midpoint — 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 centre of the ellipseimage of the centrecorrect from 22 cm, at 160 mm wideoffset 21.1 px

The circle whose centre moves

The image of a circle is an ellipse, and the image of the circle's centre is not the centre of that ellipse. The gap is 3 or 4% of the ellipse's width in an ordinary view — large enough to see, small enough to be dismissed as a slip by anyone not expecting it, and the reason drawn wheels look wrong.

foundations · conic

Named alongside it

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

Picture planeAffine mapAxonometricConicEllipse fitForeshorteningHorizonIsometricline at infinityMinor axisOblique projectionOrthographic

All concepts