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

costruzione legittima — where it appears

2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.

Also named here as ground line — the same set of essays touches all of them, so they are one junction rather than several.

246VPcorrect from 26 cm, at 160 mm wide34° across

The measuring point, and the step the method leaves out

Laying out equal depths correctly needs a second vanishing point that most treatments never introduce — the one belonging to the diagonals. With it the construction lands on the projected divisions to eighty femtopixels. Without it, depth is placed by judgement and the drawing depicts something nobody chose.

construction · measuring the panelhorizon — the centric point's heightthe section — the eye, the panel, the ground470 px — the viewing distancethree routes agree to 6e-14 pxsection, distance point, and a pinhole camera

Alberti draws a pavement, and chooses where the reader stands

The costruzione legittima of 1435 is exact. Run as a construction — with drawn rays and drawn intersections rather than the formula it turns out to satisfy — it agrees with a pinhole camera to six parts in a hundred trillion of a pixel. And it has one free parameter that the recipe never names, which is the distance from the eye to the panel.

construction · alberti

Named alongside it

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

Centric pointFocal lengthGround lineViewing distancebraccioDiagonal pointHorizonLateral sectionMeasuring pointPicture planePinholeStation point

All concepts