Concept
Free parameter — where it appears
2 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
The cube that is a box
The two-point cube every book teaches has a step it supplies no construction for. Place the two far edges symmetrically and the drawing depicts a cube for free; place them eight points apart — a difference invisible on the page — and it depicts a box 1.4 times shallower than it is wide.
Each system answers its own question
A comparison in which every system wins its own column proves nothing if the columns were chosen after the systems. The test that makes it a result is whether any system wins something it was not designed for — and two of them do.
Named alongside it
The objects these essays reach for when they reach for this one.
Axis scaleBack projectionConformalCross ratio testDemonstrationDepicted rectangleDrawing systemFocal lengthFocal recoveryHorizoninstrument limitMeasuring point