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

Twocentres — the ladder

3 distinct arguments against one idea, from the one that introduces it to the one that assumes the rest.
  1. two eyesno single viewpoint — the rays miss by 0.54 mtwo centres, 1.30 m apart

    A picture with two eyes in it

    Several traditions draw the floor from one place and the people on it from another. This site has said no single camera produces both. What such a picture actually is has a measurement attached: give the rays their world points and ask for the one place they all pass through, and at a stride of separation the best answer misses them by six tenths of a metre.

    rung 2 · conventions
  2. apart by 4.9e-13 pxcorrect from 17 cm, at 160 mm wideone eye again

    The second eye is a shear

    A picture drawn from two eyes is a picture drawn from one, of a different room. The map that puts the second eye away holds the picture plane still point by point and carries one centre onto the other, and the member of its family that matters turns out to be affine — a shear along the line joining the eyes, growing with depth, which is the same operation an oblique drawing performs.

    rung 3 · conventions
  3. the room, as it ismisses by 0.665 mthe room it is consistent withmeets to 1.5e-15 mdecimal places the rays agree tothe picture cannot be askedthe room can

    Counting the eyes needs the room

    How many eyes made a picture is not a question the picture can be asked. Told what the room really measures, the rays refuse to meet and a second eye has been caught; told instead that the room is the one the picture is consistent with, the same rays meet exactly, at the first eye. The refusal is real and it belongs to the room.

    rung 4 · conventions

All ladders