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0 5 10 15 20 0 20 40 60 how far off the fovea the line passes (degrees) departure from a straight chord, in degrees of visual angle schematic eye concentric retina a line spanning ±65° of azimuth 17.30° at 40° eccentricity
Retina
1
The eye is a picture surface too
1 essay · curved
what was drawn the solid it depicts — reading 1 of 2 x y z looked at 0.00° off the normal cube edge 1.0000 of the drawn unit residual 1e-16
Reversal
3
The drawing does not say which corner is nearer
1 essay · parallel
the true profile exact marks rms 4.9e-15 m
Scan
1
A shadow edge read as a profile
1 essay · light
horizon the point its shadow correct from 22 cm, at 160 mm wide rays cross at 28.5° · recovered to 9e-16 m
Shadowdepth
4
The lamp is the second eye
1 essay · light
35.08° correct from 16 cm, at 160 mm wide two maps, meeting at 35.08°
Shadowseam
3
A shadow across an edge
1 essay · light
a dished floor · truly 0.060 0.0600 a flat floor · truly 0 0 a floor with a 60 mm step · truly 0 0.4820 one lamp, one ring occluder the step reports 0.482
Shapefit
5
The curvature a shadow reports
1 essay · metrology
one direction — the pole — drawn as the whole of this edge 8° cap at the pole: ×9.2 the same cap, 20° off axis: ×0.646 both caps hold 201 square degrees of sky ×14 between them
Singularity
1
A pole is a line
1 essay · curved
-50 0 50 0.500 1 distance to the thing being stitched (log₁₀ metres) what the stitch leaves behind (px) 2.86 m 80 mm baseline zero at one depth each
Stitchdepth
3
A rig is right on one surface
1 essay · curved
plane every line — cylinder one parameter · parallel no meeting point stereographic one parameter · concurrent they meet to 1e-12 equirect. one parameter · parallel no meeting point 3 of 4 keep a curve the signature has three values, not eight
Straightfamily
5
The lines a surface leaves alone
1 essay · curved
horizon isometric — the same drawing, moved perspective — a different drawing correct from 23 cm, at 160 mm wide parallel: 4e-14 px · perspective: 87.2%
Translation
2
Nothing moves when the object does
1 essay · parallel
the picture plane, in plan to the observer, 208 px further down correct from 12 cm, at 160 mm wide station 520 px
Tworules
1
Two rules for one pavement
1 essay · construction
horizon — the image of the line at infinity vanishing point at x = 1464 — off the frame correct from 26 cm, at 160 mm wide 34° across
Vanishing
1
Where parallel lines meet
1 essay · foundations
barrel vault eye · 1.62 m on the floor 1e-12 mm on the vault 529.4 mm worst miss of the best homography, log scale vault radius 4.0 m 7.7% of the extent, against 4e-14%
Vaultanamorph
4
The ceiling that is not a plane
1 essay · viewing
the eye the design is for the camera correct from 14 cm, at 160 mm wide recovered to 2.5e-14 m
Wallrecovery
5
The wall under the paint
1 essay · metrology
54 px 69 px 84° across 27% wider at the edge
Widefield
3
Wide angle is not distortion
1 essay · viewing
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