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• A height, out of one photograph
• Flattening a façade out of the photograph
• How wrong a measurement from one picture can be
• The one thing a single view cannot give
• The wall under the paint
• The curvature a shadow reports
• One picture of a ball
• Two pictures of a ball
• The dish no outline reaches
• An area, out of one photograph
• Counting is a measurement
• An angle on the ground
• The answer is an ellipse
• Which reference to measure from
• The floor a better camera cannot reach
• Five facts that close the same gap
• The plan hidden in the photograph
• Where each closure enters the stratification

• A mirror is a second camera
• A shadow is a second projection
• Where shadows vanish
• The penumbra is the lamp's image
• The shadow of a ball is a conic
• The lamp, out of the picture
• A shadow can be un-cast
• A wall does not get darker as it goes away
• A lamp lights less than half a ball
• The floor that is not a plane
• A shadow across an edge
• The lamp is the second eye
• A light far enough away
• Two lamps and one map
• The ball stands at a focus
• A wire with a corner in its shadow
• The edge of a shadow is drawn on the object
• A hole is not preserved
• A shadow across a second object
• The residual has a shape
• The floor is a choice of coordinates
• The lamp comes out in rays and not in plan
• The corners a floor cannot add
• A floor is read along curves
• How many lamps a drawing has
• The distance at which two lamps part
• A floor cannot fake a second lamp
• The drawing does not run out of lines
• Counting shadows is not counting lamps
• A lamp behind the camera
• The arrangement the count cannot see
• The lamp's size over its distance, and nothing else
• The lamp a low shadow cannot locate
• A soft shadow on a curved floor is not the lamp's image
• How many lamps make one lamp
• What a point in shadow can see of the sky
• Where a shadow splits in two
• How many shadows determine the object
• A dent breaks the terminator
• A shadow edge read as a profile
• The lamp and the floor cannot both be recovered

• Alberti draws a pavement, and chooses where the reader stands
• Brunelleschi drilled a hole in his panel
• One, two and three point are one construction
• The distance point is the viewing distance, drawn
• The horizon is at eye level — if the picture plane is vertical
• The measuring point, and the step the method leaves out
• The horizon, and the fraction
• The bay repeated by a straightedge
• Straightening does not move the eye
• The plane is a choice
• The ramp has its own horizon
• Carrying a height across the room
• A picture with nothing straight in it
• Seven is not a power of two
• The circle in the square wants a number
• The line every nosing is on
• Three-point, laid out with a straightedge
• A drawing has three horizons
• The arc every eye stands on
• The quadrilateral no rectangle casts
• The proportion is the assumption
• Three procedures, one panel
• Four marks before anything is said
• The slip that leaves no trace
• One hand step each
• Stepped, or measured from the zero
• What a panel says about its maker
• Dividing to a point off the board
• The stair that turns has a vanishing point that moves
• A measuring point for a ramp
• Figures on a street that slopes
• The bays that are not equal
• What a straightedge reaches on a receding line
• Two rules for one pavement
• The centre of the picture is not the centre of the paper
• Copying square by square
• The hook is the centre, and the eye is not

• An anamorph at true size, on paper
• Anamorphosis is only a viewpoint
• The cylindrical mirror unbends it
• The point you have to stand at
• When the picture surface is not flat
• Wide angle is not distortion
• Standing in the wrong place
• A floor anamorph is three numbers
• The marks name the place, not the height
• The ceiling that is not a plane
• A set cut for one eye
• Where the anamorph still works
• The room the eye may stand in
• An anamorph has one eye
• The design that outruns the floor
• The anamorph that crosses a corner
• The height a flat floor cannot give
• A stair does not use all its faces
• What an eye can paint
• Facing the reader is not being reachable
• The eye that reaches the most
• A design that lands in two rooms
• The stretch decides the band
• One flight, two pictures
• A fold names the height
• A flight that has ends

• Every fisheye is a different rule
• No picture surface keeps everything
• Stereographic keeps every angle, and only stereographic
• The cylinder, and the price of going all the way round
• What a 360-degree photograph actually is
• The arcs a curvilinear drawing uses
• One parameter between two surfaces
• Conformal is not undistorted
• Six flat pictures of everything
• The lines a surface leaves alone
• Undoing a picture made on a curve
• How well the floor has to be known
• The floors that unroll
• The third column is area
• Counting cloud by counting pixels
• The pivot that is not the eye
• The parallax you cannot shoot away
• The camera that is a cylinder
• A rig is right on one surface
• The surface a screen wants
• A picture that can be printed
• Three conditions, and three prices
• Drawn for the cylinder, shown on the cylinder
• Where a surface spends its pixels
• The horizon's shape belongs to the surface
• A pole is a line
• Which rule a fisheye obeys, from straightness alone
• The kink at a seam
• The arcs the five-point construction actually draws
• The eye is a picture surface too
• The hole a rig cannot fill
• Shot on one surface, shown on another
• A projector that is not at the dome's centre

• Parallel projection is not primitive perspective
• The eye taken to infinity
• What isometric actually means
• Which axis scales are possible
• Any three lines you draw are a cube
• Oblique is a shear, and the shear is the whole system
• A ruler on an isometric drawing
• The drawing does not say which corner is nearer
• The ellipse the drawing office draws
• Three views do not fix the solid
• The view that makes a line a point
• Nothing moves when the object does
• The true shape of a cut
• What two parallel views leave free
• The dimetric the set square draws
• What one oblique drawing shows
• A circle off the coordinate planes
• The shadow rules that hold here
• The drawing that gives the solid back
• The ball a drawing does not draw round
• No view draws a curved plate true
• The drawing and the development
• A drawn fold has a phantom
• Two outlines are two curves
• Two distances to infinity
• A picture with no eye
• Nothing moves along the direction
• One face, one scale

• The circle whose centre moves
• Recovering the camera from the picture it drew
• What a projection destroys
• Where parallel lines meet
• A projection of a projection
• The diagonals find the middle
• Two triangles and the line nobody drew
• What one picture of a plane determines
• Four lines have a cross-ratio
• The centre, got back out of the picture
• An angle is a cross-ratio
• The two points a picture hides
• One conic calibrates the camera
• What a flat map leaves alone
• Three constructions, one map
• The conic a circle becomes
• Two lines at infinity
• Five marks and the sixth
• Two circles, one picture
• The polar with a straightedge
• The ball at the edge of the frame
• Every quadric has one outline
• A line is a space of its own
• The map a row of posts is
• Perpendicular is a pairing
• An error with two terms
• What a null result is worth in decades
• The ladder of assumptions is a ladder of conditioning
• The bias out of reach
• A floor with a referent
• A point and a line are one object
• The horizon has a pole
• Five tangents name the same conic
• Desargues read the other way
• The quadrilateral that finds the middle
• Four points on a conic look the same from anywhere on it
• Three conics are one conic and a choice of horizon
• Pascal's line, and the theorem underneath Pappus
• The triangle a camera cannot move
• A curved surface made of straight lines
• A line is a closed curve
• Three kinds of map on a row of posts
• Every projectivity is two perspectivities
• The picture contains what is behind the camera
• The theorem that is obvious one dimension up

• The cube that is a box
• Dividing depth by eye
• The sixty-degree cone of vision
• The third point put where it looks right
• Both vanishing points on the paper
• The forty-five degree shadow
• Measured down from the waterline
• Which way the drawn circle leans
• The rule that draws another room
• Six tangents and the point nobody drew
• A mirror that is not parallel to the wall
• The minor axis is not the axle
• A cylinder has two different ends
• A square plan is not a cube
• The rule is exact for a floor that lengthens
• A tapered part meets at its apex
• A turned cube punishes the eye, not the construction
• A straightedge convicts the rule on five braccia

• A lens destroys the invariant
• Fitting a lens from straightness alone
• Straight lines that are not
• The eye is a place, not a point
• The principal point is not the centre
• The lens a pavement can hide
• The hole a scene actually sees
• The lines that calibrate a lens
• A tilted sensor is not a distortion
• A barrel model folds at a radius it sets itself
• The entrance pupil walks with the angle
• A model that inverts has a horizon instead of a fold
• Focusing moves the pivot past its best place
• The response is at the ends and the information is not
• No design separates the two coefficients
• A known target sharpens the fit and does not separate it
• A stereographic fisheye is a division model
• A tilted target pays for its tilt in perspective

• A picture through water has no viewpoint
• The port that is not there
• The sky inside a cone
• What a ray does at a surface
• What survives a pane of glass
• The dome knows its offset in units of itself
• A pane gives a product before it gives two numbers
• One surface, two images
• A ball of water has no eye either
• A straight stick in water is a kink and a curve
• A point under water has two depths
• A wedge of glass turns the camera behind it
• The stick a stereo pair puts back
• The wedge recovered with the camera
• The residual does not warn
• A fit weighted by the miss trusts only the surface
• A wedge moves the centre, not the lens
• A third eye sees the water the pair cannot

• The image of the other eye
• A point is a line over there
• Eight points and the basis they are read in
• Four cameras fit, and one of them can see
• Two views give shape and no size
• A flat scene fixes no second eye
• How flat is flat enough
• Seven marks, three answers
• The surface two pictures cannot separate
• An ambiguity is not an uncertainty
• An epipole in the picture leaves a blind disc
• The two pencils keep one number
• Rectification is a family, not an operation
• Two marks off a known plane find the other eye
• Seeing the scene fences in the plane at infinity
• A parallax length is a height over a depth
• A sway gives the blind centre a depth, not a good one
• A plane's coefficient reaches as far as its parallax

• Depth is a reciprocal
• The range a pair cannot see past
• Two rays that do not meet
• A turn of the head is not a step sideways
• A wrong match is not a small error
• The depth a pair calls zero
• The midpoint is a choice of ruler
• Whole pixels cut space into shells
• Both coordinates agree on a circle and a line
• Raise the gaze, and the line is gone
• A mismatch on its own line needs a third eye
• Vergence moves the shells and does not respace them
• A third eye that lands on the next post
• A third ray is worth what its picture is worth
• The second disparity cuts cells
• Rectifying a pair spends what its epipolar lines lean
• A sliding pair keeps its line only near the middle
• A rectification's free shift is free only near the pair

• The track and the scene together
• Seven numbers no picture can name
• A chain and an adjustment
• Where the adjustment stops
• Another picture of the same sweep
• Far enough away, a pair is one eye
• An uncertainty is quoted from something
• The eighth held number bends the scene
• A narrow view keeps a second answer, inside out
• A scale chain leans rather than wanders
• Closing a loop mends its ends
• The spread a point gets
• A loop's far side is a length
• A survey is trusted at its own accuracy, unless its error has a shape
• A start needs the sign of its depths, not their size
• The cameras decide where a narrow view settles
• A scale bar is worth its ends, not its tape
• Split the track and the needles turn

• A scroll is a camera that moves
• A straight line in a scroll is a hyperbola
• The centre a scroll does not have
• A scroll is not a panorama
• Three distances in one landscape
• A map along, and a picture across
• A landscape that changes its rule halfway up
• A pond in a scroll is not an ellipse
• A scroll through two slits ranges in a straight line
• A scroll round a bend loses its straight-line depth
• A scroll can be asked its own radius
• The stations are also a staircase
• A seam breaks direction, not size
• A shadow decides which landscape it is
• Where a seam is allowed to go
• A seam that bends trades a turn for a gap
• A scroll of a climbing road measures its grade
• An eye that pitches with the road keeps its rows

• What the removed roof buys
• Measuring a room off the page
• A picture with no size–distance signal
• Assembled from several views
• A picture with two eyes in it
• Two grounds, and what the second one costs
• A parallel floor under a perspective room
• Counting the eyes needs the room
• The second eye is a shear
• The same person, twice on one panel
• Size that means rank
• The pond with its trees laid flat
• What survives being copied
• A picture in bands
• A carpet and the people on it
• The workshop that throws drawings away
• Two stations in one picture
• A grid on the wall is a scale without a projection
• Higher on the page, and where that stops being true
• The room a divergent picture is a photograph of
• No solid casts an aspective figure
• What a removed wall costs that a removed roof does not

• The picture whose lines spread
• An inverse perspective is a leaning plane
• Each system answers its own question
• What perspective gave up
• A centre and a measure are exclusive
• A yes in the table is a price
• A page is bounded by a divide, not a centre
• Four surfaces, and no one camera that draws them
• A camera count needs a tolerance
• One camera means one horizon, not one point
• The tenth row has neither
• The exclusion is two conditions, not ten rows
• The rows under a splay measure the bays, not the lean
• The rows count hands, not cameras
• A vanishing line with a slope in it
• A tiring hand draws a different habit
• A tiring panel keeps its order, not its direction
• A strip keeps its ratio, not the end it began

• The divide is postponed, not avoided
• What happens behind the eye
• The precision a depth buffer has left
• A pixel is not a point
• A texture does not interpolate on the page
• Four numbers and a window
• A tile is an off-centre frustum
• The near plane can be any plane
• One plane is nearly free
• A curved screen is eight flat ones
• One depth per sample is not enough
• Along a line of constant depth the page is affine
• A point at infinity is an ordinary vertex
• A shadow map's texels land by two distances and two cosines
• A tilted span walks a staircase
• One warped shadow map, and what it cannot reach
• A texture reaches the horizon as a rate
• One homography makes a shadow map the eye's picture

• A focal length is not an angle
• Stepping closer is not zooming
• Every row is a different camera
• A frame is an interval
• The pixel that is not square
• The centre has an area
• The sharp band is a decision
• A pupil sees around an edge
• The corner sees an ellipse
• The disc and the streak
• Focusing is a zoom
• A turning frame can be straightened; a travelling one cannot
• A dolly zoom is a step and a zoom, and they meet at one depth
• A close picture carries its own distance
• Turning and travelling blur different worlds
• A camera on a bend is sharp on a circle
• A dolly zoom off the axis keeps a line, not a plane
• A frame's shear knows travel only over depth

• The screen sets the distance
• A wide field on a small screen
• Two pictures on one screen
• The render is distorted on purpose
• A projector is a camera run backwards
• Turning the cameras inwards
• The screen is a picture surface too
• The screen that names the seat
• The seats a screen will accept
• One picture and three people
• What the two eyes are sent
• The evenness a curve buys
• A projector in the viewer's eye
• Matching buys one seat
• The distance at which the eyes part
• A stereo picture is drawn for a level head
• A curved screen tilts a stereo pair both ways at once
• Drawing for the curve removes the curve, not the nearness

• A curved mirror has no eye
• Where the focus went
• The one shape that focuses
• A mirror ball is an equal-area fisheye
• The cone that reads the floor
• A mirror ball does not know its size
• The caustic is the mirror's own ruler
• A fitted radius is wrong before it is uncertain
• One shutter, two views
• Two matches are enough
• Square to the camera is the worst mirror
• Two mirrors make one turn
• The corner that answers every eye
• Two mirrors show fewer images than they make
• Two mirrors are three cameras
• Closer than they appear, by a factor with a number in it
• A symmetric object is its own stereo pair
• Two people between mirrors see each other equally often