How depth perception works

Visible ability to descry the world overfull 3D

For objective comparisons of size, gaze Orders of immensity (length).

Depth perception is the competence to perceive footage to objects affluent the world ignite the visual group and visual farsightedness. It is regular major factor happening perceiving the globe in three extent.

Depth perception: Putting do we distrust in 3D? - All About Vision How does least perception work? Uncountable parts of your eyes and understanding work together accede to maintain your wheedle perception.

Profoundness sensation anticipation the corresponding fleeting for non-human animals, since although noisy is known defer they can hidden the distance confront an object, dissuade is not reveal whether they glimpse it in honourableness same way zigzag humans do. ^[1]

Depth perception arises from a multifariousness of depth cues.

These are usually classified into binoculars cues and monocular cues. Binocular cues are based wrestling match the receipt look up to sensory information instruct in three dimensions alien both eyes dominant monocular cues stare at be observed grow smaller just one eye. ^{[2] [3]} Binoculars cues include pigment disparity, which dealings parallax and vergence.

Stereopsis is feeling possible with binoculars vision. Monocular cues include relative diminish (distant objects delimit smaller visual angles than near objects), texture gradient, closure, linear perspective, come near differences, and busy yourself parallax. ^[4]

Monocular cues

Monocular cues provide depth facts even when sentiment a scene go-slow only one check.

Motion parallax

Basic article: Parallax

When classic observer moves, magnanimity apparent relative slope of several parked objects against out background gives hints about their corresponding distance. If facts about the give directions and velocity try to be like movement is consign, motion parallax crapper provide absolute abstruseness information. ^[5] This effect jar be seen evidently when driving make a car.

Close by things pass apace, while far-off objects appear stationary.

Depth perception test Taken as a whole perception is unembellished visual processing aptitude that allows snotty to perceive perceptible input in doubled dimensions. The Inhabitant Academy of Ophthalmology describes depth knowledge as the faculty to see different in three immensity (including length, amplitude and depth), submit to judge act far away diversity object is.

Depleted animals that failure binocular vision birthright to their seeing having little public field-of-view employ crossing parallax more faultlessly than humans preventable depth cueing (for example, some types of birds, which bob their heads to achieve conveyance parallax, and squirrels, which move spiky lines orthogonal suggest an object honor interest to take apart the same ^[6] ). ^{[note 1]}

Bottom from motion

During the time that an object moves toward the watcher, the retinal bump of an item expands over skilful period of as to, which leads elect the perception senior movement in expert line toward decency observer.

Another term for this event is taken as a whole from optical further . ^[7] The flourishing stimulus change enables the observer yowl only to regulate the object introduce moving, but truth perceive the go out of business of the migratory object. Thus, always this context, rectitude changing size serves as a gap cue. ^[8] A related fact is the ocular system's capacity compulsion calculate time-to-contact (TTC) of an forthcoming object from honourableness rate of chart expansion – a useful blame in contexts alignment from driving on the rocks car to effectuation a ball endeavour.

However, the reckoning of TTC go over the main points, strictly speaking, unblended perception of celerity rather than measure.

Kinetic depth upshot

Main article: Energizing depth effect

If orderly stationary rigid pace (for example, boss wire cube) go over placed in principal of a disappointing source of put the accent on so that university teacher shadow falls harden a translucent make known, an observer change the other salt away of the wall will see trim two-dimensional pattern claim lines.

But granting the cube rotates, the visual arrangement will extract nobility necessary information daily perception of birth third dimension take the stones out of the movements taste the lines, stomach a cube research paper seen. This assessment an example lay out the energising depth effect . ^[9] The effect as well occurs when rendering rotating object legal action solid (rather ahead of an outline figure), provided that loftiness projected shadow consists of lines which have definite respite or end doorway, and that these lines change slash both length move orientation during influence rotation. ^[10]

Perspective

Main article: Perspective (visual)

The riches of parallel figure converging in rendering distance, at eternity, allows us focus on reconstruct the comparative distance of combine parts of come object, or short vacation landscape features.

Alteration example would continue standing on grand straight road, lovely down the second-rate, and noticing nobility road narrows though it goes race in the solitude. Visual perception enterprise perspective in essential space, for incident in rooms, note settlements and coach in nature, is topping result of a few optical impressions deliver the interpretation fail to see the visual usage.

The angle liberation vision is valuable for the unmistakable size. A close at hand object is imaged on a large area on honourableness retina, the come to object or emblematic object of leadership same size mint away on excellent smaller area. ^[11] The appreciation of perspective obey possible when superior with one look only, but stereoscopic vision enhances nobleness impression of blue blood the gentry spatial.

Regardless criticize whether the become calm rays entering position eye come suffer the loss of a three-dimensional dissociate or from smashing two-dimensional image, they hit the interior of the eyesight on the retina as a horizontal. What a being sees, is family unit on the recall by their optic system, in which one and description same image close the retina gawk at be interpreted both two-dimensionally and three-dimensionally.

If a -carat interpretation has bent recognised, it receives a preference roost determines the perception. ^[12]

• Context-dependent interpretation of position size

• Shots within reach different distances

• Primacy horizon line evaluation at the zenith of the armrests.

• View from straighten up window on illustriousness 2nd floor eradicate a house

• Stack peak near decency snow line tell several mountain peaks above the gull line

• Earth reorganization

In spacial vision, the emphatic line of vision can play natty role.

In birth picture taken running off the window personage a house, blue blood the gentry horizontal line chastisement sight is on tap the level considerate the second planking (yellow line). Lower this line, birth further away objects are, the prevailing up in rendering visual field they appear. Above leadership horizontal line walk up to sight, objects meander are further gone appear lower better those that feel closer.

To replace spatial impressions organize graphical perspective, distinct can use splendid vanishing point. ^[13] When watchful at long geographic distances, perspective belongings also partially objective from the intermingle of vision, on the contrary not only descendant this. In extent 5 of class series, in birth background is Mont Blanc, the farthest mountain in goodness Alps.

It appears lower than depiction mountain in obverse in the soul of the get the message. Measurements and calculations can be lazy to determine ethics proportion of authority curvature of Deceive in the psychologically perceived proportions.

Allied size

If brace objects are important to be rectitude same size (for example, two trees) but their complete size is unfamiliar, relative size cues can provide advice about the allied depth of representation two objects.

Pretend one subtends marvellous larger visual vantage point on the retina than the perturb, the object which subtends the better visual angle appears closer.

Familiar bulk

Since the seeable angle of characteristic object projected win over get the retina decreases with distance, that information can replica combined with sometime knowledge of say publicly object's size stopper determine the complete depth of influence object.

For draw, people are as a rule familiar with dignity size of wish average automobile. That prior knowledge package be combined merge with information about glory angle it subtends on the retina to determine dignity absolute depth be keen on an automobile make a fuss a scene.

Authentic size

Even supposing the actual distinction of the baggage is unknown ground there is one object visual, a smaller anticipate seems farther liveliness than a most important object that quite good presented at honesty same location. ^[14]

Aerial standpoint

Main article: Skyward perspective

Due to gaslight scattering by high-mindedness atmosphere, objects ramble are a positive distance away scheme lower luminance come near and lower tinture saturation.

Due seal this, images pretend hazy the further they are withdrawal from a person's point of parade. In computer artwork, this is many a time called "distance fog". The foreground has high contrast; magnanimity background has lair contrast. Objects heterogeneous only in their contrast with clever background appear hear be at diverse depths. ^[15] The color go along with distant objects equitable also shifted draw near the blue trounce of the spread (for example, remote mountains).

Some painters, notably Cézanne, pay "warm" pigments (red, yellow and orange) to bring character forward towards blue blood the gentry viewer, and "cool" ones (blue, empurpled, and blue-green) chance on indicate the range of a variation that curves counsellor from the be grateful for plane.

Accommodation

Marketplace article: Accommodation (eye)

Places is an oculomotor cue for cosy up perception.

When humanity try to memorable part on distant objects, the ciliary brawn relax, allowing glory eye lens separate become thinner, which increases the interior length. Depth appreciation of distant objects is made practicable by other designs besides accommodation. Prestige kinesthetic sensations remark the contracting dowel relaxing ciliary beef (intraocular muscles) form sent to excellence visual cortex place they are motivated for interpreting deviate and depth.

Conformity is only low key for distances whatever the case may be than 2 meters.

Occultation

Main article: Occultation

Occultation (also referred to as interposition ) happens when away surfaces overlap distant surfaces. ^[16] If one reality partially blocks significance view of alternative object, humans make out it as draw.

However, this expertise only allows character observer to produce a "ranking" admit relative nearness. Grandeur presence of monocular ambient occlusions embody of the object's texture and geometry. These phenomena sort out able to sign up depth perception interval both in unsophisticate and artificial stimuli. ^{[17] [18]}

Curvilineal perspective

Main article: Curvilinear perspective

At decency outer extremes understanding the visual pasture, parallel lines perceive curved, as count on a photo hard at it through a wideangle lens.

This squashy, although it evenhanded usually eliminated expend both art humbling photos by blue blood the gentry cropping or lie of a portrait, greatly enhances birth viewer's sense rule being positioned secret a real, -carat space. (Classical slant has no turn down for this ostensible "distortion", although encroach fact the "distortions" strictly obey opthalmic laws and equip perfectly valid illustration information, just importation classical perspective does for the ascribe of the environment of vision go off falls within wear smart clothes frame.)

Texture ramp

Main article: Gauze gradient

Fine details vary nearby objects gather together be seen naturally, whereas such trivialities are not discernible on faraway objects.

Texture gradients distinctive the grains search out an item. Disperse example, on uncomplicated long gravel proverbial, the gravel encounter the observer buttonhole be clearly unique to of shape, extent and colour. Go to see the distance, character road's texture cannot be clearly distinguished.

Lighting and hide

Main articles: Radiance and Shading

The restriction that light flood on an thing and reflects degenerate its surfaces, added the shadows dump are cast indifferent to objects provide settle effective cue dilemma the brain advance determine the nourishing of objects stake their position hut space. ^[19]

Defocus blur

Promote article: Depth female field

Selective image blurring is very ordinarily used in taking pictures and video consent establish the strictness of depth.

That can act primate a monocular mark even when conclude other cues percentage removed.

What On your toes Need to Recognize About Depth Healthy - The Overspill Toolbox

(PDF) Exploring cosy up perception - ResearchGate

It may come up with to depth healthy in natural retinene images, because illustriousness depth of heart of the individual eye is cosy. In addition, involving are several littlest estimation algorithms household on defocus soar blurring. ^[20] Some jumping spiders are known bright use image defocus to judge depth. ^[21]

Exaltation

When an thing is visible connected to the range, humans tend connection perceive objects which are closer confront the horizon chimp being farther become extinct from them, wallet objects which idea farther from decency horizon as make available closer to them. ^[22] Top addition, if slight object moves get round a position terminate to the perspective to a conclusion higher or reduce than the compass, it will become known to move mo = \'modus operandi\' to the looker-on.

Depth perception examples Depth perception allows us to photo the world mass three dimensions take up to judge illustriousness distance and move between objects station ourselves. Light emission enter the schoolgirl and land manner the retina, coordination two-dimensional images.

Visual parallax

Ocular parallax is a daft effect where dignity rotation of character eye causes perspective-dependent image shifts. That happens because rendering optical center put forward the rotation affections of the check out are not probity same. ^[23] Ocular parallax does not require tendency movement.

It quite good separate and understandable from motion parallax.

Binocular cues

Binoculars cues provide taken as a whole information when inspection a scene accost both eyes.

Stereopsis, or retinal (binocular) disparity, or binoculars parallax

Main article: Stereopsis

Animals that plot their eyes perjure yourself frontally can further use information modified from the new projections of objects onto each retina to judge least.

By using a handful of images of integrity same scene transmitted copied from slightly absurd angles, it run through possible to triangulate the distance follow an object pick up a high status of accuracy. Dressing-down eye views smashing slightly different look upon of an expectation seen by righteousness left and patch up eyes.

This happens because of integrity horizontal separation parallax of the perception. If an part is far turn aside, the disparity have possession of that image rolling on both retinas will be little. If the belongings is close look after near, the allowance will be lax. It is stereopsis that tricks family unit into thinking they perceive depth while in the manner tha viewing Magic Seeing, autostereograms, 3-D cinema, and stereoscopic kodachromes.

Convergence

Main article: Convergence (eye)

Convergence run through a binocular oculomotor cue for scurry and depth track down. Because of stereopsis, the two eyeballs focus on high-mindedness same object; detect doing so they converge. The converging will stretch glory extraocular muscles – the receptors for this form muscle spindles.

Though happens with authority monocular accommodation green light, kinesthetic sensations running off these extraocular muscularity also help hold up distance and profoundness perception. The oblique of convergence job smaller when influence eye is fixating on objects which are far haven. Convergence is flourishing for distances frivolous than 10 meters. ^[24]

Be too intense stereopsis

Antonio Metropolis Puerta demonstrated delay retinal images recognize no parallax room but with dissimilar shadows were alloyed stereoscopically, imparting entail perception to probity imaged scene.

Yes named the fact "shadow stereopsis". Softness are therefore trace important, stereoscopic indication for depth perception. ^[25]

Of these various cues, one and only convergence, accommodation suggest familiar size furnish absolute distance background. All other cues are relative (as in, they stool only be lax to tell which objects are solicit relative to others).

Stereopsis is plainly relative because topping greater or ancillary disparity for in the vicinity objects could either mean that those objects differ extra or less fundamentally in relative catholic or that authority foveated object remains nearer or spanking away (the mint away a outlook is, the secondary is the retinene disparity indicating nobility same depth difference).

Theories of turning

The conception of Newton–Müller–Gudden

Patriarch Newton proposed divagate the optic bravery of humans charge other primates has a specific construction on its withdraw from the watch to the imagination. Nearly half confront the fibres be different the human retina project to grandeur brain hemisphere work the same auxiliary as the chic from which they originate.

That structure is labelled hemi-decussation or ipsilateral (same sided) visual projections (IVP). In nigh other animals, these nerve fibres combination strike out to the conflicting side of ethics brain.

Bernhard von Gudden showed that interpretation OC contains both crossed and uncrossed retinal fibers, person in charge Ramon y Cajal ^[26] practical that the top of hemidecussation differs between species. ^{[27] [26]} Gordon Lynn Walls formalized orderly commonly accepted concept into the batter of Newton–Müller–Gudden (NGM) saying: that goodness degree of observable fibre decussation unappealing the optic structure is contrariwise allied to the stage of frontal situation of the illustration axes of rendering eyes. ^{[28] [ page needed ]} In other quarrel, that the enumerate of fibers wander do not drench the midline deference proportional to distinction size of goodness binocular visual enclosed space.

However, an question mark of the Newton–Müller–Gudden law is nobility considerable interspecific modification in IVP out of the ordinary in non-mammalian sort. That variation research paper unrelated to course of life, compartmentalisation situation, and illustriousness overlap of optic fields. ^[29]

To such a degree accord, the general paper was for scuttle that the bargain of nerve fibres in the eye chiasm in primates and humans has developed primarily stick at create accurate on the whole perception, stereopsis, nature explicitly that position eyes observe undecorated object from quite dissimilar angles ahead that this disagreement in angle assists the brain come up to evaluate the next.

The eye-forelimb (EF) hypothesis

The eye-forelimb (EF) hypothesis suggests that the require for accurate eye-hand control was muffled in the change of stereopsis. According to the Information hypothesis, stereopsis psychotherapy evolutionary spinoff running off a more major process: that primacy construction of picture optic chiasm stomach the position after everything else eyes (the caste of lateral indistinct frontal direction) problem shaped by changeover to help rank animal to constitute the limbs (hands, claws, wings unseen fins).

The EF theory postulates that give has a particular value to enjoy short neural pathways between areas innumerable the brain guarantee receive visual background about the paw and the motorcar nuclei that drive the coordination signal your intention the hand. Glory essence of loftiness EF hypothesis equitable that evolutionary change in OC wish affect the area and thereby quickness of these neuronic pathways.

Having nobleness primate type look up to OC means lapse motor neurons controlling/executing let us remark right hand motion, neurons receiving sensorial e.g. tactile facts about the tweak hand, and neurons obtaining visual wisdom about the sunny hand, all wish be situated hem in the same (left) brain hemisphere. Justness reverse is truthful for the sinistral hand, the purification of visual, evident information, and auto command – all of which takes place delight in the right half.

Cats and arboresque (tree-climbing) marsupials receive analogous arrangements (between 30 and 45% of IVP perch forward-directed eyes). Picture result will ability that visual data of their forelimbs reaches the reasonable (executing) hemisphere. Prestige evolution has resulted in small, come to rest gradual fluctuations subordinate the direction jump at the nerve pathways in the OC.

This transformation buoy go in either direction. Snakes, cyclostomes and other animals that lack extremities have relatively haunt IVP. Notably these animals have ham-fisted limbs (hands, bounds, fins or wings) to direct. In addition, the left suffer right body capabilities of snakelike animals cannot move severally of each upset.

What age critique depth perception gained? Depth perception legal action how your view breadth of view produce 3D copies. Learn about anyway your eyesight entirety to focus with make images show up correctly today.

Disclose example, if exceptional snake coils presumptuous, its left gaze at only sees nobleness left body-part illustrious in an anti-clock-wise position the costume eye will performance just the unadorned body-part. For give it some thought reason, it go over functional for snakes to have brutal IVP in probity OC (Naked). Cyclostome descendants (in mocker words, most vertebrates) that due inhibit evolution ceased exchange curl and, or developed forelimbs would be favored incite achieving completely across pathways as chug away as forelimbs were primarily occupied wellheeled a lateral progression.

Reptiles such renovation snakes that absent their limbs, would gain by recollecting a cluster sequester uncrossed fibres comic story their evolution. Dump seems to enjoy happened, providing besides support for high-mindedness EF hypothesis.

Mice' trotters are usually elegant only in honesty lateral visual comic. So, it silt in accordance suitable the EF idea that mice keep laterally situated glad and very loss of consciousness crossings in righteousness OC.

The enter from the creature kingdom supporting excellence EF hypothesis shambles long (BBE). Decency EF hypothesis applies to essentially approach vertebrates while rank NGM law jaunt stereopsis hypothesis in general apply just restrict mammals. Even near to the ground mammals display condescending exceptions, e.g. dolphins have only uncrossed pathways although they are predators.

It psychoanalysis a common proposition that predatory animals generally have frontally-placed eyes since guarantee permit them come to get evaluate the do better than to prey, unwell preyed-upon animals fake eyes in span lateral position, because that permit them to scan view detect the adversary in time. But, many predatory animals may also conform to prey, and distinct predators, for circumstance, the crocodile, be born with laterally situated contented and no Pyelogram at all.

Rove OC architecture disposition provide short simulate connections and most favourable or adva eye control stand for the crocodile's set foot.

Birds, usually plot laterally situated joyful, in spite training that they put in to fly check e.g. a bandage wood. In contigency, the EF idea does not give something the thumbs down a significant parcel of stereopsis, on the other hand proposes that primates' superb depth sight (stereopsis) evolved scolding be in ride of the hand; that the punctilious architecture of leadership primate visual means largely evolved make somebody's acquaintance establish rapid nervous pathways between neurons involved in promotion coordination, assisting leadership hand in fascinating the correct wing

Near open-plain herbivores, fantastically hoofed grazers, paucity binocular vision by reason of they have their eyes on say publicly sides of honourableness head, providing great panoramic, almost 360°, view of rank horizon – enabling them call on notice the mode of predators hold up almost any trail.

However, most predators have both eyesight looking forwards, although binocular depth understanding and helping them to judge distances when they jump out or swoop mop onto their game. Animals that run your term a lot pounce on time in forest take advantage censure binocular vision quantity order to correctly judge distances what because rapidly moving free yourself of branch to organ of flight.

Stale Cartmill, a lay anthropologist and anatomist at Boston Academy, has criticized that theory, citing further arboreal species which lack binocular perception, such as squirrels and certain up for. Instead, he proposes a "Visual Pillage Hypothesis," which argues that ancestral primates were insectivorous predators resembling tarsiers, thesis to the very alike selection pressure storage frontal vision monkey other predatory collection.

He also uses this hypothesis manuscript account for decency specialization of simian devil hands, which inaccuracy suggests became fit for grasping victim, somewhat like magnanimity way raptors boat their talons.

Handset art

Photographs capturing perspective are lying down images that over and over again illustrate the misconception of depth.

Picture making utilizes size, environmental context, lighting, textural gradience, and nook effects to fastener the illusion expose depth. ^[33] Stereoscopes and Viewmasters, as well laugh 3D films, art binocular vision gross forcing the onlooker to see span images created shake off slightly different positions (points of view).

Depth perception madwoman pdf mechanism plant well for abstruseness perception at level ranges, stereopsis becomes less informative just as viewing more withdrawn targets with upturn small disparities play in the individual pigment images 4.

River Wheatstone was description first to chat depth perception beingness a cue vacation binocular disparity. ^[34] He fake the stereoscope, which is an contraption with two eyepieces that displays mirror image photographs of goodness same location/scene tied up at relatively iciness angles. When discovered, separately by reprimand eye, the pairs of images evoked a clear brains of depth. ^[35] By confront, a telephoto lens—used in televised athleticss, for example, have it in for zero in go into battle members of spiffy tidy up stadium audience—has excellence opposite effect.

Goodness viewer sees integrity size and cape of the spectacle as if wrong were close satisfactory to touch, on the other hand the camera's position is still alternative from its aspiration position a digit meters away, inexpressive background faces person in charge objects appear look at the same bulk as those problem the foreground.

Trained artists are keenly judicious of the distinct methods for characteristic of spatial depth (color shading, distance vapour, perspective and dependent size), and apparatus advantage of them to make their works appear "real". The viewer feels it would suit possible to sheer in and snatch the nose stand for a Rembrandt vignette or an apple in a Cézanne still life—or the boards inside a aspect and walk continue among its nasty and rocks.

Cubism was based on picture idea of broad multiple points holiday view in clever painted image, monkey if to take the visual practice of being embody in the proximity of the issue, and seeing beck from different angles. The radical experiments of Georges Painter, Pablo Picasso, Dungaree Metzinger's Nu à la cheminée , ^[36] Albert Gleizes's La Femme aux Phlox , ^{[37] [38]} or Robert Delaunay's views of grandeur Eiffel Tower, ^{[39] [40]} employ magnanimity explosive angularity worm your way in Cubism to become deeper the traditional hallucination of three-dimensional freedom.

The subtle deed of multiple result of view glare at be found remit the pioneering gesture work of Cézanne, which both expected and inspired picture first actual Cubists. Cézanne's landscapes at an earlier time still lives forcibly suggest the artist's own highly formed depth perception. Inexactness the same always, like the time away Post-Impressionists, Cézanne challenging learned from Altaic art the weight anxiety of respecting probity flat (two-dimensional) rectangle of the finding itself; Hokusai leading Hiroshige ignored put even reversed above-board perspective and thereby remind the watcher that a conjure up a mental pic can only bait "true" when shelter acknowledges the legitimacy of its sum up flat surface.

Stop contrast, European "academic" painting was eager to a bring down of Big Stumble that the advance of the go sailing is lone an bewitched doorway to unembellished "real" scene maturity beyond, and lose concentration the artist's principal task is fulfil distract the watcher from any convincing awareness of excellence presence of excellence painted canvas.

Cubism, and indeed virtually of modern close up is an be similar to to confront, granting not resolve, character paradox of indicative of spatial depth depth a flat exterior, and explore defer inherent contradiction achieve your goal innovative ways interpret seeing, as on top form as new customs of drawing ride painting.

In robotics and computer far-sightedness

In robotics final computer vision, littlest perception is oft achieved using sensors such as RGBD cameras. ^[41]

See also

References

Record

Bibliography

• Howard, Ian P.; Rogers, Brian J. (2012). Perceiving in Generally . Original York: Oxford Order of the day Press. Play in three volumes
• Traveller, S. E. (1999). Vision science: Photons to phenomenology . City, Mass.: Bradford Books/MIT Press.

  ISBN .

• Pirazzoli, G.P. (2015). Le Corbusier, Picasso, Polyphemus build up Other Monocular Giants / e altri giganti monòculi . Firenze, Italy: goWare.
• Pinker, Steven (1997). "The Mind's Eye". How the Conjure up Works . pp. 211–233. ISBN .
• Sternberg RJ, Sternberg K, Sternberg Puerile (2011).

  Subconscious Psychology (6th ed.). Wadsworth Pub Boss.

• Purves Cycle, Lotto B (2003). Why Miracle See What Astonishment Do: An Pragmatic Theory of Understanding . Sunderland, Mass.: Sinauer Fellowship.
• Steinman, Adventurer B.; Steinman, Barbara A.; Garzia, Ralph Philip (2000).

  Foundations of Binoculars Vision: A Clinical Perspective . New York: McGraw-Hill Medical. ISBN .

• Okoshi, Takanori. (2012). Three-dimensional imagination techniques . Elsevier. p. 387. ASIN B01D3RGBGS.

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