Slide 1Tell me why these pictures bizarre?Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Why did Leonardo become so famous?1469Slide 24Slide 25What I think:Leonardo found two tricksLeonardo used lots of pictorial cues to depict depthSlide 29Slide 30Linear perspectiveSlide 32Other quintessential Renaissance men areSlide 34How did they reproduce the world?Slide 36Monocular pictorial cuesOcclusionSlide 39Slide 40Slide 41Slide 42Slide 43Slide 44Texture gradientSlide 46Slide 47Visual IllusionsSlide 49Slide 50Slide 51Slide 52Slide 53What makes these pictures surreal?Slide 55Any idea?My guess:Slide 58Slide 59Slide 60Slide 61Slide 62How to make an Escher figure.Slide 64Slide 65Other cuesSlide 67Binocular Depth InformationWhy do we have two eyes?Slide 70Something to do with evolution?What eyes are for?Why are two eyes better than one eye?We got two ears, two nostrils as well.How do we obtain depth information using two eyes?Binocular depth cuesSlide 77Slide 78Slide 79Slide 80Slide 81Slide 82Slide 83Where?Key termsch 8 1Sensation & PerceptionCh. 8: Perceiving depth and size© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Main topicsMonocular depth cuesBinocular depth cuesVisual illusionThe physiology of depth perceptionch 8 2Tell me why these pictures bizarre?ch 8 3Escher:Ascendingch 8 4Belvedere: Escherch 8 5Red Ants: Escherch 8 6Relativity: Escherch 8 7Up and Down: Escherch 8 8Waterfall: Escherch 8 9ch 8 10De Chiricoch 8 11Why do these paintings evoke a strange feeling?ch 8 12Leonardo da Vinci (1452-1519)There has never been an artist who was more fittingly, and without qualification, described as a genius. Like Shakespeare, Leonardo were from an insignificant background and rose to universal acclaim. Leonardo was the illegitimate son of a local lawyer in the small town of Vinci in the Tuscan region….Mona Lisa (1503)ch 8 13The Dreyfus Madonna: da Vinci 1469ch 8 14Why did Leonardo become so famous? One secret:ch 8 15The Last Supper: da Vinci, 1498ch 8 16The virgin of the rocks: da Vinci, 1483-1486ch 8 17Madonna Litta: (da Vinci)1490-1491ch 8 18The Santa Trinita Madonna: Cimabue (1260/80)ch 8 19Coronation of the virgin altarpiece from San Domenico: Fra Angelico, 1434ch 8 20The presentation of the virgin: Giotto, 1305ch 8 21Madonna in Glory: Giotto, 1311ch 8 22Why did Leonardo become so famous?•Or what made Leonardo’s pictures so special?ch 8 2314691260/80131114342000Historical depiction of Madonnach 8 2414691260/80131114342000Historical depiction of Madonnach 8 25ch 8 26What I think:•Everything before Leonardo was very flat.•These pictures were so crisp clear.•No ambiguity.•Leonardo made things more ambiguous.ch 8 27Leonardo found two tricks•To depict distance, L used (but not W)–Linear perspective–Atmospheric perspectivech 8 28Leonardo used lots of pictorial cues to depict depthch 8 29Atmospheric perspectiveThings get vague when they are away.ch 8 30Things get smaller when they are away.ch 8 31Linear perspectiveThings get smaller when they are away.ch 8 32Linear perspective•Linear perspective is very “Renaissance.”•Renaissance  humanism  free from feudalism (religious bigotry)•Put a person at the center of the world.–Not religious authoritych 8 33Other quintessential Renaissance men are•Descartes (1590-1650)–I think therefore I am. (“I” is the center).•Linear perspective is a pictorial version of “I think therefore I am.” (my idiosyncratic interpretation).•Why?ch 8 34•Linear perspective is about putting yourself at the center of the physical world.• and arrange everything else based on that center.•It is about reproducing the relationship between you, the painter, and the other objects in the world in pictorial space.ch 8 35How did they reproduce the world?•Pictorial cues:ch 8 36•This simple trick was very difficult to find before Renaissance.•Because religion was at the center of everything.ch 8 37Monocular pictorial cues•Occlusion•Relative height•Relative size•Familiar size•Atmospheric perspective•Linear perspectivech 8 38Occlusionch 8 39Relative heightch 8 40Relative sizech 8 41Atmospheric perspectivech 8 42ch 8 43ch 8 44ch 8 45Texture gradientch 8 46ch 8 47•These cues are something you notice everyday in the physical world.•The visual system uses these cues and generates depth perception naturally. –You don’t need to think about them. They are just there.ch 8 48Visual Illusionsch 8 49(A)(B)(A)(B)ch 8 50ch 8 51ch 8 52ch 8 53Tell me why these pictures bizarre?•Any idea?ch 8 54What makes these pictures surreal?ch 8 55What makes these pictures surreal?ch 8 56Any idea?ch 8 57My guess:•These pictures deliberately violate pictorial cues. which evokes a strange feeling. these pictures depict impossible scenes by reversing depth relations.ch 8 58•Violating some depth cues–Deliberately introducing contradictory depth information.ch 8 59What makes these pictures surreal?Violating linear perspectivech 8 60ch 8 61ch 8 62ch 8 63How to make an Escher figure.ch 8 64ch 8 65ch 8 66Other cues•Movement parallax–Nearby objects move faster than distant objectsch 8 67Visual Illusions•http://users.skynet.be/J.Beever/pave.htm•http://www.magiceye.com/ch 8 68Binocular Depth Informationch 8 69Why do we have two eyes?•Long, long time ago, we used to have one eye or no eye at all.•Now we have two eyes.•How come?ch 8 70BeforeI guess we were all like these. NowWe got two eyes. How come?And thench 8 71Something to do with evolution?•Some kind of evolutionary force•Having two eyes is evolutionarily advantageous?•What advantage is it?ch 8 72What eyes are for?–The eye is a sensor.–It is about detecting things in the world.–Eyes used to be part of “skin.”–some part of skin (cell body, membrane) became particularly sensitive to light.–And eventually that part developed to possess eye-like functions.ch 8 73Why are two eyes better than one eye?•Depth perception:•Depth perception is important, because the physical space we live in is three dimensional.•Capturing the three dimensionality of the world is significant for survival, I guess.ch 8 74We got two ears, two nostrils as well.•The same thing is true for ears, and probably for nostrils, too. –But not for the mouth.•Two eyes, two ears, and two nostrils help the organism to locate things in the 3-D worldch