1. Sensation & Perception
Ch. 10: Perceiving depth and size
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Main topics
Monocular depth cues
Binocular depth cues
Visual illusion
The physiology of depth perception
ch 10

2. Tell me why these pictures look bizarre?
ch 10

3. Escher:
Ascending
ch 10

4. Belvedere: Escher
ch 10

5. Red Ants: Escher
ch 10

6. Relativity: Escher
ch 10

7. Up and Down: Escher
ch 10

8. Waterfall: Escher
ch 10

9. ch 10

10. De Chirico
ch 10

11. Why do these paintings evoke a strange feeling?
ch 10

12. Leonardo da Vinci (1452-1519) Mona Lisa (1503)
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 10

13. The Dreyfus Madonna: da Vinci 1469
ch 10

14. Why did Leonardo become so famous?
One secret:
ch 10

15. The Last Supper: da Vinci, 1498
ch 10

16. The virgin of the rocks: da Vinci, 1483-1486
ch 10

17. Madonna Litta: (da Vinci) 1490-1491
ch 10

18. The Santa Trinita Madonna: Cimabue (1260/80)
ch 10

19. Coronation of the virgin altarpiece from San Domenico: Fra Angelico, 1434
ch 10

20. The presentation of the virgin: Giotto, 1305
ch 10

21. Madonna in Glory: Giotto, 1311
ch 10

22. Why did Leonardo become so famous?
Or what made Leonardo’s pictures so special?
ch 10

23. Historical depiction of Madonna
1260/80
1311
1434
2000
Historical depiction of Madonna
1469
ch 10

24. Historical depiction of Madonna
1260/80
1311
1434
2000
Historical depiction of Madonna
1469
ch 10

25. ch 10

26. What I think: Everything before Leonardo was very flat.
These pictures were so crisp clear.
No ambiguity.
Leonardo (A-rod) made things more ambiguous.
ch 10

27. Leonardo found two tricks
To depict distance, L used (but not W, definitely not A-rod)
Linear perspective
Atmospheric perspective
ch 10

28. Leonardo used lots of pictorial cues to depict depth
ch 10

29. Atmospheric perspective
Things get vague when they are away.
ch 10

30. Things get smaller when they are away.
ch 10

31. Linear perspective
Things get smaller when they are away.
ch 10

32. Linear perspective Linear perspective is very “Renaissance.”
Renaissance  humanism  free from feudalism (religious bigotry)
Put a person at the center of the world.
Not religious authority
ch 10

33. Other quintessential Renaissance men are
Descartes ( )
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 10

34. and arrange everything else based on that center.
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 10

35. Monocular pictorial cues
Occlusion
Relative height
Relative size
Familiar size
Atmospheric perspective
Linear perspective
ch 10

36. Occlusion
ch 10

37. Relative height
ch 10

38. Relative size
ch 10

39. Atmospheric perspective
ch 10

40. ch 10

41. ch 10

42. ch 10

43. Texture gradient
ch 10

44. ch 10

45. 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 10

46. Visual Illusions
ch 10

47. (A)
(B)
(A)
(B)
ch 10

48. ch 10

49. ch 10

50. ch 10

51. ch 10

52. Tell me why these pictures bizarre?
Any idea?
ch 10

53. What makes these pictures surreal?
ch 10

54. What makes these pictures surreal?
ch 10

55. Any idea?
ch 10

56. My guess: These pictures deliberately violate pictorial cues.
 which evokes a strange feeling.
 these pictures depict impossible scenes by reversing depth relations.
ch 10

57. Violating some depth cues
Deliberately introducing contradictory depth information.
ch 10

58. What makes these pictures surreal?
Violating linear perspective
ch 10

59. ch 10

60. ch 10

61. ch 10

62. How to make an Escher figure.

63. ch 10

64. Other cues Movement parallax
Nearby objects move faster than distant objects
ch 10

65. Visual Illusions http://users.skynet.be/J.Beever/pave.htm
Ames room (1:13)
Star wars: Attack of the clones (10 min)
ch 10

66. Binocular Depth Information
ch 10

67. Why 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 10

68. I guess we were all like these.
Now
We got two eyes. How come?
Before
I guess we were all like these.
And then
ch 10

69. Something to do with evolution?
Some kind of evolutionary force
Having two eyes is evolutionarily advantageous?
What advantage is it?
ch 10

70. What 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 10

71. We 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 world
ch 10

72. Binocular depth cues Ever visited an IMAX theater?
Or some special planetarium?
Wearing special sunglasses and see a large screen.
You get an incredible 3-D effect.
ch 10

73. ch 10

74. Binocular disparity & Binocular depth cues
ch 10

75. Demo
Step 1: Hold your one finger about 8 inches in front of you and the other about 15 inches in front of you.
Step 2: Focus on the one that is further from you, and move the other finger back and forth.
Got double images for the unfocused finger? But why?
ch 10

76. Binocular disparity
Your two eyes are getting different images  disparity  double images
Corresponding points
Corresponding points
No disparity
disparity
ch 10

77. Small disparity
Large disparity
No disparity
ch 10

78. Horopter (Vieth-Muller circle)
ch 10

79. Binocular disparity
The binocular disparity arises when a given point in the external world does not project to the corresponding points on the left and right retinae
(Palmer, 1999, “Vision Science”)
ch 10

80. Binocular disparity
- OK, then open your right eye and close your left eye. What happens? Repeat this several times.
ch 10

81. Binocular disparity
- OK, then open your right eye and close your left eye. What happens? Repeat this several times.
ch 10

82. Do the same thing several times.
This time change the distance between your focused and unfocused fingers.
When your unfocused finger is close to you,
That finger moves further left.
ch 10

83. Your unfocused finger moves to the left. Why?
ch 10

84. small
distance
large
distance
Small disparity
large disparity
ch 10

85. Binocular disparity
The amount of disparity can tell us how far an object is apart from the object you are focusing on.
But how do we know the unfocused objects is farther from or closer to you?
ch 10

86. 2 types of disparity crossed disparity uncrossed disparity F P P C
ch 10

87. Both F and C do not fall on the corresponding points.
P falls on the foveae of both eyes, so they stimulate corresponding points.
Both F and C do not fall on the corresponding points.
C is close, and the disparity goes outward.
 “Crossed disparity”
F is farther, and the disparity goes inward.
 “uncrossed disparity”
These two types of disparity signals the brain whether the object is close to or far from you.
ch 10

88. Where? Binocular depth cue  you need two eyes
V1 (striate cortex is the first location where the information from the two eyes is merged).
Specific neurons in V1, V2 and V3 respond to disparity.
ch 10

89. Emmert’s law S = R x D S: Perceived size R: retinal image
D: perceived distance
ch 10

90. Figure 10.33
The principle behind the observation that the size of an afterimage increases as the afterimage is viewed against more distant surfaces.
ch 10
Fig , p. 248