Space Perception




Depth Cues
Tasks
Shape-from-Shading
Perception of surface shape






Simple lighting model
Light from above and at infinity
Specular, Diffuse and Ambient...
Lighting model

Lambertian, specular, ambient + cast shadows
Standard lighting model
Ambient illumination
Specular refection
diffuse reflection =
lambertian
Examples
Shading

Specular reveals fine detail
Cushion Tree Map Jarke Van
Wijk
Contour and Shading
Textures for surface orientation
(Interrante)
Lighting







Simple lighting model
Not photorealistic
Single light source from above and at
infinity
Specular for ...
The 3D vs 2D debate






Should we display abstract data in 3D?
Depth cue theory
Depth cues are environmental informa...
Occlusion: The strongest depth
cue
Perspective
Perspective
Perspective (Cockburn and McKenzie)

Perspective
Picture plane position
Occlusion

Picture plane position
Occlusion
Atmospheric perspective

Reduce contrast with distance
“depth cueing” in CG
Structure from Motion

b
a

c
Cast Shadows
Stereo Vision Basics
P n m F s n lAe
a u 's uio a r a
Sr e
ce n
R h ee
ig t y

d p rty=α-β
is ai
α
Lf e e
et y

β
Stereopsis






Based on disparities
A super acuity
Only good near point of fixation
Poor for large differences
Doub...
Frame Cancellation
Relative Importance

Depth Contrast

0.001

Motion
parallax

Occlusion
Height in field

0.01

Relative size

, 96

0.1

Bi...
Task Based Space Perception
C
1

C1

C
2

C2

C
3
C
4

C
N

3 C g itiv
D on e
Md l
oe
o Ev n e t
f n iro mn

C3
TskP n in
...
3D options

Shape-from
Shading or
Texture

Vergence

Motion
Parallax

Stereopsis

Perspective
Occlusion

Focus
Cue dependencies
Vergence

Kinetic Depth

Linear Perspective

Stereo

Texture gradients
Depth of focus

Occlusion
Yes of course 3D can give us
more
But only if it supports some task


Locomotion




Understanding the shape of surface...
Relative position




For fine judgments - threading a needle
stereo is important +shadows, occlusion
For large scale ju...
Random Graphs
Glenn looking at a graph
Fish Tank VR
The task
Stereo +60%
Motion +130%
Stereo +
Motion
+200%

Stereo head coupled perspective
2D
Stereo head coupled perspective

2D
Ste...






Passive rotation
Hand coupled rotation
Head-coupled
rotation

Time has does not
vary much
Perspective
Stereo
Pass...
Stereo Display Requirements





3D GIS data
Comfortable stereo display
Many orders of magnitude
Better than normal st...
Stereo Vision Basics
P n m F s n lAe
a u 's uio a r a
Sr e
ce n
R h ee
ig t y

d p rty=α-β
is ai
α
Lf e e
et y

β
We Know That







Vergence and focus conflict
Stereo perception is plastic (Wallack)
Can be rapidly recalibrated (J...
Cyclopean Scale: (with Cyril
Gobrecht)
Oia
rg l
i n
S ld
ce
a
Cyclopean Scale Helps with







Vergence focus conflict
Diplopia
Disparity scaling
Frame cancellation
It works dyn...
Virtual Eye
Separation
Change in Eye Separation with
Depth
2
4
2
2
2
0
1
8
1
6
1
4
1
2
1
0
8
6
4

1
0

2
0

3
0

4
0

5
0

6
0

A g o m v gp tte ...
Understanding surface shape

Victoria Interrante
Norman, Todd & Phillips

Note: Random textures on surfaces
Stereo and motion roughly equal
Note large angular error ~ 20 d...
Conclusion – 3D is better but only
it adds something






Space perception
depends on the task
Occlusion the most
impo...
Stereo technologies



Frame-sequential (shutter glasses)
Polaroids
Mirror stereoscope
HMDs
Color anaglyphs
Chromadepth

...
Stereo shutter glasses
Alternate right and left eye images on monitor.
Syncronized shutters block right and left eyes in
a...
Polaroids

Silver screen
Preserves polarization

R
L
Problems:
ghosting

Advantages: Cheap glasses
Anaglyphs

Problems:
Ghosting
Inability to use color
Works with LCD displays

Lenticular

To Left Eye

To Right Eye

The display uses cylindrical
Prisms in vertical columns

W...
Mirror stereoscope

Advantages: no ghosting
Retains full brightness
Full spatiotemporal resolution possible
Disadvantage: ...
HMD stereoscope

Different screens for each eye.
A high image quality is possible, but not currently available
VR




What is it?
What is it for?
Perception/interaction
Issue






Resolution
Ghosting
Vergence-focus conflict
Occlusion
Crossed disparities
Immersion VR



HMD + head tracking
Data glove
Fish Tank VR


Head tracking, stereo, touch
Desk Top VR


Interactive 3D
CAVE






Head tracking – stereo
Resolution problems
Light scattering problems
Vergence focus problem for near objec...
Data walls (near immersion)


Stereo, no head tracking, wide screen
Immersadesk


Head tracking, stereo
Augmented reality (Feiner)





Add text+images to real world
See through glasses
Very sensitive to head tracking
Occl...
Visual thinking colin_ware_lectures_2013_7_3_d space perception
Visual thinking colin_ware_lectures_2013_7_3_d space perception
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Visual thinking colin_ware_lectures_2013_7_3_d space perception

  1. 1. Space Perception    Depth Cues Tasks Shape-from-Shading
  2. 2. Perception of surface shape     Simple lighting model Light from above and at infinity Specular, Diffuse and Ambient components Oriented texture can enhance shape perception
  3. 3. Lighting model Lambertian, specular, ambient + cast shadows
  4. 4. Standard lighting model Ambient illumination Specular refection diffuse reflection = lambertian
  5. 5. Examples
  6. 6. Shading Specular reveals fine detail
  7. 7. Cushion Tree Map Jarke Van Wijk
  8. 8. Contour and Shading
  9. 9. Textures for surface orientation (Interrante)
  10. 10. Lighting      Simple lighting model Not photorealistic Single light source from above and at infinity Specular for detail Cast shadows if scene is simple
  11. 11. The 3D vs 2D debate     Should we display abstract data in 3D? Depth cue theory Depth cues are environmental information that tell us about space Can be applied somewhat independently
  12. 12. Occlusion: The strongest depth cue
  13. 13. Perspective
  14. 14. Perspective
  15. 15. Perspective (Cockburn and McKenzie) Perspective Picture plane position Occlusion Picture plane position Occlusion
  16. 16. Atmospheric perspective Reduce contrast with distance “depth cueing” in CG
  17. 17. Structure from Motion b a c
  18. 18. Cast Shadows
  19. 19. Stereo Vision Basics P n m F s n lAe a u 's uio a r a Sr e ce n R h ee ig t y d p rty=α-β is ai α Lf e e et y β
  20. 20. Stereopsis      Based on disparities A super acuity Only good near point of fixation Poor for large differences Double imaging possible for 1/10th deg.
  21. 21. Frame Cancellation
  22. 22. Relative Importance Depth Contrast 0.001 Motion parallax Occlusion Height in field 0.01 Relative size , 96 0.1 Binocular disparity Convergence accommodation 1.0 1 Aerial 10 Depth (meters) 100 Cutting, 1996
  23. 23. Task Based Space Perception C 1 C1 C 2 C2 C 3 C 4 C N 3 C g itiv D on e Md l oe o Ev n e t f n iro mn C3 TskP n in a la n g a dE e u n n x c tio C4 CN Task Planning and Execution
  24. 24. 3D options Shape-from Shading or Texture Vergence Motion Parallax Stereopsis Perspective Occlusion Focus
  25. 25. Cue dependencies Vergence Kinetic Depth Linear Perspective Stereo Texture gradients Depth of focus Occlusion
  26. 26. Yes of course 3D can give us more But only if it supports some task  Locomotion   Understanding the shape of surfaces   Shading, texture, stereo, motion Tracing paths in graphs   Heading, occlusion motion stereo Local reaching  stereo – convergence
  27. 27. Relative position   For fine judgments - threading a needle stereo is important +shadows, occlusion For large scale judgments, perspective, motion parallax, linear perspective are all important. Stereo is not important
  28. 28. Random Graphs
  29. 29. Glenn looking at a graph
  30. 30. Fish Tank VR
  31. 31. The task
  32. 32. Stereo +60% Motion +130% Stereo + Motion +200% Stereo head coupled perspective 2D Stereo head coupled perspective 2D Stereo perspective Head coupled perspective 50 40 30 20 10 0 0 50 1 00 15 0 2 00 Number of Nodes 250 30 0
  33. 33.    Passive rotation Hand coupled rotation Head-coupled rotation Time has does not vary much Perspective Stereo Passive rotation Stereo passive Hand coupled Stereo hand Head coupled Perspective Stereo Passive rotation Stereo passive Hand coupled Stereo hand Head coupled Stereo head 2D 12 10 8 6 4 2 0 2D 0 Stereo head  Time (sec) Errors (%) How to generate Motion? 30 20 10
  34. 34. Stereo Display Requirements     3D GIS data Comfortable stereo display Many orders of magnitude Better than normal stereopsis
  35. 35. Stereo Vision Basics P n m F s n lAe a u 's uio a r a Sr e ce n R h ee ig t y d p rty=α-β is ai α Lf e e et y β
  36. 36. We Know That      Vergence and focus conflict Stereo perception is plastic (Wallack) Can be rapidly recalibrated (Judge and Miles) There is a synergy with motion parallax Occlusion is a strong cue to depth
  37. 37. Cyclopean Scale: (with Cyril Gobrecht) Oia rg l i n S ld ce a
  38. 38. Cyclopean Scale Helps with       Vergence focus conflict Diplopia Disparity scaling Frame cancellation It works dynamically? Change the virtual eye separation
  39. 39. Virtual Eye Separation
  40. 40. Change in Eye Separation with Depth 2 4 2 2 2 0 1 8 1 6 1 4 1 2 1 0 8 6 4 1 0 2 0 3 0 4 0 5 0 6 0 A g o m v gp tte (d g n le f o in a rn e ) 7 0 8 0
  41. 41. Understanding surface shape Victoria Interrante
  42. 42. Norman, Todd & Phillips Note: Random textures on surfaces Stereo and motion roughly equal Note large angular error ~ 20 degrees Observation: Stereopsis is a super-acuity and relies on fine texture disparity gradients
  43. 43. Conclusion – 3D is better but only it adds something    Space perception depends on the task Occlusion the most important depth cue – consider that windows rely on it Perspective may not add anything by itself    Stereo important for close interaction Motion important for 3D layout Shape-from shading and texture important for surface perception (but non photorealist)
  44. 44. Stereo technologies  Frame-sequential (shutter glasses) Polaroids Mirror stereoscope HMDs Color anaglyphs Chromadepth  Holograms     
  45. 45. Stereo shutter glasses Alternate right and left eye images on monitor. Syncronized shutters block right and left eyes in alternation Monitor: 120 Hz R,L eyes 60 Hz each Problems: ghosting due to slow Phosphor decay. Lower resolution CRT displays only Expensive glasses
  46. 46. Polaroids Silver screen Preserves polarization R L Problems: ghosting Advantages: Cheap glasses
  47. 47. Anaglyphs Problems: Ghosting Inability to use color
  48. 48. Works with LCD displays Lenticular To Left Eye To Right Eye The display uses cylindrical Prisms in vertical columns What is wrong with this picture? Problems: reduced resolution, limited head position. Theoretical limits on resolution
  49. 49. Mirror stereoscope Advantages: no ghosting Retains full brightness Full spatiotemporal resolution possible Disadvantage: Fixed head position.
  50. 50. HMD stereoscope Different screens for each eye. A high image quality is possible, but not currently available
  51. 51. VR    What is it? What is it for? Perception/interaction
  52. 52. Issue      Resolution Ghosting Vergence-focus conflict Occlusion Crossed disparities
  53. 53. Immersion VR   HMD + head tracking Data glove
  54. 54. Fish Tank VR  Head tracking, stereo, touch
  55. 55. Desk Top VR  Interactive 3D
  56. 56. CAVE      Head tracking – stereo Resolution problems Light scattering problems Vergence focus problem for near object Occlusion problems for near objects
  57. 57. Data walls (near immersion)  Stereo, no head tracking, wide screen
  58. 58. Immersadesk  Head tracking, stereo
  59. 59. Augmented reality (Feiner)     Add text+images to real world See through glasses Very sensitive to head tracking Occlusion problems

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