1. Space Perception: the towards- away direction The third dimension Depth Cues Tasks Navigation Cost of Knowledge Interaction

2. Lets think about space as a cost of knowledge.

3. The perception for action pathway

4. 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

5. Do these make any sense?

7. Depth Cues Shape from Shading - texture Occlusion Perspective Shadows Stereo Motion parallax

8. Perception of surface shape Simple lighting model Light from above and at infinity Specular, Diffuse and Ambient components Oriented texture can enhance shape perception

9. Lighting model Lambertian, specular, ambient + cast shadows

10. Standard lighting model Specular refection diffuse reflection = lambertian Ambient illumination

11. Examples

12. Shading Specular reveals fine detail

13. Cushion Tree Map Jarke Van Wijk

14. Lighting Simple lighting model Not photorealistic Single light source from above and at infinity Specular for detail Cast shadows if scene is simple

15. Contour and Shading

16. Textures for surface orientation (Interrante)

17. Understanding surface shape Victoria Interrante

18. Occlusion: The strongest depth cue

19. Perspective

22. Perspective (Cockburn and McKenzie) Perspective Picture plane position Occlusion Picture plane position Occlusion

23. Atmospheric perspective Reduce contrast with distance “depth cueing” in CG

25. Structure from Motion

26. Cast Shadows

27. Stereo Vision Basics

28. Stereopsis Based on disparities A super acuity Only good near point of fixation Poor for large differences Double imaging possible for 1/10 th deg.

29. Frame Cancellation

30. Relative Importance, 96 Cutting, 1996 Depth Contrast Depth (meters) Occlusion 0.001 0.01 0.1 1.0 110100 Relative size Height in field Binocular disparity Motion parallax Convergence accommodation Aerial

31. Task Based Space Perception The important cues depend on the task

32. Cue dependencies

33. Yes of course 3D can give us more But only if it supports some task Locomotion Heading, occlusion, pathways Understanding the shape of surfaces Shading, texture, stereo, motion Tracing paths in graphs motion stereo (not shading, not motion) Local reaching stereo – convergence – sometimes cast shadows

34. 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

36. Random Graphs

37. Glenn looking at a graph

38. Fish Tank VR

39. The task

40. Stereo +60% Motion +130% Stereo + Motion +200%

41. How to generate Motion? Passive rotation Hand coupled rotation Head-coupled rotation Time has does not vary much

42. Surface shape perception (Norman Todd and 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 L=lighting S=specular T = texture

44. Graham Sweet.

45. Stereo Display Requirements 3D GIS data Comfortable stereo display Many orders of magnitude Better than normal stereopsis

46. Stereo Vision Basics

47. 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

48. Cyclopean Scale: (with Cyril Gobrecht)

49. Cyclopean Scale Helps with Vergence focus conflict Diplopia Disparity scaling Frame cancellation It works dynamically? Change the virtual eye separation

50. Virtual Eye Separation

51. 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)

52. Stereo technologies Frame-sequential (shutter glasses) Polaroids Mirror stereoscope HMDs Color anaglyphs Chromadepth Holograms

53. 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

54. Polaroids R L Silver screen Preserves polarization Problems: ghosting Advantages: Cheap glasses

55. Anaglyphs Problems: Ghosting Inability to use color

56. Lenticular To Right Eye To Left Eye The display uses cylindrical Prisms in vertical columns Problems: reduced resolution, limited head position. Theoretical limits on resolution What is wrong with this picture? Works with LCD displays

57. Mirror stereoscope Advantages: no ghosting Retains full brightness Full spatiotemporal resolution possible Disadvantage: Fixed head position.

58. HMD stereoscope Different screens for each eye. A high image quality is possible, but not currently available

59. VR What is it? What is it for? Perception/interaction

60. Issue Resolution Ghosting Vergence-focus conflict Occlusion Crossed disparities

61. Immersion VR HMD + head tracking Data glove

62. Fish Tank VR Head tracking, stereo, touch

63. Desk Top VR Interactive 3D

64. CAVE Head tracking – stereo Resolution problems Light scattering problems Vergence focus problem for near object Occlusion problems for near objects

65. Data walls (near immersion) Stereo, no head tracking, wide screen

66. Immersadesk Head tracking, stereo

67. Augmented reality (Feiner) Add text+images to real world See through glasses Very sensitive to head tracking Occlusion problems