1. Space Perception Depth Cues Tasks Shape-from-Shading

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. Lighting model Lambertian, specular, ambient + cast shadows

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

5. Examples

6. Shading Specular reveals fine detail

7. Cushion Tree Map Jarke Van Wijk

8. Contour and Shading

9. Textures for surface orientation (Interrante)

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

12. 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

13. Occlusion: The strongest depth cue

14. Perspective

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

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

18. Structure from Motion

19. Cast Shadows

20. Stereo Vision Basics

21. 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.

22. Frame Cancellation

23. 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

24. Task Based Space Perception

25. 3D options Perspective Shape-from Shading or Texture Occlusion Motion Parallax Vergence Focus Stereopsis

26. Cue dependencies

27. Yes of course 3D can give us more But only if it supports some task Locomotion Heading, occlusion Understanding the shape of surfaces Shading, texture, stereo, motion Tracing paths in graphs motion stereo Local reaching stereo – convergence

28. 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

30. Random Graphs

31. Glenn looking at a graph

32. Fish Tank VR

33. The task

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

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

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

37. Stereo Vision Basics

38. 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

39. Cyclopean Scale: (with Cyril Gobrecht)

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

41. Virtual Eye Separation

42. Change in Eye Separation with Depth

43. Understanding surface shape Victoria Interrante

44. 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

45. 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)

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

47. 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

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

49. Anaglyphs Problems: Ghosting Inability to use color

50. 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

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

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

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

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

55. Immersion VR HMD + head tracking Data glove

56. Fish Tank VR Head tracking, stereo, touch

57. Desk Top VR Interactive 3D

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

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

60. Immersadesk Head tracking, stereo

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