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Visual thinking colin_ware_lectures_2013_7_3_d space perception

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  • 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 Ambient illumination Specular refection diffuse reflection = lambertian
  • 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
  • 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. Occlusion: The strongest depth cue
  • 13. Perspective
  • 14. Perspective
  • 15. Perspective (Cockburn and McKenzie) Perspective Picture plane position Occlusion Picture plane position Occlusion
  • 16. Atmospheric perspective Reduce contrast with distance “depth cueing” in CG
  • 17. Structure from Motion b a c
  • 18. Cast Shadows
  • 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. 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. Frame Cancellation
  • 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. 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. 3D options Shape-from Shading or Texture Vergence Motion Parallax Stereopsis Perspective Occlusion Focus
  • 25. Cue dependencies Vergence Kinetic Depth Linear Perspective Stereo Texture gradients Depth of focus Occlusion
  • 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. 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. Random Graphs
  • 29. Glenn looking at a graph
  • 30. Fish Tank VR
  • 31. The task
  • 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.    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. Stereo Display Requirements     3D GIS data Comfortable stereo display Many orders of magnitude Better than normal stereopsis
  • 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. 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. Cyclopean Scale: (with Cyril Gobrecht) Oia rg l i n S ld ce a
  • 38. Cyclopean Scale Helps with       Vergence focus conflict Diplopia Disparity scaling Frame cancellation It works dynamically? Change the virtual eye separation
  • 39. Virtual Eye Separation
  • 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. Understanding surface shape Victoria Interrante
  • 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. 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. Stereo technologies  Frame-sequential (shutter glasses) Polaroids Mirror stereoscope HMDs Color anaglyphs Chromadepth  Holograms     
  • 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. Polaroids Silver screen Preserves polarization R L Problems: ghosting Advantages: Cheap glasses
  • 47. Anaglyphs Problems: Ghosting Inability to use color
  • 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. Mirror stereoscope Advantages: no ghosting Retains full brightness Full spatiotemporal resolution possible Disadvantage: Fixed head position.
  • 50. HMD stereoscope Different screens for each eye. A high image quality is possible, but not currently available
  • 51. VR    What is it? What is it for? Perception/interaction
  • 52. Issue      Resolution Ghosting Vergence-focus conflict Occlusion Crossed disparities
  • 53. Immersion VR   HMD + head tracking Data glove
  • 54. Fish Tank VR  Head tracking, stereo, touch
  • 55. Desk Top VR  Interactive 3D
  • 56. CAVE      Head tracking – stereo Resolution problems Light scattering problems Vergence focus problem for near object Occlusion problems for near objects
  • 57. Data walls (near immersion)  Stereo, no head tracking, wide screen
  • 58. Immersadesk  Head tracking, stereo
  • 59. Augmented reality (Feiner)     Add text+images to real world See through glasses Very sensitive to head tracking Occlusion problems