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Space Perception

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 components Oriented texture can enhance shape perception. Lighting model. Lambertian, specular, ambient + cast shadows.

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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 andMcKenzie) Perspective Picture plane position Occlusion Picture plane position Occlusion

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

  17. Structure from Motion

  18. Cast Shadows

  19. Stereo Vision Basics

  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 , 96 Motion parallax 0.001 Occlusion Height in field 0.01 Relative size Depth Contrast 0.1 Binocular disparity Convergence accommodation 1.0 Aerial 1 10 100 Depth (meters) Cutting, 1996

  23. Task Based Space Perception

  24. 3D options Vergence Focus Motion Parallax Stereopsis Shape-from Shading or Texture Perspective Occlusion

  25. Cue dependencies

  26. Yes of course 3D can give us moreBut 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

  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%

  33. How to generateMotion? • Passive rotation • Hand coupled rotation • Head-coupled rotation • Time has does not vary much

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

  35. Stereo Vision Basics

  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)

  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

  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. 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) Conclusion – 3D is better but only it adds something

  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 Right Eye To Left 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

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