Space Perception: the towards-away direction

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 costof 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 Ambient illumination Specular refection diffuse reflection = lambertian

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

20. Perspective

22. Perspective (Cockburn andMcKenzie) Perspective Picture plane position Occlusion Picture plane position Occlusion

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

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 1/10th deg.

29. Frame Cancellation

30. 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

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

32. Cue dependencies

33. Yes of course 3D can give us moreBut 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 generateMotion? • 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