Depth Cues

2. Depth Cues • Pictorial Depth Cues: aspects of 2D images that imply depth • Physiological Depth Cues: Proprioception in ocular muscles indicates accommodation and convergence • Motion Depth Cues: foreground and background move in opposite directions • Stereoscopic Depth Cues: disparity between two retinal images indicates distance

3. Pictorial Depth Cues • Texture gradient

4. Pictorial Depth Cues • Height in the plane

5. More Depth Cues • Pictorial Depth Cues • Physiological Depth Cues • Motion Parallax • Stereoscopic Depth Cues

6. Physiological Depth Cues • Two Physiological Depth Cues • accommodation • convergence

7. Physiological Depth Cues • Accommodation

8. Physiological Depth Cues • Convergence

9. Physiological Depth Cues • Convergence • small angle of convergence = far away • large angle of convergence = near • What two sensory systems is the brain integrating? • What happens to images closer or farther away from fixation point?

10. Physiological Depth Cues • Convergence and accommodation are reflexively linked Under what circumstances might this be a problem?

11. Motion Depth Cues • Motion • Parallax

12. Motion Depth Cues • Parallax

13. Motion Depth Cues • Parallax • points at different locations in the visual field move at different speeds depending on their distance from fixation

14. Motion Depth Cues • Parallax

15. Seeing in Stereo Seeing in Stereo

16. Seeing in Stereo It’s very hard to read words if there are multiple images on your retina It’s very hard to read words if there are multiple images on your retina

17. Seeing in Stereo It’s very hard to read words if there are multiple images on your retina It’s very hard to read words if there are multiple images on your retina But how many images are there on your retinae?

18. Binocular Disparity • Your eyes have a different image on each retina • hold pen at arms length and fixate the spot • how many pens do you see? • which pen matches which eye?

19. Binocular Disparity • Your eyes have a different image on each retina • now fixate the pen • how many spots do you see? • which spot matches which eye?

20. Binocular Disparity • Binocular disparity is the difference between the two images

21. Binocular Disparity • Binocular disparity is the difference between the two images • Disparity depends on where the object is relative to the fixation point: • objects closer than fixation project images that “cross” • objects farther than fixation project images that do not “cross”

22. Binocular Disparity • Corresponding retinal points

23. Binocular Disparity • Corresponding retinal points

24. Binocular Disparity • Corresponding retinal points

25. Binocular Disparity • Corresponding retinal points

26. Binocular Disparity • Points in space that have corresponding retinal points define a plane called the horopter The Horopter

27. Binocular Disparity • Points not on the horopter will be disparate on the retina (they project images onto non-corresponding points)

28. Binocular Disparity • Points not on the horopter will be disparate on the retina (they project images onto non-corresponding points) • The nature of the disparity depends on where they are relative to the horopter

29. Binocular Disparity • points nearer than horopter have crossed disparity • points farther than horopter have uncrossed disparity The Horopter

30. Binocular Disparity • Why don’t we see double vision?

31. Binocular Disparity • Why don’t we see double vision? • Images with a small enough disparity are fused into a single image