Lecture on Perception and Depth Perception

Introduction to Depth Perception

• Depth perception: the ability to perceive the world in three dimensions.
• Humans rely on two types of cues for depth perception:
  • Monocular Depth Cues: Cues that require only one eye.
  • Binocular Depth Cues: Cues that require both eyes.

Monocular Depth Cues

1. Relative Size

   • More distant objects appear smaller than closer objects.
   • Example: Cars on a highway.

2. Texture Gradient

   • Object textures are clearer up close and less distinct further away.
   • Example: Flowers and grass appear detailed close up, but textures blend farther away.

3. Interposition (Occlusion)

   • If Object A blocks Object B, Object A is closer.
   • Example: Simple scene with a blue moon, green rectangle, and red star.

4. Linear Perspective

   • Parallel lines appear to converge with distance.
   • Example: Railroad tracks seem to meet at a vanishing point.

5. Height In Plane

   • Distant objects appear higher in the visual field than closer ones.
   • Example: A tree appears higher than a nearby pole.

6. Light and Shadow

   • Shadows reveal information about the three-dimensional shape and depth of objects.
   • Example: Scene illustrating light and shadow.

Binocular Depth Cues

1. Binocular Disparity

   • Each eye sees a slightly different image; the brain combines them.
   • Larger disparities indicate closer objects.
   • Example: Thumbs-up demonstration shows thumb 'jumping' more when closer.

2. Convergence

   • The eyes angle inward to focus on close objects, causing a feeling of eye pressure.
   • Greater convergence means the object is closer.
   • Example: Bringing thumb closer creates convergence and noticeable eye pressure.

Conclusion

• Depth cues are processed automatically by our brains from a young age.
• Both monocular and binocular cues are used together to perceive depth effectively.
• Understanding these cues highlights the complexity and efficiency of human perception.