wk 5 SP

Question 1

Two approaches to perception of form and organisation

Answer 1

Marr’s approach, concerned with contrast change

Gestalt approach, concerned with rules of perceptual organisation

Question 2

Marr’s approach to perception of form and organisation (process)

Answer 2

Retinal image is analysed sequentially at different levels:

Retinal image –> Grey level description ( measure intensity of light at each point)
—> Primal sketch (representation of contrast change e.g. blobs, edges, bars etc)
–> 2 1/2 D sketch ( representation of orientation, depth, colour ,relative to observer,) Its not 3D because it is observer-orientated. (unseen parts of scene
and objects)
—> 3D representation- representations of objects independent to observer

Question 3

Gestalt laws of perceptual
organisation

Answer 3

1. similarity
2. Good continuation (lines follow smoothest path)
3. Proximity (close = grouped)
4. Connectedness (physically connected = unit)
5. Closure (e.g 4 on a dice looks like a square)
6. Common fate (moving together in same direction = grouped)
7. Familiarity ( once discovered one indicator of object, don’t need all)
8. Invariance (recognise under diff visual situations)
9. Pragnanz- “good figure” (central law- most simple + stable shape)

Question 4

Figure-ground segregation- properties effecting whether area is seen as figure or ground are:

(background or foreground)

Answer 4

• symetry (symetry usually figure)
  -Convexity (convex usually figure)
  -Area (smaller area usually figure)
  -Orientation (vertical + horizontal usually figure
  -Meaning/importance. this implies top-down processiing occurs here

Question 5

maybe do more on bottom up and top down