L11 - Object Recognition

Question 1

What is object recognition?

Answer 1

• The process of matching a representation of a viewed object to a representation stored in memory.

Question 2

What is recognition by Template Matching?

Answer 2

• Perceived stimuli are compared to templates stored in memory.
• If they match the object is recognised.

Problematic however, when there is variation in stimulus types, changes in viewpoint, illumination.

Question 3

What are the 3 stages of object representations conceptualised by David Marr?

Answer 3

1. Primal sketch:
   - primitive but rich description of the way light information changes across the visual field.
   - captures visual edges and vertices.
2. 2½-D Sketch:
   - recovery of surface information.
   - from the point of the observer (viewer-centred).
   - doesn’t generalise to other viewpoints.
3. 3-D Model representation:
   - recovery of general volumetric parts that make up the object.
   - independent of viewing point (object-centred).

Question 4

What is Irving Biederman’s Recognition by Components Theory?

Answer 4

• All objects are made up of volumetric components (geons).
• 36 geons are sufficient to describe all objects.
• Objects are represented by specific geons and the relations between them.

Question 5

What is the series of steps in Bierderman’s Theory?

Answer 5

Edge extraction (similar to Marr’s primal sketch) -> Parsing regions of concavity OR Detection of non-accidental properties -> Determination of Components (geon decomposition) -> Matching components to object representations.

Question 6

What is the View-Based Theory of Object Recognition?

Answer 6

• Objects are recognised based on stored views that we have encountered through our experience.
• New views must be matched to stored views.
• This requires some form of transformation into alignment.
• “Views” are holistic representations.
• Have difficulty accounting for our ability to categorise new objects as members of a category.