Name: Answer Key
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624 Sketch Recognition Quiz 17 – Answer Key: December 5, 2014
1. In class, we talked about a sliding window method that improves upon the traditional approach of
square, uniformly-sized blocks. Draw the window we talked about as it may be used in a
Computer Vision application.
2. Why would we use this representation rather than a square divided into a uniform grid?
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The important information and objects in images tend to be nearer the center. The
concentric circular sliding window helps focus more on the center and provide more
detail where it is most relevant, as opposed to a square sliding window
3. Draw the sliding window we would be more likely to use in a Sketch Recognition application.
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Rotated by ~22.5 degrees
4. Why the change between the Computer Vision and Sketch Recognition windows?
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The information present in images can be derived from objects, textures, and colors;
edges are not as critical to capture. The horizon itself is less important than what is
on it. Conversely, a sketch only has lines/edges, so the horizon is important in
understanding the sketch and becomes important to capture.
In a related manner, even a little noise/error in drawing a line (with extremely small
positive or negative slope) can put that in different window and result in wrong
answers if the window for computer vision were used. However, a rotated window is
much accommodating with slightly tilted lines and helps in proper recognition.
5. In the World of Workout paper, a variety of real-world exercises are combined into what three
game-level attributes?
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Strength
Speed
Stamina
6. Why did the authors include a fatigue factor in their game?
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To make it safer. They want to promote health activity but at the same time, don’t
want users to repeat it to unhealthy levels
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To prevent users from cheating the system where they are not actually doing the
exercise but are just pretending to walk by moving their feet.
7. Explain briefly (just 2-3 lines) how shape recognition is carried out in ‘Recognizing Interspersed
Sketches Quickly’ paper.
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Recognize domain-independent primitives
Apply constraints and indexes on those primitives
Based on that, identify higher level shapes
8. What are the three stages of the indexing algorithm used in the ‘Recognizing Interspersed
Sketches Quickly’ paper?
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Domain Independent Primitive Finding
Domain Independent Constraint-Indexing
Domain Dependent Shape Recognition
9. What is the motivation behind the KimCHI paper?
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To design better Pen-based User Interfaces for kids
Assess the developmental level of kids’ drawing abilities,
10. In the KimCHI paper, out of the 8 Classifiers used, which two classifiers performed better for
classifying preschoolers vs. grade-schoolers?
- Random Forests
- Bagging