1. Topic 14: Jacob O. Wobbrock, Andrew D. Wilson, and Yang Li. 2007
Topic 14: Jacob O. Wobbrock, Andrew D. Wilson, and Yang Li Gestures without libraries, toolkits or training: a $1 recognizer for user interface prototypes. In Proceedings of the 20th annual ACM symposium on User interface software and technology (UIST '07). ACM, New York, NY, USA,
Presented by Brad Myers
05-773A4: Computer Science Perspectives in HCI, (CS Mini), Spring, 2017
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2. Notes Please fill out the course anonymous questionnaires:
mine: 
official CMU:
Literature review due next Tuesday, electronic only, on Blackboard
Submission site is already open, if you want to be early 
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3. Authors Jake Wobbrock – PhD at CMU with Brad, now Prof. at Univ. Wash
Andy Wilson – Microsoft Research, original surface, Kinect, displays, etc.
Yang Li – researcher at Google in Seattle on gesture recognition
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4. Motivation Rubine’s algorithm’s problems
Inaccuracy, inefficiency, hard to understand
Complexity
Wanted a simple algorithm with no complex math
Run in real-time (no lag)
Train with only 1 example (instead of 15 like Rubine)
Still focused on single-stroke, one finger gestures
Note: 2007 = before the iPhone and its gestures became popular
Later research by the authors and others extended it to work with multi-stroke, multi-finger, and 3D gestures
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5. Target gesture set
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6. Detailed Algorithm In the paper, but generally:
Make the user’s gesture have a fixed number of points evenly spaced
Make the user’s gesture have a standard size (fit to a square) and orientation
Compare to a set of candidate templates
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7. Evaluation 10 subjects did the 16 gestures in Figure 1
3 sets of 10 entries for each at slow, medium, and fast speeds
10*16*30 = 4800 total entries
$1 significantly more accurate than Rubine and faster than both Rubine and the DTW algorithm
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8. Discussion questions
Besides flicking and squeezing, are there any other gestures that are commonplace?
Have you ever used a system that recognizes gestures like those shown in Figure 1? For what?
There are commercial drawing programs for tablets that recognize gestures to make rectangles, lines, circles, arrows, etc. Do these work better than using a conventional palette to pick tools?
Given that the algorithm is "rotation, scale, and position invariant" and ignores timing, are there any important kinds of gestures that this algorithm won't recognize?
 Given how long gesture recognizers have been studied, why aren't they more commonly used?
© Brad Myers