Paper Review #9: Sketch Based Interfaces

1. Paper Bibliography

• Title: Sketch Based Interfaces: Early Processing for Sketch Understanding
• Authors: Tevfik Metin Sezgin, Thomas Stahovich, and Randall Davis
• Publication: ACM SIGGRAPH 2006 Courses. ACM, 2006.

2. Summary

• Target: free sketching
• Target Domain: mechanical engineering design
• Purpose: flexibility & easy to use
• Goal: 
• Converting the original digitized pen strokes in a sketch into the intended geometric objects
• Combining multiple sources of knowledge 

3. Definitions

• A single stroke: from mouse-down to mouse up

4. Details

• Free sketching

• The timing of pen motion can be very informative in regard to free sketching.
• There is no fixed shape to be recognized.

early processing of the basic geometry finding corner + new processing finding line & curve

1. Stroke approximation
: approximate a stroke with more compact and abstract description while minimizing error and avoid overfitting

• Vertex detection
  - Corner of a stroke = high local curvature
  - Combining stroke direction, curvature and speed data
  ex) corner: minimal of speed or maxima of the absolute value of curvature
  1) Average based filtering: Rule out noises(false positives) + variety in angle changes
  - Maxima of curvatures and minima of speed
  - Use thresholds to separate the data into two regions for global extrema
  - Use hybrid fit generation scheme to eliminate false positives
  - The reason why using only curvature data cannot be enough
  
  - The reason why using only speed data cannot be enough
  
  2) Generating hybrid fits
  - Computing vertex certainties
  - Generating a set of hybrid fits
  - Selecting the best fit

• Handling curves: (this is hart part to understand.)

2. Beautification
: make the output visually more appealing without changing its meaning

3. Basic recognition
: interpret the strokes

4. Evaluation

• 13 subjects

5. My opinion

I think this is similar to ShortStraw, but it is much mathematical approach.