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Sketch based interfaces: early processing for sketch understanding

Paper

Sezgin, Tevfik Metin, Thomas Stahovich, and Randall Davis. "Sketch based interfaces: early processing for sketch understanding." ACM SIGGRAPH 2006 Courses. ACM, 2006.

Publication Link: http://dl.acm.org/citation.cfm?id=

Summary:

In this paper, the authors are using following three phases: approximation, beautification and basic recognition. In Stroke approximation phase, vertex detection is performed first. Vertices can be detected by either speed minima or maxima of curvature. Using only one of them does not provide accurate results and thus we use average based filtering. Extremas in those portions are looked for threshold values(mean in curvature and 90% of mean in speed data). We generate a hybrid fir based on the data. 

Noise and variety in angle changes, both pose a problem on the credibility of a single data. Using only speed, vertices might be missed and just using curvature data, extra vertices may be counted. Hybrid fit is generated by intersection of both points and then point from each is added to see which point leads to lesser OSDQ error value. For curves, ratio of Euclidean distance and arc length is used. The curve is recursively subdivided in the middle. Next steps are beautification and Basic object recognition.

Discussion:

The paper could have discussed more about how the values of threshold are calculated and why the 90% is chosen in case of speed data. The idea of using minimal feature set i.e only two (speed and curvature) is very promising