Reading #9. PaleoSketch: Accurate Primitive Sketch Recognition and Beautification (Paulson)

COMMENTS:

Drew-Drew

SUMMARY:

This paper discusses PaleoSketch, a low-level sketch recognition system that recognizes primitive shapes such as lines, polylines, arcs and curves.  PaleoSketch does pre-recognition by resampling and removing duplicate points.  In addition to the usual stroke features (stroke direction, speed, curvature, etc.) the authors introduce two additional features: normalized distance between direction extremes which is the stroke length between the point with the highest direction value and the point with the lowest direction value, and the direction change ratio which is the maximum change in direction divided by the average change in direction. 

PaleoSketch assigns a set of conditions to each primitive and determines which shape is the best fit.  The authors go on to describe the conditions of each primitive shape.  PaleoSketch has an accuracy rate of 98.56%.

DISCUSSION:

I think the first programming assignment is a great introduction to PaleoSketch and the sketch recognition problem.  Before I read this paper, I had kind of a fuzzy understanding of what strokes represent primitive strokes.  While I think this is still somewhat arguable, I believe the authors have chosen a good set of primitives to recognize.  So far, I have not seen a more complicated primitive in the data that was provided for the assignment. 

Using the TestApplication, you can see how the recognizer determines a line is a polyline, but apparently this condition is easy to fool.  I don’t believe the system can recognize polylines consistently if the change in direction is minimal.  Perhaps in this case speed should be carefully weighed.