Reading #7

Comments:
Sampath Jayarathna


Summary:

This paper discuss a sketch user interface, by which user can draw naturally as using a pen and paper. And the system is able to recognize the geometric model of the object that user intended to draw. And also this drawing is unrestricted -- it can be in any order or any number of strokes etc.


The algorithm can be described generally in three steps.

Approximation: This process mainly deals with how to detect vertices. For the stroke with a lot of straight line segments, vertices are selected according to the speed of drawing and the curvature at corners. For curves, a Bezier curve is used to approximate/interpolate the shape.

Beautification: Make the drawing more like user’s intention. Make line straight, or paralleled, this may or may not need to move the vertices.

Recognition: Actually, it is just some simple geometric models; a simple template matching is applied.


Finally, the author asked several candidates to try the system, and they all give positive replay.



Discussion:

The most important part of the system is the approximation part, in other word, to extract vertices from the input stroke, if this part can be solved perfectly, the following beautification and recognition part will be much easier to do.

However, how to extract the vertices remains a problem for years, even in this paper. Even in this paper, although the author claimed the accuracy to be 96%, it is based on only 10 figures. The vertices, should also be considered as some kind of features, however, the ways of finding these vertices does not seem convincing to me. (It does not deal with rotation scaling like conventional method does) I am wondering how it will work if comes with some complex examples.