Reading Assignment: Sketch Based Interfaces: Early Processing for Sketch Understanding

Reference Information
Title: Sketch Based Interfaces: Early Processing for Sketch Understanding
Authors: Tevfik Metin Sezgin, Thomas Stahovich, Randall Davis
Citation: "Sketch Based Interfaces: Early Processing for Sketch Understanding", Tevfik Metin Sezgin, Thomas Stahovich, Randall Davis, PUI, 2001.

Summary
This paper discussed a system that was implemented for processing freehand sketching in an attempt to provide a method for natural interactions with a user interface. The interpretation of the freehand gestures into geometric descriptions was discussed, for a representation that can be used by the system easier. However, the interpretation part that was discussed within this paper is intended to be only the first part of a larger system that can provide understanding and interaction using freehand sketching.

Freehand sketching is more complicated than working off of a set of predefined shapes, since anything can be sketched but it still must be able to recognized by the system. Therefore, preprocessing is used in order to distinguish corners from curves to recognize the low-level geometric properties of the gesture. The processing stage includes three phases: approximation, beautification, and basic recognition. Approximation includes finding the vertices at the corners of the gesture by using a hybrid fit with both the stroke information and the timing information associated with sketching the gesture. It also consists of determining the curved sections of the gesture. The approximated data is then used within the beautification phase to improve the appearance of the gesture. The beautified data is used in the basic recognition phase to recognize basic geometric properties from the data.

The system was evaluated using a user study in which participants sketched a set of gestures using the system. Results from the evaluation labeled the system as easy and natural to use due to the ability to draw freehand gestures. In addition, it was determined that the system could efficiently and correctly interpret the freehand shapes that were drawn.

Thoughts
The intention of providing a system for allowing users to apply freehand sketching within user interfaces is an appealing idea. Something like this would open up a number of different interactions with user interfaces that have never been possible before. Since this paper simply described a single part in the process of creating such a system, it would be interesting to find out more about other parts of the system.

One of the most notable findings mentioned within this paper is the fact that timing data can be used to interpret gestures. In particular, it was explained that a user slows down when drawing corners in gestures, allowing corners to be recognized by timing data. One distracting thing that I noticed throughout the paper was that the usage of bounds and thresholds was mentioned multiple times but not how the values of those bounds and thresholds were actually determined. Nevertheless, the contributions of this paper regarding the recognition of freehand sketches seem to have been very important to the field of sketch recognition.