Sezgin2007Sketch - Sketch-Based Interaction Sketch...

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Sketch-Based Interaction 28 January/February 2007 Published by the IEEE Computer Society 0272-1716/07/$20.00 © 2007 IEEE S ketching is a natural input modality that has received increased interest in the com- puter graphics and human–computer interaction com- munities. The emergence of hardware such as tablet PCs and handheld PDAs provides easy means for cap- turing pen input. These devices combine a display, pen tracker, and computing device, making it possible to capture and process sketches online, as they are drawn. Online recognition has two main advantages. First, it enables interpreting and displaying pen input as it is entered—for example, an engineer drawing a circuit diagram receives system feedback by observing the ink changing color in real time, indi- cating which circuit components are recognized. Second, an online sketching system provides access to stroke-ordering information as well as the end product of the drawing process. When we refer to temporal patterns in this article, we mean this stroke-ordering information. In certain domains, temporal stroke orderings used when sketch- ing objects contain predictable pat- terns that a system can use for object recognition. 1 We call these stroke- level patterns because they capture the probability of seeing a sequence of strokes with certain properties. For example, when people draw stick ±gures, one frequent- ly seen stroke-level pattern is a sequence of a circular stroke, a vertical line, and two pairs of positively and negatively sloped lines, corresponding to the figure’s head, body, arms, and legs. Another temporal pattern in online sketches is an object-level pattern, which captures the probability of seeing a certain sequence of objects being drawn. Con- sider the domain of Uni±ed Modeling Language class diagrams, drawn by software designers using rectan- gles to indicate classes and various arrows to indicate relations among classes, such as inheritance, general- ization, and association. In this domain, when a design- er draws a new class (indicated by a rectangle), it’s natural to expect that the new object will soon be con- nected with an arrow to one or more of the objects drawn earlier. We describe this as an object-level pat- tern, indicating that drawing a class is followed by draw- ing some variety of arrow. The kind of arrow to expect can depend on the kind of class drawn. A ±nal class, for example, can’t be extended, which limits the kind of arrow that we can expect next. In domains like the Unified Modeling Language, which has a graphical grammar of sorts, it’s plausible to imagine writing down the grammar and using this to guide a UML-diagram recognition system. But few domains have patterns that are as well understood as those for UML diagrams. And even if experts could iden- tify such patterns, incorporating them into a recogni- tion system would be a laborious task at best, considering all the ways that various objects can com- bine. A better way of incorporating object-level tempo- ral patterns in a recognition framework would be to learn them, along with stroke-level patterns, from data.
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This note was uploaded on 06/12/2011 for the course CAP 6105 taught by Professor Lavoila during the Spring '09 term at University of Central Florida.

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Sezgin2007Sketch - Sketch-Based Interaction Sketch...

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