Graphical Input through Machine Recognition of Sketches

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Manoj's blog

Summary

In this paper the author first tries to answer the question “Could a machine makes useful interpretations of a sketch without employing knowledge of the subject domain?” He tries to answer this question by means of a system called “HUNCH”. HUNCH is a set of FORTRAN programs and has several components. One part of the program is called STRAIT which found corners in a sketch as function of speed. Curves are considered as a special case of corners. When the curvature of the corner is too gradual or the curve is drawn too carefully the output of the straightening program would go through the curve-fitting program. CURVIT would make one or more passes over the raw data at places pointed out by STRAIT. It was seen that when the output of the STRAIT and CURVIT was shown to the participants; the interpretations made by these programs were not always what the participants expected.

Latching is the idea of joining two or more lines if the sketcher was not able to join them. This also suffered from problems if the domain knowledge was not available. Like in 3D shapes and pictures with varying scales.

Overtracing is idea of replacing several close line with one line by inferring what the user had intended to draw. This also suffered from problems same as of latching for 3D pictures.

The question posed earlier by the author “That is there a syntax of sketching independent of the semantics?” - Is still unresolved. It’s evident from the above scenarios that sketch recognition involves drawing of a sketch and also the context explaining the domain the sketch belongs.

Towards an interactive system: The author here explains an interactive system of sketching where the user can draw in a unobtrusive manner. The system maintains the user inputs and its interpretation in the form of a database. The HUNCH components than can use the database. The HUNCH has three kinds of components. 1) Inference programs: which are improved versions STRAIN, LATCH, OVERTRACE and GUESS. 2) Display programs: which allow displaying any levels of database. 3) Manipulation programs: which allow the user to modify the database directly. In order for the system to be interactive STRAIN works in real time and finds lines and curves on the fly.

In conclusion the author says that the sketch recognition problem has come in a full circle from a insistence on machine recognition with no demands on the user, through knowledge-based systems, and back to more modest interactive approach.

Discussion

The author brings up the idea and complexities involved in sketch recognition and beautification techniques. The author is very right to say that sketch recognition is not possible without the knowledge of context in which the sketch is drawn.

I think when in the end the author goes back to the interactive approach is basically his disappointment of not able to achieve the desired results or some solution other than knowledge based system. I think sketch recognition with the knowledge based systems is a perfect model to deal with this problem.