Sketchpad

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Akshay's blog

Summary

Sketchpad basically is one major breakthrough in the field of sketch recognition. Ivan E. Sutherland consultant Lincoln lab of the MIT is the creator of sketchpad. A sketchpad in simple terms is a device which enable human beings to draw digital diagrams using a light pen. The resulting diagram can be easily manipulated on the computer screen.

Considering sketchpad was built in 1963 with the limited resources of the time a simple task involved a lot of complexities. Sketchpad on its conception only supported a set of predefined shapes for example lines, circles and points to be made on the screen. But it was designed in such a way which could cater more shapes such as ellipse etc. Sketch pad also provided other functionality of joining points, adding constraints, copying, merging, deletion, rotation and magnification of the diagrams. Its usefulness at that time was expected to be in the field of the topological input devices and highly repetitive diagrams.

Sketchpad also have the capability of displaying 'text' and 'numbers'. In sketchpad the letters and the numbers are more or less the combination of curves and lines. Sketchpad utilizes some recursive functions to be able to manipulate the diagrams. 1) Expansion of instances: which means its possible to have sub pictures within sub pictures 2) Recursive deletion: which is deleting an object also means the deletion of all depended objects. 3) Recursive merging: which means merging of two independent objects will result in all the dependent objects to be now dependent upon the result of the merger. Sketchpad also use 'recursive display' to display diagrams on the screen. For every instance to be drawn it breaks the picture into the smaller part which was earlier drawn and so on until the it could not broken down into any smaller instance.

Sketchpad can also define 'attachers' since small diagrams can be used to make a larger diagram and these smaller parts need to be connected with other parts so the user must define the attachers in smaller parts so these pieces can be joined. Sketchpad apart from the light pen also uses a set of buttons which actually tells the sketchpad when a copy operation is to be performed or when a delete operation is to be performed and so forth. What makes sketchpad different from the paper and pencil concept is that in sketchpad the user can define the design constraints. For example user can define a constraint that two particular lines will be parallel. If the user had not drawn the two lines parallel to each other the computer will adjust the diagram so the two lines become parallel. There are a set of constraints which are compiled in the form of a manual for the user. This makes it easier for the user to draw as he/she wishes to draw by utilizing these constraints.

Discussion

Although it has been four decades since the sketchpad was developed but still it proposes some very futuristic concepts. Sketchpad was developed as the first pen based input device on computers but its use and progress was marred by the concurrent invention of a computer mouse. Since the computer mouse was a cheaper built and pen-based device was very expensive sketchpad didn't get much attention of the researchers.

The fault that I see in this system but that can be justified is that the system rely a lot on user input. To posses the system was actually very expensive at that time and it seems that it was equally difficult to use the it also.

If I had invented this sketchpad I would have definitely gone onto the next level to make this device more user friendly and accessible to common people for use in activities such as teaching, planning and simulation.