by Tracy Hammond and Kenneth Mock
Comments
1. Daniel's blog
Summary
The paper begins with the introduction of the first pen-based computer interaction system -- Sketchpad (1963) and the advantages of raster graphics over vecter graphics (fill areas with solid colors or patterns, refreash independent of complexity of the scene) are stated. Then active and passive digitizers are introduces, and advantages and disadvantages of both techniques are weighed: passive digitizer (easy touch by finger but cursor jumps and hard to perform right-clicking), active digitizer (electromagnetic pens used, "hover" cursor, right-clicking and erasing with pen, but rely on special pen and inaccurate near borders). Afterwards, several kind of hardware (tablet PC slate, Cintiq, SMART board, USB-connected pen tablet) and software (TIP on Windows Vista, Inkwell on Apple, additional drive like Jarnal on Linux, Camtasia) are introduded. Specifically, tablet-based pedagogy shows great success up till now, instructors can make comments on PowerPoint to enable flexibility during class, tablet is also quite useful in aiding the input of diagrams for lectures, equations and graphs in students' homework, etc., also, using tablets in class helps to gather students' attention, because slates can be laid flat on desk so that the instructor can see what a student is working on. Next, the author states use of sketch recognition in different fields (music, ChemPad in chemistry, LADDER MechEng in mechanical engineering, LADDER FSM in finite state machine). The FLUID framework enables development of sketch interface, of which GUILD enables building shape description through drawing. At last, two case studies of tablets use in class are given, both show that tablets have positive effect in maths teaching. Future directions states the great potential in tablet sketching field.
Discussion
Through this paper, we are informed of various kind of sketch recognition devices and systems in use. The initial success of tablet-based teaching and study in such classes as music, mechanical engineering, calculus and algebra is a useful experience which is worth being extended into other classes like literature, history, etc. And I believe, with our effort and the advancement of technology, new sketch recognition systems will emerge at tremendous speed.
Thursday, August 28, 2008
"Sketch Pad: A Man-machine Graphical Communication System"
by Sutherland
Comments
1. Akshay's blog
Summary
The author first showed us an example of using light pen to draw a hexagon as well as to point to parts of the existing hexagon and apply certain "constraint" (corners on a circle) and "definition copying" (sides of equal length) to it to make it regular. And thereafter, this hexagon was served as a "subpicture", and by attaching a numerous of such subpictures together, a pattern was produced. What's worth mentioning is that Sketchpad stores how various parts of the drawing are related and the structure of the subpictures used.
Then he explained the implementation of Sketchpad. The data storage structures used: n-component objects are stored in ring structures, in which members can be added, removed or modified. Additionally, generic headings of the rings are collected together as generic types, which may in turn gathered under super-generic blocks to form a hierarchical structure. A light pen is used in the system, the user should touch existing line or spot on the display to initialize, and when pointing to existing object, a "pseudo pen location" is displayed to indicate "aim at" if the exact position falls within a distance to the object. The system can display drawing of a range of magnification of 2000 and compute which part is to be shown on the display, and positions of spots on lines and circles are computed with difference equations. Sketchpad can also display digits and texts. And for easy manipulation, abstractions such as constraints and scalar value can even be displayed. Recursive functions are used when dealing with deleting, merging and display of instances. Attachers (points, lines, cirles, etc.) allow objects to integrate. Attachers will recursively merge objects of like type when copying occurs, and when copying instances, the copy losses all identity as a unit. Moreover, copying allows duplication of not only objects, but constraints as well. As for constraints, Sketchpad applies the fast one pass method before trying the slow but reliable relaxation method.
In the last part, examples (patterns, linkages, dimension lines, bridges, artistic drawings, circuit diagrams) were illustrated and conclusions were drawn.
Discussion
This paper shows the first pen-based computer interaction system in the world, as early as 1963. It must be an amazing work at that year. The system is really versatile, the hierarchical structure of generic type enables drawing of objects composed of simpler components that are already known. And by copying and attachers, users can produce complicated drawings which has thousands of parts. The function of constraints is actually quite strong, you can define certain properties of objects and relation between them, so I'd say it's really the highlight of this system.
In term of sketch recognition, however, Sketchpad is nothing more than a computer-assisted drawing pad, users have to push buttons and turn knob from time to time to tell the computer what is to be drawn and what effects they are expecting, drawing with Sketchpad is a totally manipulated process rather than automatic analysis and understanding by the computer itself.
Comments
1. Akshay's blog
Summary
The author first showed us an example of using light pen to draw a hexagon as well as to point to parts of the existing hexagon and apply certain "constraint" (corners on a circle) and "definition copying" (sides of equal length) to it to make it regular. And thereafter, this hexagon was served as a "subpicture", and by attaching a numerous of such subpictures together, a pattern was produced. What's worth mentioning is that Sketchpad stores how various parts of the drawing are related and the structure of the subpictures used.
Then he explained the implementation of Sketchpad. The data storage structures used: n-component objects are stored in ring structures, in which members can be added, removed or modified. Additionally, generic headings of the rings are collected together as generic types, which may in turn gathered under super-generic blocks to form a hierarchical structure. A light pen is used in the system, the user should touch existing line or spot on the display to initialize, and when pointing to existing object, a "pseudo pen location" is displayed to indicate "aim at" if the exact position falls within a distance to the object. The system can display drawing of a range of magnification of 2000 and compute which part is to be shown on the display, and positions of spots on lines and circles are computed with difference equations. Sketchpad can also display digits and texts. And for easy manipulation, abstractions such as constraints and scalar value can even be displayed. Recursive functions are used when dealing with deleting, merging and display of instances. Attachers (points, lines, cirles, etc.) allow objects to integrate. Attachers will recursively merge objects of like type when copying occurs, and when copying instances, the copy losses all identity as a unit. Moreover, copying allows duplication of not only objects, but constraints as well. As for constraints, Sketchpad applies the fast one pass method before trying the slow but reliable relaxation method.
In the last part, examples (patterns, linkages, dimension lines, bridges, artistic drawings, circuit diagrams) were illustrated and conclusions were drawn.
Discussion
This paper shows the first pen-based computer interaction system in the world, as early as 1963. It must be an amazing work at that year. The system is really versatile, the hierarchical structure of generic type enables drawing of objects composed of simpler components that are already known. And by copying and attachers, users can produce complicated drawings which has thousands of parts. The function of constraints is actually quite strong, you can define certain properties of objects and relation between them, so I'd say it's really the highlight of this system.
In term of sketch recognition, however, Sketchpad is nothing more than a computer-assisted drawing pad, users have to push buttons and turn knob from time to time to tell the computer what is to be drawn and what effects they are expecting, drawing with Sketchpad is a totally manipulated process rather than automatic analysis and understanding by the computer itself.
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