tech-reports@cl.cam.ac.uk
07-25-2004, 02:49 AM
Publication announcement:
Sketchpad: A man-machine graphical communication system
Ivan Edward Sutherland
Technical report UCAM-CL-TR-574, University of Cambridge,
Computer Laboratory, September 2003, 149 pages.
New preface by Alan Blackwell and Kerry Rodden.
This document is now available at
http://www.cl.cam.ac.uk/TechReports/UCAM-CL-TR-574.pdf
Abstract:
The Sketchpad system uses drawing as a novel communication medium for a
computer. The system contains input, output, and computation programs
which enable it to interpret information drawn directly on a computer
display. It has been used to draw electrical, mechanical, scientific,
mathematical, and animated drawings; it is a general purpose system.
Sketchpad has shown the most usefulness as an aid to the understanding
of processes, such as the notion of linkages, which can be described
with pictures. Sketchpad also makes it easy to draw highly repetitive or
highly accurate drawings and to change drawings previously drawn with
it. The many drawings in this thesis were all made with Sketchpad.
A Sketchpad user sketches directly on a computer display with a "light
pen." The light pen is used both to position parts of the drawing on the
display and to point to them to change them. A set of push buttons
controls the changes to be made such as "erase," or "move." Except for
legends, no written language is used.
Information sketched can include straight line segments and circle arcs.
Arbitrary symbols may be defined from any collection of line segments,
circle arcs, and previously defined symbols. A user may define and use
as many symbols as he wishes. Any change in the definition of a symbol
is at once seen wherever that symbol appears.
Sketchpad stores explicit information about the topology of a drawing.
If the user moves one vertex of a polygon, both adjacent sides will be
moved. If the user moves a symbol, all lines attached to that symbol
will automatically move to stay attached to it. The topological
connections of the drawing are automatically indicated by the user as he
sketches. Since Sketchpad is able to accept topological information from
a human being in a picture language perfectly natural to the human, it
can be used as an input program for computation programs which require
topological data, e.g., circuit simulators.
Sketchpad itself is able to move parts of the drawing around to meet new
conditions which the user may apply to them. The user indicates
conditions with the light pen and push buttons. For example, to make two
lines parallel, he successively points to the lines with the light pen
and presses a button. The conditions themselves are displayed on the
drawing so that they may be erased or changed with the light pen
language. Any combination of conditions can be defined as a composite
condition and applied in one step.
It is easy to add entirely new types of conditions to Sketchpad's
vocabulary. Since the conditions can involve anything computable,
Sketchpad can be used for a very wide range of problems. For example,
Sketchpad has been used to find the distribution of forces in the
members of truss bridges drawn with it.
Sketchpad drawings are stored in the computer in a specially designed
"ring" structure. The ring structure features rapid processing of
topological information with no searching at all. The basic operations
used in Sketchpad for manipulating the ring structure are described.
--
University of Cambridge, Computer Laboratory,
Technical Reports (ISSN 1476-2986)
http://www.cl.cam.ac.uk/TechReports/
Sketchpad: A man-machine graphical communication system
Ivan Edward Sutherland
Technical report UCAM-CL-TR-574, University of Cambridge,
Computer Laboratory, September 2003, 149 pages.
New preface by Alan Blackwell and Kerry Rodden.
This document is now available at
http://www.cl.cam.ac.uk/TechReports/UCAM-CL-TR-574.pdf
Abstract:
The Sketchpad system uses drawing as a novel communication medium for a
computer. The system contains input, output, and computation programs
which enable it to interpret information drawn directly on a computer
display. It has been used to draw electrical, mechanical, scientific,
mathematical, and animated drawings; it is a general purpose system.
Sketchpad has shown the most usefulness as an aid to the understanding
of processes, such as the notion of linkages, which can be described
with pictures. Sketchpad also makes it easy to draw highly repetitive or
highly accurate drawings and to change drawings previously drawn with
it. The many drawings in this thesis were all made with Sketchpad.
A Sketchpad user sketches directly on a computer display with a "light
pen." The light pen is used both to position parts of the drawing on the
display and to point to them to change them. A set of push buttons
controls the changes to be made such as "erase," or "move." Except for
legends, no written language is used.
Information sketched can include straight line segments and circle arcs.
Arbitrary symbols may be defined from any collection of line segments,
circle arcs, and previously defined symbols. A user may define and use
as many symbols as he wishes. Any change in the definition of a symbol
is at once seen wherever that symbol appears.
Sketchpad stores explicit information about the topology of a drawing.
If the user moves one vertex of a polygon, both adjacent sides will be
moved. If the user moves a symbol, all lines attached to that symbol
will automatically move to stay attached to it. The topological
connections of the drawing are automatically indicated by the user as he
sketches. Since Sketchpad is able to accept topological information from
a human being in a picture language perfectly natural to the human, it
can be used as an input program for computation programs which require
topological data, e.g., circuit simulators.
Sketchpad itself is able to move parts of the drawing around to meet new
conditions which the user may apply to them. The user indicates
conditions with the light pen and push buttons. For example, to make two
lines parallel, he successively points to the lines with the light pen
and presses a button. The conditions themselves are displayed on the
drawing so that they may be erased or changed with the light pen
language. Any combination of conditions can be defined as a composite
condition and applied in one step.
It is easy to add entirely new types of conditions to Sketchpad's
vocabulary. Since the conditions can involve anything computable,
Sketchpad can be used for a very wide range of problems. For example,
Sketchpad has been used to find the distribution of forces in the
members of truss bridges drawn with it.
Sketchpad drawings are stored in the computer in a specially designed
"ring" structure. The ring structure features rapid processing of
topological information with no searching at all. The basic operations
used in Sketchpad for manipulating the ring structure are described.
--
University of Cambridge, Computer Laboratory,
Technical Reports (ISSN 1476-2986)
http://www.cl.cam.ac.uk/TechReports/