Transcript Slides for Lecture 3

Lecture 3:
Pointing Devices and Fitts’ Law
Brad Myers
05-440/05-640: Interaction Techniques
Spring, 2016
© 2016 - Brad Myers
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Topics
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Note: “pointer” or “pointing device” (not “mouse”)
Types of pointing devices
Various properties:
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Direct vs. indirect
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Cursor?
Relative vs. absolute
Rate vs. position controlled (esp. for joysticks)
How many states supported? (hover?, not-pressed?)
Single or multiple touch
Measuring effectiveness
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Important measures:
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Speed, accuracy, comfort, learnability
Fitts’ law
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© 2016 - Brad Myers
Some Pointing Devices
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(List from HW#1):
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Mouse
Laptop touchpad
IBM Pointing Stick on Thinkpad laptops
Touchscreen with fingers (phones, tablets)
Touchscreen with Stylus
Wii controller pointer in the air, pointing at a web page on a "smart TV"
Microsoft Kinect using your hand to point at a web page on a "smart TV"
Large "Smart Board" direct touch wall-size display
Game controller connected to a PC to control the cursor
Contour's "RollerMouse Red plus"
Trackball
Others
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Step keys
Light pen
Laser pointer at a screen
Joysticks
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Game consoles
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“Cursor”
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Same word used for both pointer position and
text input position
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Text cursor
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Are usually different
Will discuss with text entry lecture
Pointer’s cursor often changes
shape to show next action
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“Cursor” in this lecture
Often no pointer cursor if
direct touch
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© 2016 - Brad Myers
Light pen
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Starting ~ 1950s
Sketchpad, 1963
Camera in pen looks for
pixel on screen
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Calculates
position based
on timing
Disadvantages:
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Need to hold
hand in the air
Low resolution
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Photo credit: https://design.osu.edu/carlson/history/lesson2.html
© 2016 - Brad Myers
Step Keys
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Usually to move text cursor
Sometimes can move
pointer cursor as well
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Microsoft Windows, can
move window with ALTSpace, “m”, arrow-keys
Moves pointer cursor as well
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© 2016 - Brad Myers
Mouse
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Bill English and Doug Engelbart
credited with the invention of the
mouse (1967)
Comfortable, fast and accurate
Engineered to not move when push
a button
Cursor moves straight as hand
moves in an arc
Various gain functions
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Pixels per cm
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© 2016 - Brad Myers
Joysticks
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Often used in aviation
Computer input for games
Most are “rate controlled”
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self-centering springs
Movement controls rate of cursor
movement
“isometric” – stick doesn’t seem to move
Position controlled
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Absolute position of stick controls
position
No spring – stick stays where leave it
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© 2016 - Brad Myers
IBM Pointing Stick
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See lecture from 2014 from Ted Selker
“Trackpoint”
Rate-controlled isometric joystick
Significant iteration and experimentation
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“10 years of human factors work”
Material of the stick matters
Placement of buttons
Transfer function
Training helps performance
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© 2016 - Brad Myers
Tablets
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Rand Tablet: 1964:
http://www.rand.org/content/dam/rand/pubs/research_memoranda/2005/RM4122.pdf
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Handwriting and graphics input
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CAD/CAM
Move stylus or puck or finger on a surface –
not a display screen
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© 2016 - Brad Myers
Touchscreens
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Stylus versus finger
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Tradeoffs:
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Naturalness
Accuracy
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Amount of content that can fit on the screen
Blocking the view of the content
How hold a tablet?
Palm & hand removal?
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© 2016 - Brad Myers
Large Touchscreens
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Projector or TV
Vertical or tabletop
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Smartboard
Original Microsoft
“surface”
Single or multiple people
Classrooms, museums,
small meetings, etc.
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© 2016 - Brad Myers
Remote interaction with
large screens
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Examples
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Laser pointing at screen
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Brad A. Myers, et. al. "Interacting At a Distance: Measuring the
Performance of Laser Pointers and Other Devices." CHI'2002.
pp. 33-40. pdf.
Wii controller
Microsoft Kinect – just fingers
Very inaccurate
Tiring
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© 2016 - Brad Myers
Issues
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Direct vs. Indirect
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Direct – point at a screen
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Indirect – movement moves a cursor
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Light-pen, stylus, finger
Often no visible cursor
More natural
Image credit:
http://www.drdigitizer.com/learn.html
Must be learned
Issue – direction of movement (up or down is arbitrary)
Transfer function – can be more accurate and faster
Must have a cursor – Shape can be used as feedback
Software can move position of the cursor
Relative vs. absolute
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Relative – only movement used = mouse
Absolute – required for touchscreen
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Touchpads can be either
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© 2016 - Brad Myers
Issues, 2
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How many states supported?
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Can have “hover” state?
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How many buttons?
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Pointing but not “pressed” or “selected”
Common with mouse, not with touchscreen
Is possible with magnetic stylus on touchscreen
Location but not pressed
Stylus buttons on side of pen
Other dimensions, like force of press – “3D touch”
Single or multiple touch
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Resistive vs. capacitive vs. other sensing
For big displays – which person’s hand?
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© 2016 - Brad Myers
Testing
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How decide whether an input device is “better”
than another?
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Important measures: speed, accuracy, comfort,
learnability
As usual in HCI, need to decide tasks and relative
importance of measures
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Often (but not always) will have tradeoffs
Focus on speed and accuracy
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Since are numeric, can use standard statistical
measures
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JMP, R, SPSS, Excel, and others to help with calculations
Fitts law
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Slides by Jeffrey Rzeszotarski
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© 2016 - Brad Myers
Fitts’ Law
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1954, Paul Fitts
Figure out how quickly people could move a
pointing device to a target and select it
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Predictive model
 e.g., keystroke-level analysis
To compare pointing devices
 Throughput – combines both speed and
accuracy
+
Cognitive Processes + Physical Processes
=
Pointing Performance
Laser Pointer
Example
Source: hcibook.com
Card, Moran, Newell
studies
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Card, English, Burr 1978
paper – distance
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Time is linear for distance for
step keys
Time increases with the log of
the distance for continuous
devices like the mouse
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© 2016 - Brad Myers
Card, Moran, Newell studies, 2
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Card, English, Burr 1978
paper – width
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Positioning time for both
the mouse and the
joystick decreases
with the log of the
target size
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© 2016 - Brad Myers
T = a + b log2(D/W + 1)
T = time to complete a movement
 a = fixed cost to start/stop moving &
click
 b = inherent speed of device
 log2(D/W + 1) = “index of difficulty” or ID bits
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Higher with distance (D) and lower with width (W)
ID = log2(D/W + 1)
“double the distance, double the width”
equals
Card, English, Burr 1978
Homework 1 Analysis
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You can actually do this with your data!
The Fitts’ Tester spreadsheet (on
Blackboard) roughly follows Card et al.
experiment
Compute IDs from Distance and Width
Chart them and see if they are linear
Use Excel “Fit Trendline” to get coefficients
for a and b and compare to other papers
Homework 1 Analysis
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Keep in mind that the papers you read
collected MUCH more data
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E.g., 1200 to 1800 trials (four to six hours) before
learning curve flattened out – [Card, 1978]
It’s okay to not have any measurable
difference as long as you explain why that’s
reasonable
Check out the error rates too
The laser pointer paper is good example of
how to structure a report
Newer Fitts’ Law tests
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Use circles instead of two rectangles
ISO 9241-9 standard
Doesn’t fit as well on non-square screens
Horizontal and vertical movements may not be
equal difficulty
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Muscles used
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Card, English, Burr 1978 paper showed differences
for joystick, etc. but not mouse
Laser pointer study: up to 10x more wiggle vertically
Device properties
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Contour's "RollerMouse Red plus"
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© 2016 - Brad Myers
Homework 1
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Questions?
Tom Moran
Bill Curtis, Stu Card, and Allen Newell
Source: SIGCHI Archives