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Understanding & Modeling Input Devices. Björn Hartmann [email protected]. Questions for today. How do common input devices work? How can we think about the larger space of all possible input devices? Can we predict human input performance? - PowerPoint PPT Presentation
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Questions for today1. How do common input devices
work?2. How can we think about the larger
space of all possible input devices?3. Can we predict human input
performance?
Next class: What about uncommon input devices (music controllers, multitouch, …)?
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Today’s lecture in graph form
time
Level of abstraction
concretedetails
abstractmodels Functional
Dissection of Mouse & Keyboard
Design Space of
Input Devices Modeling
Human Performance
I spilled coffee on my keyboard. Now 25% of the keys don’t work anymore.But some of the defective keys are nowhere near the spill.What’s going on?
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Key cap
Top conductive layerBottom conductive layer
Separating layer(with hole)
Key cap
Top conductive layerBottom conductive layer
Separating layer(with hole)
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Row/Column Scanning
Q W E R T
A S D F G
Z X C V B
R1
R2
R3
R4
C1 C2 C3 C4 C59 lines
20 keys
Mouse. Engelbart and English ~1964Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.
A Layered Framework
12From: Hartmann, Follmer, Klemmer: Input Devices are like Onions
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Right button
Left buttonEncoder wheel for scrolling
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IR emitter IR detectorslotted wheel(between emitter & detector)
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Sensing: Rotary Encoder
High
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Sensing: Fwd Rotation
Low
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Sensing: Backwd Rotation
Low Oops!
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Solution: Use two out-of-phase detectors
HighHigh
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Sensing: Rotary Encoder
LowHigh
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Sensing: Rotary Encoder
HighLow
Coding:HH-> LH: dx = 1HH-> HL: dx = -1
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Transformationcxt = max(0, min( sw, cxt-1+dx*cd ))cyt = …
cxt: cursor x position in screen coordinates at time tdx: mouse x movement delta in mouse coordinatessw: screen widthcd: control-display ratio
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Device Abstraction Click, DoubleClick, MouseUp,
MouseDown, MouseMove …
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What about optical mice?
Source: http://spritesmods.com/?art=mouseeye
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bbbbbbbbbb
Source: http://spritesmods.com/?art=mouseeye
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Trackball, Trackpad
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Trackpoint Indirect, force sensing, velocity
control Nonlinear transfer function
Force
Velo
city
(cc) Image by flickr user tsaiid
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Joysticks
A design space of input devices…
Card, S. K., Mackinlay, J. D., and Robertson, G. G. 1991. A morphological analysis of the design space of input devices. ACM TOIS 9, 2 (Apr. 1991), 99-122.
Implicit Assumptions: Desktop-centric computing
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Which device is fastest? For what task? Pointing.
Combination of two factors: Bandwidth of human muscle group
(upper limit) Bandwidth of device itself
Bandwidth of Human Muscle Groups
Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.
Fitts’ Law Time Tpos to move the hand to
target size S which is distance D away is given by: Tpos = a + b log2 (2D/S)
Time to move the hand depends only on the relative precision required
Source: Landay, James. “Human Abilities”. CS160 UC Berkeley.
Mouse vs. Headmouse
Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.
Headmouse: No chance to win
Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.
Fitts’ Law in Windows & Mac OS
Windows 95: Missed by a pixelWindows XP: Good to the last drop
The Apple menu in Mac OS X v10.4 Tiger.
Source: Jensen Harris, An Office User Interface Blog : Giving You Fitts. Microsoft, 2007; Apple
Fitts’ Law in Microsoft Office 2007
Larger, labeled controls can be clicked more quickly
Mini Toolbar: Close to the cursor
Magic Corner: Office Button in the upper-left corner
Source: Jensen Harris, An Office User Interface Blog : Giving You Fitts. Microsoft, 2007.
stanford hci group Feb 9, 2009
http://bjoern.org
