input (part 1: devices)
TRANSCRIPT
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Input (part 1: devices)
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Where we are...
Two largest aspects of building interactive systems: output and input Have looked at basics of output Now look at input
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Input
Generally, input is somewhat harder than output Less uniformity, more of a moving target More affected by human properties Not as mature
Will start with low level (devices) and work up to higher level
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Input devices
Keyboard Ubiquitous, but somewhat boring… Quite mature design
QWERTY key layout Where did it come from?
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QWERTY key layout
Originally designed to spread out likely adjacent key presses to overcome jamming problem of very early mechanical typewriters Often quoted as “intentionally
slowing down” typing, but that’snot true Arrangement of letters to keep
typebars from getting stuck (Common letter pairs on
alternating hands)
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QWERTY keyboard layout
Other layouts have been proposed Dvorak is best known Widely seen as better Experimental and theoretical evidence casts doubt on this
Alternating hands of QWERTY are a win since fingers move in parallel
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QWERTY keyboard layout
Whether or not Dvorak layout is better, it did not displace QWERTY Lesson: once there is sufficient critical mass for a standard it is
nearly impossible to dislodge (even if there is an apparently good reason to do so)
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Keyboards
Repetitive Stress Injury First comes up here, mouse tends to be a little worse for
most people
Take this seriously for yourself! Can be a VERY bit deal Biggest thing: adjust your work environment (e.g. chair height)
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Buttons
Similar to keyboard, but not for typing letters but for symbols separate collection of keys with typically same form but
different purpose now see as “function keys” that come standard with
keyboards also show up on e.g., mouse
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Buttons
Buttons often bound to particular commands e.g., function keys Improved quite a bit with labels Software changeable labels would be ideal, but we don’t
typically get this
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Valuators
Returns a single value in range Major impl. alternatives:
Potentiometer (variable resistor) similar to typical volume control
Shaft encoders sense incremental movements
Differences?
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Valuator alternatives Potentiometer
normally bounded range of physical movement (hence bounded range of input values)
Keeps residual position in device Shaft encoder
Unbounded range of movement No residual position in device
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Locators (AKA pointing devices)
Returns a location (point) two values in ranges usually screen position
Examples Mice (current defacto standard) Track balls, joysticks, tablets, touch panels, etc.
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Locators
Two major categories: Absolute vs. Relative locators
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Absolute locators One-to-one mapping from device movement to input
e.g., tablet Faster Easier to develop motor skills Doesn’t scale past fixed distances
bounded input range less accurate (for same range of physical movement)
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Relative locators
Maps movement into rate of change of input e.g., joystick (or TrackPoint)
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Relative locators
More accurate (for same range of movement) Harder to develop motor skills Not bounded (can handle infinite moves)
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Q: is a mouse a relative or absolute locator?
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Q: is a mouse a relative or absolute locator?
Answer: No Third major type:
“Clutched absolute” Within a range its absolute Can disengage movement (pick it up) to extend beyond
range picking up == clutch mechanism
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Clutched absolute locators
Very good compromise Get one-to-one mapping when “in range” (easy to learn, fast,
etc.) Clutch gives some of benefits of a relative device (e.g.,
unbounded)
Trackballs also fall into this category
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Device specifics: joysticks self centering relative device possible to have absolute joysticks, but scaling is bad
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Joystick construction
Two potentiometers x and y resistance is a function
of position
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Joystick construction
Two potentiometers x and y resistance is a function
of position
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Joystick construction
TrackPoint (IBM technology) uses strain gauge sensors
Also can be implemented with switches one in each direction Fixed speed of movement
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Trackballs
(Typically large) ball which rolls over 2 wheels
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Trackballs
Clutched absolute but with small movement range
Infinite input range, etc. Properties vary quite a bit
scaling of movements mass of ball
high mass ball can act as a relative device by spinning it
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Mouse
Clutched absolute infinite range, etc.
How is it constructed?
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Mouse
Clutched absolute infinite range, etc.
How is it constructed? Turn a trackball upside down
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Mouse
Current dominant device so much so that some people call any pointing device a
“mouse” overall a very good device
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Mouse
Invented by Douglas Engelbart et al. ~1967
http://sloan.stanford.edu/MouseSite/Archive/AugmentingHumanIntellect62/Display1967.html
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Touch panel
What kind of a device?
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Touch panel
Absolute device Possible to do input and output together in one place
actually point at things on the screen Resolution limited by size of finger (“digital input”)
Or requires a pen
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Touch panel construction
Membrane resistive, fine wire mesh
Capacitive Optical
finger breaks light beam Surface acoustic waves
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Drawing tablet
Absolute or relative?
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Drawing tablet
Absolute device Normally used with pen / stylus
Allows “real drawing” (try drawing with a mouse vs. a pen) Can often trace over paper images
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Construction of drawing tablet
Traditional (“Rand”) tablet middle 60’s grid of wires (~100 / inch) each wire transmits binary of its coord stylus picks up closest
Can also make pen transmitter and tablet receiver
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Drawing tablet details
Typically have tip switch May also have switch(es) on side of stylus Can also support a “puck” with buttons Best current devices can support multiple “pens” at the same
time and sense rotation of a puck
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Alternate Approaches to Tablets
Old acoustic (sort of a fun device) stylus emits spark strip microphones at edge of tablet difference in arrival time of sound
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Interesting device: Virtual Ink Mimio
Updated acoustic tablet recording whiteboard ultrasonic chirps 100dpi resolution over ~8ft
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3D locators
Can extend locators to 3 inputs Some fun older devices
3D acoustic tablet Wand on reels Multi-axis joystick
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3D locators
Typical for VR use: Polhemus 6D device (x,y,z + pitch, roll, yaw) Magnetic sensing technology
Doesn’t work well near metal Doesn’t work well near deflection coils of CRT
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Light pen (a very old device)
A “pick” device returns ID of an “object” on the screen (not a position)
For vector refresh displays Vector refresh worked with small “display list processor” Add register holding current obj ID Photocell causes interrupt when beam passes (grab and
return ID)
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Light pen (a very old device)
Can’t really do this anymore on raster display light pen is just a locator
But its conceptually what we usually want for input: what object the user is pointing at We will simulate in SW (“picking”)
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Lots of other devices
Still mostly KB + mouse, but increasing diversity Cameras!
Lots of untapped potential in vision Microphones
speech as data speech recognition
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Lots of other devices
Any favorites?
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Some interesting ones I know about
Thumb Wheel DataGlove Motion detectors (and other sensors) Accelerometers Fingerprint readers RF tags (physical objects as tokens for data/action) Sub-gram resolution scales
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