This document discusses interaction devices and their properties. It begins by defining input as sensed information about the physical environment, while output comprises any emission or modification to the physical environment. Pointing devices are then discussed in more detail, including their dimensions, whether they provide absolute or relative input, indirect vs direct interaction, and examples like mice, trackballs, and touchscreens. The document also examines the states of input devices and challenges in mapping these states to the demands of graphical user interfaces.

1. Dr. Shahzad Rasool
SCHOOL OF INTERDISCIPLINARY ENGINEERING AND SCIENCES (SINES)
Human Computer Interaction
CSE-868
Week 7. Interaction Devices (1)
14-18 MAR 2022

2. Interaction Devices
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3. Interaction Devices
• Input consists of sensed information about physical
environment
– e.g. mouse  senses movement across a surface
– Keyboard  detects a contact closure when the user presses a key
– Sensed information about physical properties of people, places, or
things
• Output can comprise any emission or modification to the
physical environment
– e.g. display (CRT, LEDs), speakers, tactile and force feedback devices
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4. Are I/P and O/P really distinct?
• A mouse without corresponding feedback (cursor)
• Sound and feel of the buttons when they are clicked?
• Sheet of paper  record ideas (input) and display
them (output)
• Clay reacts to the sculptor’s fingers yet
also provides feedback through the
curvature and texture of its surface
• More recently indivisibility of
input and output more evident
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5. Interaction Technique
• The fusion of input and output, consisting of all hardware and
software elements, that provides a way for the user to
accomplish a low-level task
– For example, in the traditional GUI, users scroll through a document by
clicking/dragging the mouse (input) within a scroll bar displayed on
the screen (output)
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Rapid info exchange
Role of HCI

6. Interaction Devices
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Faster, more natural, more convenient
Pleasant, efficient, salient
Constraints: human attention, cognition,
perceptual-motor skills and
abilities
Constraints: technologies and
methods
Where is current
research?

7. Interaction Tasks
• What interaction tasks are necessary for a particular
application
– Low-level primitive inputs required from the user
• For each task, choice of appropriate interaction technique
– Select optimal interaction technique for each task individually
– May lead to a poor overall design, with too many different or
inconsistent types of devices or dialogues
– Compromise on individual choices to reach a better overall design
• Several different ways of accomplishing the same task
– e.g. use a mouse to select a command by using a pop-up menu, a fixed
menu (a palette or command bar), multiple clicking, circling the
desired command, or even writing the name of the command with the
mouse
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8. Interaction Tasks
• What are these elemental tasks that appear repeatedly in
human-computer dialogs?
– Selection  Choosing objects from a set of alternatives
– Position  Specifying a position within a range. This includes picking a
screen coordinate with a pointing device
– Orient  Specifying an angle or three-dimensional orientation
– Path  Specifying a series of positions and/or orientations over time
– Quantify  Specifying an exact numeric value
– Text  Entry of symbolic data
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9. Interaction Tasks
• Are these really distinct?
• For example
– Position  Select a screen coordinate
using a pointing device
– Quantify  Enter a pair of numeric values
using a pair of knobs
– Elemental tasks elemental for some device may be subdivide-able into
subtasks for some other device
• Whether a task is “elemental” depends on the input device being used
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10. Interaction Tasks
• Are these the only elemental/fundamental/low-level tasks
– Which of these does a fingerprint scanner support?
• If used for password replacement  Text task?
• Or add ‘Establishment of Identity’ as a fundamental task?
• Where do devices like cameras, microphones, and fingerprint
scanner fit in?
• Advances in technology will yield new ‘elemental’ inputs
• Choice of device influences the level at which the user is
required to think about the individual actions that must be
performed to achieve a goal
– An interaction technique can encourage the user to work at the higher
level of the compound task
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11. The Choices in Interaction Design
1. Physical sensor
2. Feedback presented to the user
3. Ergonomic and industrial design of the device
4. Interplay between all of the interaction techniques
supported by a system
• For each of these, the choice space is too big
• Let’s look at input devices
– Continuous, manually operated pointing devices
– Discrete input mechanisms (buttons, keyboards, etc.)
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12. Pointing Devices
• Physical property sensed
– Typically sense position, motion, or force
• A tablet senses position
• A mouse measures motion (i.e. change in position)
• Isometric joystick senses force
– Rotary device, the corresponding properties are angle, change in
angle, and torque
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13. Pointing Devices
• Absolute input devices  position sensing devices
• Relative input devices  motion sensing devices
• Absolute devices can fully support relative motion by
calculating changes to position
• Relative device cannot fully support absolute positioning
– Can only emulate “position” at all times by introducing a cursor on
screen
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14. Pointing Devices
• No. of Dimensions
– Devices sense one or more input dimensions (degrees of freedom)
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Device Dimensions
Mouse 2 linear dimensions of motion
Knob 1 angular dimension
6DOF magnetic tracker 3 positions, 3 orientations
2 knobs 1D+1D
Mouse with scroll 2D + 1D

15. Pointing Devices
• No. of Dimensions
– No. of dimensions required by the user’s interaction task ≠ no. of
dimensions provided by input device?
– Special handling needed (e.g. additional DOFs using extra buttons,
mode switching, etc.)
– 3D interaction  Allow standard 2D pointing devices to control 3D
positioning/orientation
– Specialized multiple DOF input devices for superior performance?
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16. Pointing Devices
• Indirect vs Direct
• Are direct input devices always easier to use?
– Lack buttons for state transitions
– Occlusion  overlooked pop-up menus, dialogs, or status indicators
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The position of the cursor is controlled
by the device
• To indicate a point on the screen
Fingers manipulate visual objects on
the screen
• Unified input and display surface
Not necessarily

17. Pointing Devices
• Device acquisition time
– The average time to move one’s hand to a device
– Homing time  time to return from a device to a ‘home’ position
– Typically, effectiveness of a device for pointing usually tends to
dominate acquisition and homing time
– Overall performance  depends on how frequent is the switching
between pointing and non-pointing devices
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18. Pointing Devices
• Transfer Function
– Mapping from the input to output
– Typically, input signal modified using a mathematical transformation
that scales the data to provide stable and intuitive operation
• Force-to-velocity, position-to-position, and velocity-to-velocity
• e.g. isometric joystick  nonlinear rate mapping transforms force into
velocity of cursor movement
• e.g. Calculating scroll speed based on the position of mouse cursor
– Extending a selected region by dragging mouse close to the edge of screen
– No feedback of when or how much scrolling will accelerate
– Result  interaction is hard to learn to use and difficult to control
• Other metrics
– Pointing speed/accuracy, learning time, footprint, user preference,
comfort, cost, sampling rate, resolution, linearity
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19. Pointing Devices
• OS typically treats all input devices as virtual devices 
interchangeable
• Mouse
– 1967 – 2019 still favourite?
– Because its properties provide a good match between human
performance and the demands of graphical interfaces
– Mouse stays put when released  quick to reacquire
– Motion and button motion orthogonal  less accidental clicking
– Almost all muscle groups of the hand, wrist, arm, and shoulder
contribute to pointing  rapid, coarse movements and slow, precise
movements
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20. Pointing Devices
• Trackball
– Senses relative motion of partially exposed ball in two DOF
– Small working space (footprint)
– Allows use on an angled surface
– Requires frequent clutching movements
• Users must lift and reposition their hand after rolling a short distance
– Buttons located to the side of the ball  awkward to hold while rolling
– Different muscle groups than a mouse
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21. Pointing Devices
• Isometric Joysticks
– Force-sensing
– Self-calibration  Returns to centre
when released
– Rate of cursor movement is proportional to the force exerted
– Needs practice to achieve good cursor control
• Isotonic Joysticks
– Sense angle of deflection
– Absence of resistance, free movement
– Hybrid designs (isometric + isotonic) also possible
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Rate control
Position control

22. Pointing Devices
• Indirect tablets
– Report the absolute position of a pointer on a sensing surface
• Touch tablets  sense a bare finger
• Graphics/digitizing tablets  sense stylus or other physical intermediary
– On touch
• Cursor resumes motion from its previous position  relative mode
– For typical desktop interaction tasks such as selecting graphical icons or
navigating through menus
• Cursor jumps to the new position  absolute mode
– For tasks such as drawing, handwriting, tracing, or digitizing
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23. Pointing Devices
• Touchpads
– Small, touch-sensitive tablets often found on laptop computers
– Use relative mode for cursor control
• Too small to map to an entire screen
– Also have an absolute mode  features such as sliding along the edge
of the pad to scroll
– Clicking support  recognizing tapping or double-tapping gestures
– Accidental contact (or loss of contact) can erroneously trigger gestures
– Small size  Frequent clutching
– Awkward to use while holding down a button
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24. Pointing Devices
• Touch Screen / Pen operated devices
– Transparent, touch-sensitive tablets mounted on a display
– Parallax error  mismatch between the sensed input position and
apparent input position due to viewing angle
– Challenges  limited states and events sensed
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25. Pointing Devices
• Input Device States
– Generally three possible states (Buxton’s 3-state model)
• Out-of-range
• Tracking
• Dragging
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26. Pointing Devices
• Input Device States
– e.g. Mouse  two state device
• Cursor is being tracked or dragged
• Movement sensed in both states
– e.g. Touch-activated devices  two-state devices
• Dragging and Out of Range
• Difficult to support the same interaction techniques as a mouse
• Sliding finger on screen  move cursor or drag object?
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27. Pointing Devices
• Input Device States
– e.g. Pen-operated 3-state devices
• Senses location of stylus in proximity of screen
• Events triggered
– When contact established
– When entering/leaving proximity
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28. Pointing Devices
• Input Device States
– Even with all three states  still difficult for pen to support all
interaction techniques offered by mouse
– Let’s extend 3-state model for interaction with GUI
• Tracking
• Hover
• Left Click
• Dragging
• Right Click
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29. Pointing Devices
• Input Device States
– Mismatch between the demands of GUIs and states/events sensed by
touchscreens
– Need a way to signal when selecting something versus when just
moving over something to reach a desired target
– Hovering  for help text  hold the pointer motionless above display
– Difficult to perform with a pen or finger
• Pen operated devices lack current cursor position
• No second button for right click  timeout for right click?
– For rapid activation  as short as possible
– To avoid inadvertent activation  as long as possible
• Pen buttons  accidental press
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500ms  a reasonable
compromise