User Interface Technology Flashcards
1
Q
User Interfaces
A
- The user inteface is the part of a system through which a user can interact, composed of software and/or hardware that supports input, output or both.
- Not restricted to digital and interactive systems
- Examples:
- Graphical user interface (GUI) of any app or system,
e.g. of search engine, or powerpoint - Voice user interface in a smart speaker (e.g. Alexa)
- Buttons, switches, wheels and levers in a cockpit
- Control panel of everyday devices,
e.g. microwave oven, alarm cock, …
2
Q
Human-Computer Input/Output
A
- Input from the user to the system via sensors/controls
- Output from the system via displays/actuators
3
Q
Input Technologies
A
4
Q
Examples of Input Tasks
A
- Filling in a form
- Pointing/selection, text input
- Mobile food order
- Media capture, pointing/selecting
- Data-entry device (assignment 3)
- Directly mapped controls
- Whack-A-Mole (assignment 2)
- Pointing/selection
5
Q
Input devices
A
- “An input device is a transducer from the physical properties of the world into the logical parameters of an application” (B.Buxton)
- Keys, buttons, touch sensors - sensing discrete input
- Pointing devices - sensing spatial input in one or more dimensions
- Input devices can also be based on touchless sensing
- Audio - for voice control
- Video - e.g., mid-air gestures, facial expressions, …
- Depth sensors - body interface, proxemic interaction
6
Q
Control Interfaces
A
- Conventional control interfaces
- Input/controls: Buttons, knobs, pedals, …
- Output/feedback: Lights, beeps, instruments
- Physical: hard controls
- Single-purpose
- Separate input and output
- Hard-wired control-display relationships
7
Q
Computer Interfaces
A
- Physical interface
- Multi-purpose I/O devices
- Keyboard, pointing device, microphone, camera
- Displays, speaker, printer
- Soft interface
- Graphical controls and views
- Rendered on physical display
- Controlled with input devices
8
Q
Hard versus soft interfaces
A
- Hard controls: input distinct from output, rigid control-display mappings
- Soft interfaces: blending input and output, flexible and dynamic control-display mappings, using general purpose input/output hardware
- Device trends: fewer components, soft controls are cheaper and more flexible
- Physicality remains important for many tasks and situations
- e.g., faster typing, eyes-free input, industrial application, safety-critical
9
Q
Soft interfaces
A
- Soft interfaces transform possibilities for control and interaction
- More controls in less space
- Use of the same display space can instantly change during the interaction
- Use the same physical input devices for any number of different controls
- Small set of input events
- What they control depends on the state of the interface at the time of input
10
Q
Blending Input/Output
A
- Soft interfaces blend the distinction between control and display
- Soft controls are rendered on a display and have the properties of displays
- Feedforward on available actions
- Static labels, Preview on hover
- Feedback on system status
- e.g., Switch on/off, Position on scale
- Feedback during the control action
- e.g., continuous feedback in adjusting values on a scale
11
Q
Control-Display Relationships
A
- A control-display relationship is a mapping from input to output
- Soft interfaces lead to complex control-display relationships
- Every possible action on a soft control that produces a visible response is a control-display relationship
- Soft controls can respond to different physical control events
- Click, double-click, drag, shift-click, control-click, keyboard shortcut, …
- Controls can trigger different responses (displays) depending on context
- Different modes of the interface
12
Q
Modes
A
- Modes are different interpretations of the user input by the system, depending on the state of the interface
- Same input, different results
- Caps Lock switches keyboard mode
- Modes in camera app change effect of shutter button
- Language modes in text entry effect prediction
- Modeless interfaces
- same user input will have the same result
- regardless of the system state
13
Q
Usability of Modes
A
- Modes solve the problem of supporting more
functions than there are controls - e.g. Photoshop:
- mouse input in different modes
- switched by selecting tools (brush, eraser, …)
- cursor shape to provide feedback on mode
- Usability issues
- Hard to discover how modes are switched
- Not clear what the current mode is
- Common with hard control interfaces (appliances)
14
Q
Mode errors
A
- Mode errors occur when the user is not
aware of the current mode - Example: Airbus-320 crash, Strasbourg 1991
- Modes for specifying descent as FPA (angle) or VS (vert. speed)
- Pilot input “-3.3” assuming FPA mode (same as 800 ft/min)
- But the control was in VS mode, with the input interpreted as -33 x 100 feet/min
15
Q
Pointing devices
A
- Pointing devices enable input of spatial data, for a wide range of tasks
- Object selection, positioning, manipulation, drawing, quantifying input, …
- Pointing devices are characterized by:
- Continuous sensing in motor space (= input space)
- Continuous mapping of the sensed property to control a point in display space (= output space)
- A specific control-display relationship defined by a transfer function
16
Q
Devices and Technologies
A
- “Classic” pointing devices for graphical user interfaces (2D)
- Mouse for pointing on desktop computers
- Touchpad for pointing on laptops
- Joystick on game controllers
- Trackball (“mouse upside down”)
- Pointing stick (trackpoint)
- Touchscreen and stylus are also pointing devices (in addition to other functions)
- Pointing devices for 3D environments (6 DOF)
- Eye trackers for gaze pointing (accessibility), foot controls, …
- Sensors in mobile devices (e.g. accelerometer, 3DOF), depth cameras (body input)
17
Q
Direct/Indirect Control
A
- Direct-control: pointing directly on the display
- Input space / motor space = output space
(1:1 mapping)- Touchscreen (single-touch, multi-touch)
- Passive stylus
- Active stylus (sense pressure, tilt; button
to mode switch)
- Input space / motor space = output space
- Indirect-control: input space separate from the display
- Motor space is separate from display (can
have a gain factor) - Device representation by a marker/cursor
on the display- e.g. Mouse, Touchpad, Graphics tablet
- Motor space is separate from display (can
18
Q
Absolute / Relative Input
A
- Input with indirect control devices can be classified as absolute or relative
- Absolute mapping of input: a point in motor space corresponds to a point in the display space
- e.g. Graphics tablet
- Relative mapping: input is relative to the current position in display space
- Can be performed from any position in motor space
- Mouse (cannot sense absolute position, only displacement)
- Touchpad (although it can absolute position)
19
Q
Control-display gain (CD gain)
A
- Control-display gain is a scale factor in mapping input to movement on the display:
- Example
- Mouse moves 3cm and cursor moves 3cm: CD gain = 1.
- Mouse moves 3cm and cursor moves 6cm: CD gain = 2.
- Absolute input may be scaled with a fixed CD gain
- Relative input can involve dynamic CD gain, based on a transfer function
20
Q
Transfer function
A
- The transfer function describes the mapping of input from motor space to display space
- Transfer functions for the mouse are highly
optimized and non-linear- CD gain dependent on mouse acceleration
- Increasing gain in the acceleration phase,
for gross positioning - Reducing gain when the user decelerates,
for fine positioning
21
Q
Property sensed
A
- Isotonic controllers
- Device is free moving: resistance is low and
constant - Property sensed: displacement
- Device is free moving: resistance is low and
- Isometric controllers
- Device does not move: infinite resistance
- Property sensed: force
- Elastic controllers
- Resistance increases with displacement
- Can sense displacement or force
22
Q
Order of control
A
- The property sensed by an input device can be mapped to control position or velocity
- Position control (= zero-order control)
- Input mapped to position – how far the cursor moves
- Rate control (= first-order control, or: velocity control)
- Input mapped to speed – how fast the cursor moves
23
Q
Comparison of pointing devices
A
- Touchscreens are fastest but least accurate
- Mouse consistently found to be best for both speed and accuracy
- Touchpad not as efficient but has lower acquisition time from the keyboard
- Pointing stick not as efficient for very small
movements but users can keep hands in keyboard home position - People with motor disabilities prefer joysticks or trackballs
- location of the device remains fixed (easier
reach, wheelchair mounting) - can be operated with small residual
movements
- location of the device remains fixed (easier
- Touch-sensitive devices require least force but that also increases risk of inadvertent input
24
Q
Pointing Devices - Key Points
A
- Devices can be classified by how their input is mapped
- Direct/indirect
- Absolute/relative
- Position-control/rate-control
- Transfer function and CD Gain
- All pointing devices have speed-accuracy trade-offs
- They differ in how efficient they are for different tasks
- For example, arrow keys better for nudging the cursor than the mouse,
but not for moving the cursor across the screen
