Interactive Input Methods & Graphical User Input

Interactive Input Methods & Graphical User Input

Explain the 6 logical classifications of input devices

Differentiate the 7 interactive Picture Construction Techniques

Types of input data: coordinate positions, attribute values, character-string specifications, geometric-transformation values, viewing conditions, illumination parameters,

Input procedures require interaction with display window managers & hardware devices.

Logical input device refers to input devices classified

according to data type. LOCATOR – specifies one coordinate position STROKE – specifies a set of coordinate

positions STRING – specifies text input VALUATOR – specifies a scalar value CHOICE – specifies menu selection PICK – specifies picture component selection

Devices like mouse, joystick,trackball, are used for screen-cursor position

General purpose keyboards may have 4 or 8 cursor-control keys

Light pen used for interactive input of coordinate position

graphic tablet & continuous movement of mouse, trackball, joystick are used to input a sequence of coordinate positions

primary physical device for string input is keyboard

other devices could generate character patterns that is recognized using stored dictionary of predefined patterns for specific application

valuator input is used to set scalar values for geometric transformations, viewing parameters & illumination parameters

panel of controls dials typically provides valuator input

display graphical representation of slider, buttons, rotating scales, menus

Joystick, trackball & keyboard could be adapted for valuator input by movement of the device relative to a scalar range

menus are used to select processing options, parameter values & object shapes

touch panel, keyboard & voice entry are also common choice devices

used to select part of a scene that is to be transformed or edited

using mouse, joystick or keyboard, picking the position of screen cursor to identify pixel coordinates

depending on type of object & complexity of scene, several levels of search required to identify pick object

variety of interactive methods are incorporated into graphic package as aids in construction of pictures:

1) Basic Positioning Methods interactively choose a coordinate position with

a pointing device that records the screen location

2) Dragging select an object & drag it to a new location,

thus object is then displayed in the new location.

3) Constraints procedure for altering input coordinate

values to obtain a particular orientation or alignment of an object

lines are constrained to have a particular slant

Input coordinates are constrained to lie along predefined paths

4) Grids rectangular grid displayed on screen area used

to round input coordinates to nearest grid intersection

grids facilitate object construction when need to joins new line to an existing line endpoint.

6) Rubber-Band Methods Line segments & other basic shapes constructed

& positioned using rubber-band methods to be interactively stretched or contracted

6) Gravity Field to connect lines at positions between endpoints

(that are not in grid intersections) graphic packages include procedure to convert any input position near a line segment into a position on the line using gravity field area around the line

any selected position within the gravity field of a line is “moved” to the nearest position on the line

7) Interactive Painting & Drawing Methods freehand drawing uses curves generated by

following the path of a stylus on a graphics tablet or path of the screen cursor on a video monitor

Applications include GUIs composed of display windows, icons, menus, etc to aid user in applying the software to a particular problem

consideration for user interface area: User Dialogue Windows & Icons Accommodating Multiple Skills Levels Consistency Minimizing Memorizing Backup & Error Handling Feedback