INPUT DEVICES

                                          Various devices are available for data input on graphics workstations. Most systems have a keyboard and one or more additional devices specially designed for interactive input. These include a mouse, trackball, spaceball, joystick, digitizers, dials, and button boxes. another input devices utilized in particular applications are data gloves, touch panels, image scanners, and voice systems.

Keyboards

An alphanumeric keyboard on a graphics system is employed primarily as a tool for entering text strings. The keyboard is an efficient device for inputting such no graphic data as picture labels related to a graphics display. Keyboards can even be given features to facilitate entry of screen coordinates, menu selections, or graphics functions.

Cursor control keys and performance keys are common features on general purpose keyboards. Function keys allow users to enter frequently used operations during a single keystroke, and cursor-control keys is wont to select displayed objects or coordinate positions by positioning the screen cursor. Other sorts of cursor positioning devices, like a trackball or joystick, are included on some keyboards. Additionally, a numeric keypad is usually included on the key board for fast entry of numeric data.

For specialized applications, input to a graphics application may come from a group of buttons, dials, or switches that select data values or customized graphics operations. Buttons and switches are often wont to input predefined functions, and dials are common devices for entering scalar values. Real numbers within some defined range are selected for input with dial rotations. Potentiometers are wont to measure dial rotations, which are then converted to deflection voltages for cursor movement.

Mouse

A mouse is little hand-held box wont to position the screen cursor. Wheels or rollers on the underside of the mouse is wont to record the number and direction of movement. Another method for detecting mouse motion is with an optical sensor. For these systems, the mouse is moved over a special mouse pad that incorporates a grid of horizontal and vertical lines. The optical sensor detects movement across the lines within the grid. Since a mouse is picked up and put down at another position without change in cursor movement, it's used for creating relative changes within the position of the screen cursor. One, two, or three buttons are usually included on the highest of the mouse for signaling the execution of some operation, like recording cursor position or invoking a function. Mast general-purpose graphics systems now include a mouse and a keyboard because the major input devices. Additional devices is included within the basic mouse design to extend the quantity of allowable input parameters.


Three buttons, a thumbwheel on the side, a trackball on the highest, and a typical mouse ball underneath. This design provides six degrees of freedom to pick spatial positions, rotations, and other parameters. With the Z mouse, we are able to obtain an object, rotate it, and move it in any direction, or we are able to navigate our viewing position and orientation through a 3 dimensional scene. Applications of the Z mouse include computer game, CAD, and animation. 

Trackball and Spaceball

As the name implies, a trackball could be a ball that may be rotated with the fingers or palm of the hand, it produce screen-cursor movement. Potentiometers, attached to the ball, measure the number and direction of rotation. Trackballs are often mounted on keyboards or other devices like the Z mouse. While a trackball could be a two-dimensional positioning device, a spaceball provides six degrees of freedom. Unlike the trackball, a spaceball doesn't actually move. Strain gauges measure the number of pressure applied to the spaceball to supply input for spatial positioning and orientation because the ball is pushed or pulled in various directions. Spaceball are used for three-dimensional positioning and selection operations in virtual-reality systems, modeling, animation, CAD, and other applications.

 
Joysticks

A joystick consists of a little, vertical lever (called the stick) mounted on a base that's wont to steer the screen cursor around. Most joysticks select screen positions with actual stick movement; others reply to pressure on the stick. Some joysticks are mounted on a keyboard; others function as stand-alone units. the gap that the stick is moved in any direction from its center position corresponds to screen-cursor movement therein direction. Potentiometers mounted at the bottom of the joystick measure the number of movement, and is derived return the follow the middle position when it's released. One or more buttons is programmed to act as input switches to signal certain actions once a screen position has been selected.

In another variety of movable joystick, the stick is employed to activate switches that cause the screen cursor to maneuver at a relentless rate within the direction selected. Eight switches, arranged during a circle, are sometimes provided, so the stick can select anyone of eight directions for cursor movement. Pressure sensitive joy- sticks, also called isometric joysticks, have a no movable stick. Pressure on the stick is measured with strain gauges and converted to movement of the cursor within the direction specified.
 

Data Glove

A data glove that may be wont to grasp a "virtual" object, the glove is built with a series of sensors that detect hand and finger motions. Electromagnetic coupling between transmitting antennas and receiving antennas is employed to supply information about the position and orientation of the hand. The transmitting and receiving antennas can each be structured as a group of three mutually perpendicular coils, forming a three-dimensional coordinate system. Input from the glove is wont to position or manipulate objects during a virtual scene. A two-dimensional projection of the scene is viewed on a video monitor, or a three-dimensional projection is viewed with a headset.