Input/Output Devices Graphical Interface Systems Dr. M. Al-Mulhem Feb. 1, 2008

Display Devices Vector display –Draws only lines –Also known as random scan Raster display –Discrete grid of elements (frame buffers pixels) –Shapes drawn by setting the “right” elements –Frame buffer scanned (one line at a time) to preserve image –on CRT LCD – liquid crystal display –Polarizing light –Crystals react to current

Vector vs. Raster Vector –Easy to draw lines –Can display only lines –Refresh time depends on scene complexity –Old fashioned – Very uncommon today Raster –Hard to draw smooth lines –Displays a discrete approximation of any shape –Refresh the entire frame buffer –Used practically everywhere

Terminology Pixel: Picture element –Smallest accessible element in a picture –Usually rectangular or circular Aspect Ratio: –Ratio between physical dimensions of a pixel (not necessarily 1) Dynamic Range: –Ratio between minimal and maximal light intensity emitted by display pixel.

Terminology (cont). Resolution: The maximum number of pixels that can be displayed without overlap on the screen. 1024×768 pixels Screen Space: A discrete 2D Cartesian coordinate system of the screen pixels. Object Space: The 3D Cartesian coordinate system of the universe.

Hardcopy Devices Plotter Dot Matrix Printer: Laser Printer:

Color Printing Technologies Ink Jet –Sprays microscopic dots of ink through small holes to form dots on paper. Thermal Wax –Creates colors by melting and bonding color wax dots onto special paper. Dye Sublimation –Creates continuous-tone by heating dyes until they turn into gas (sublimate), that fuses into the paper. Film Recorder –A camera in front of a designated B&W CRT. RGB channels are sent one at a time through an appropriate filter.

Standard Input Devices Keyboard –For alphanumeric input. Mouse/Trackball –Provides relative movement information.

2D Input Devices Joystick –Provides relative movement information. Digitizer/Tablet –Provides absolute position information. Touch Screen –A CRT screen that can sense pressure on its surface. Light Pen –Synchronized with the CRT scan, it can locate a position on screen.

3D Input Devices Dataglove –Sensors to detect hand and finger motions –Used to grasp a virtual objec.t Head mounted Display –Used to interact with the environment. Space Ball –Position and orientation is measured by the pressure applied to the ball.

Image Capture Digital Cameras –High resolutions. Video Camera –Low resolution. Scanner –High resolution.

More Image Capture Devices Thermal imaging –Non visible images Ultrasound –High frequency sound waves are converted to form an image.

3D Scanners CT / MRI –3D Imaging 3D Range Scanner –Geometry and color texture digitizer