CS-321 Dr. Mark L. Hornick 1 Graphics Display Hardware Display technologies CRT LCD Storage tube Drawing methods Vector Raster Architecture

CS-321 Dr. Mark L. Hornick 2 Sketchpad MIT Light pen Powered by “Whirlwind”, MIT’s prototype of the 1 st interactive computer Req’d high bandwidth Vector display Monochromatic

CS-321 Dr. Mark L. Hornick 3 “Modern” Cathode Ray Tube (CRT) Quasi-spherical screen Phosphorescence period = 1/30 s to 1/60 s

CS-321 Dr. Mark L. Hornick 4 CRT – Sony Trinitron Slotted shadow mask Curvilinear screen Larger holes -- brighter image

CS-321 Dr. Mark L. Hornick 5 Vector Scanning Electron beam can be arbitrarily directed Number of displayable vectors is finite Non-standard drive electronics

CS-321 Dr. Mark L. Hornick baud serial Begin COLOR(a) MOVE(ix,iy) DRAW(ix,iy) COLOR(b) DRAW(…) End Early hi-performance displays Minicomputer Display Processor

CS-321 Dr. Mark L. Hornick 7

8 Tektronix Vector Display T x 512 ~$8,000 T x 3172 ~$18,000 Persistent Storage Phosphor No digital memory

CS-321 Dr. Mark L. Hornick 9 Direct View Storage Tube Two electron guns Primary electron gun draws the picture by knocking out electrons from the storage grid, producing a positively charged pattern. Low speed electrons from the flood gun are attracted to the storage grid, and pass through the positively charge pattern spots (past the collector grid) to hit the screen. Once a picture is drawn it stays until erased by putting a charge over all of the storage grid so that the electrons hit all of the screen (producing a green flash on a green screen monitor). Much cheaper then a regular random scan system did not require a built in CPU host computer was used to draw the image once

CS-321 Dr. Mark L. Hornick baud serial MOVE(ix,iy) DRAW(ix,iy) POINT(ix,iy) DASH(ix,iy,idash)

CS-321 Dr. Mark L. Hornick 11 Circa 1981

CS-321 Dr. Mark L. Hornick 12 Raster Scanning

CS-321 Dr. Mark L. Hornick 13 Video Display Video graphics adapter Television monitor

CS-321 Dr. Mark L. Hornick 14 Early graphics adapters Bus CPU System Memory Scan Converter video, vga Frame buffer Pixel construction CPU constructs “virtual image” in System Memory Scan converter reads virtual image and converts to video or vga signals