HomeworkGraphics Input Devices

Graphics Output Devices

Computer Graphics

P. Healy

CS1-08Computer Science Bldg.

tel: 202727patrick.healy@ul.ie

Spring 2019–2020

P. Healy (University of Limerick) CS4815 Spring 2019–2020 1 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

Outline

1 Homework

2 Graphics Input DevicesIntroduction

3 Graphics Output DevicesIntroductionDisplays

P. Healy (University of Limerick) CS4815 Spring 2019–2020 2 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

To Do

1 Go to Wikipedia http://en.wikipedia.org/ and read thepages on Colour Spaces(http://en.wikipedia.org/wiki/Colour_spaces), OpticalIllusions (http://en.wikipedia.org/wiki/Optical_illusion) andM. C. Escher (http://en.wikipedia.org/wiki/M._C._Escher)

2 Buy Hearn, Baker and Carithers and read all of Chapters 1and begin reading Chapter 2

3 Sort out your Linux account / password

P. Healy (University of Limerick) CS4815 Spring 2019–2020 3 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Outline

1 Homework

2 Graphics Input DevicesIntroduction

3 Graphics Output DevicesIntroductionDisplays

P. Healy (University of Limerick) CS4815 Spring 2019–2020 4 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Input Devices: Introduction

Piece of hardware by which a user enters information intoa computer system

mouse, trackball, joystick, voice systems, touch screens,others

A major goal in designing graphics software libraries isdevice-independence – enhances portability of theapplicationTo provide a level of abstraction for graphics input oroutput, most graphics systems support logical devicesThese shield the application from the details of the physicaldevices available

Physical device: a piece of hardware that provides aresponse to a stimulusAbstract this idea now to software components

P. Healy (University of Limerick) CS4815 Spring 2019–2020 5 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Logical Devices – §20.2 of HBC

Locator: to indicate a position or orientation; inputs aposition (x , y) typically via mouse or crosshairs.Pick: to select a display entity (e.g. icon); identifies adisplayed object and not just an (x , y)Valuator: to input a single “value” – maybe from a kbd or adialString: to input textChoice: to select from a set of possible actions or choicese.g. integer value from buttons on a box or via a menuselection with lightpen, crosshair or digitiser

P. Healy (University of Limerick) CS4815 Spring 2019–2020 6 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Locator Devices

Absolute or RelativeAbsolute: report position with regard to an origin e.g. datatablet, touch screenRelative: report position w.r.t. their former position e.g.mouse, joystick, Wii remote controller

Direct or IndirectDirect: user points directly at screen using light-pen orfinger on touch screen e.g. smartphone, ATM (cashmachine)Indirect: user moves cursor on screen with device not onscreen e.g. mouse or joystick, Wii remote

Discrete or ContinuousContinuous: smooth hand motion e.g. mouse, trackballDiscrete: define action e.g. cursor-control keys

P. Healy (University of Limerick) CS4815 Spring 2019–2020 7 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Virtual Reality / Voice Recognition

Virtual reality has generated a completely new set of inputdevices:

DataglovePressure padsDigitizing armVarious other tactile and gesture input device

Much research is currently in progress to devise betterways of interacting with the machineVoice recognition and natural language comprehension arealso currently the focus of much research

P. Healy (University of Limerick) CS4815 Spring 2019–2020 8 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Keyboard and Mouse

Keyboard was originalgeneral input deviceMouse was developedat SRI labs in 1963

P. Healy (University of Limerick) CS4815 Spring 2019–2020 9 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Keyboard and Mouse

Keyboard was originalgeneral input deviceMouse was developedat SRI labs in 1963

P. Healy (University of Limerick) CS4815 Spring 2019–2020 9 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Keyboard and Mouse

Keyboard was originalgeneral input deviceMouse was developedat SRI labs in 1963

P. Healy (University of Limerick) CS4815 Spring 2019–2020 9 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Graphics Tablet

Artist’s toolVery fine resolution, very precisemeasurementsPopular in East Asia as device forentering CJK (Chinese, Japanese,Korean) charactersReplacement for the computermouse as a pointing device??

P. Healy (University of Limerick) CS4815 Spring 2019–2020 10 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Graphics Tablet

Artist’s toolVery fine resolution, very precisemeasurementsPopular in East Asia as device forentering CJK (Chinese, Japanese,Korean) charactersReplacement for the computermouse as a pointing device??

P. Healy (University of Limerick) CS4815 Spring 2019–2020 10 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Digital Camera

Raster (line-by-line) ScanMatrix of charge-coupled device (CCD) or complementarymetal-oxide semiconductor (CMOS) light sensorsSensors produce digital output proportional to lightintensity of each of colour bandsGood light sensitivity, resolutionMonochrome, colour, smart (framegrabber for machinevision applications)

P. Healy (University of Limerick) CS4815 Spring 2019–2020 11 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Digital Scanner

Line sensor moves over the imageVery high resolutionColour sensitive

P. Healy (University of Limerick) CS4815 Spring 2019–2020 12 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Laser Scanner

Sweeps scene with laser beamUses “radar” technology to detectdistancesBuilds 3D surface representation ofobject from point cloudNo colour!

P. Healy (University of Limerick) CS4815 Spring 2019–2020 13 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

Laser Scanner

Sweeps scene with laser beamUses “radar” technology to detectdistancesBuilds 3D surface representation ofobject from point cloudNo colour!

P. Healy (University of Limerick) CS4815 Spring 2019–2020 13 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

CT Scanner

Computed tomography (prev.Computed Axial Tomography)Captures a series of 2D X-rays andis combined by computer into a 3Ddensity matrix (volumetric rendering)

P. Healy (University of Limerick) CS4815 Spring 2019–2020 14 / 22

HomeworkGraphics Input Devices

Graphics Output DevicesIntroduction

CT Scanner

Computed tomography (prev.Computed Axial Tomography)Captures a series of 2D X-rays andis combined by computer into a 3Ddensity matrix (volumetric rendering)

P. Healy (University of Limerick) CS4815 Spring 2019–2020 14 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Outline

1 Homework

2 Graphics Input DevicesIntroduction

3 Graphics Output DevicesIntroductionDisplays

P. Healy (University of Limerick) CS4815 Spring 2019–2020 15 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Types of Output Device

Cathode Ray Tube (CRT)TFT (Thin Film Transistor) LiquidCrystal DisplayPrinterProjectorVirtual Reality Headset e.g., GoogleCardboarde-PaperHolographic DomeVirtual retinal display (VRD) (or,retinal scan display)Blinkenlights

P. Healy (University of Limerick) CS4815 Spring 2019–2020 16 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Types of Output Device

Cathode Ray Tube (CRT)TFT (Thin Film Transistor) LiquidCrystal DisplayPrinterProjectorVirtual Reality Headset e.g., GoogleCardboarde-PaperHolographic DomeVirtual retinal display (VRD) (or,retinal scan display)Blinkenlights

P. Healy (University of Limerick) CS4815 Spring 2019–2020 16 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Outline

1 Homework

2 Graphics Input DevicesIntroduction

3 Graphics Output DevicesIntroductionDisplays

P. Healy (University of Limerick) CS4815 Spring 2019–2020 17 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Cathode Ray Tube

Horizontal and verticaldeflectors focus anelectron beam emitted byan electron gun on anyspot on a phosphor coatedscreen

Maximum number of points, or pixels that can be displayedwithout overlap is called the resolution, e.g. 1280 x 1024 or1024 x 768Three types of phospho(u)r on screen: RGB; three elec.guns needed, one for each colourDue to decay of light, need to refresh screen (60 - 120 Hz)Continuity lost at refresh rates below 24Hz (jerkiness)

P. Healy (University of Limerick) CS4815 Spring 2019–2020 18 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Raster Scan Displays

Treat screen as matrix of pixels andcombine combinations of pixels tocreate characters, lines, shapes, etc.Electron gun fires electrons at screenrow by rowInterlacing trick when refresh rates areslow

Interlacing demo in context of png files

HD TV: 1920x1080 pixels;UHD “4K” TV: 3,840x2,160 (=8M) pixels

See also How a Television works 1

1With thanks to Cathal Foley.P. Healy (University of Limerick) CS4815 Spring 2019–2020 19 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Raster Scan Displays (contd.)

Screen is “controlled” by frame buffer, a matrix datastructure comprising information to be displayedEach pixel’s colour, intensity are stored in frame bufferUsing 24 bits for each pixel (8 bits for each colour)→ 28 × 28 × 28 = 16,777,216 colours in total24 bits / pixel with a 1024 x 1024 display: 1024 x 1024 x 3bytes = 3 Mb (megabytes)

P. Healy (University of Limerick) CS4815 Spring 2019–2020 20 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Random Scan (Vector) Displays

Draws exact lines, rather than series ofdots that approximate themUsed quite a bit for plotters (X − Yplotters)Random scan displays not used muchany moreAside: pictures stored using vectors aremore space efficient and scale muchbetter; picture to left is detail of acamera; (b) is vector-basedenlargement, (c) is raster-basedenlargement

SVG example Euro Sign: SVG

P. Healy (University of Limerick) CS4815 Spring 2019–2020 21 / 22

HomeworkGraphics Input Devices

Graphics Output Devices

IntroductionDisplays

Flat Panel Displays

Plasma panels (emissive) (see wp:Plasma)TFT / LCD (nonemissive) (see wp:TFT and TFT monitor)

P. Healy (University of Limerick) CS4815 Spring 2019–2020 22 / 22