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COMPUTERGRAPHICS(XCS354)TwoMarkQuestion
UNITI
1.DefineComputergraphics.Computergraphicsremainsoneofthemostexistingandrapidlygrowingcomputerfields.Computergraphicsmaybedefinedasapictorialrepresentationorgraphicalrepresentationofobjectsinacomputer.
2.Whatismeantbyscancode?Whenakeyispressedonthekeyboard,thekeyboardcontrollerplacesacodecarrytothekeypressedintoapartofthememorycalledasthekeyboardbuffer.Thiscodeiscalledasthescancode.
3.Whatismeantbyrefreshingofthescreen?Somemethodisneededformaintainingthepictureonthescreen.Refreshingofscreenisdonebykeepingthephosphorusglowingtoredrawthepicturerepeatedly.(i.e.)Byquicklydirectingtheelectronicbeambacktothesamepoints.
4.DefineRandomscan/Rasterscandisplays?Randomscanisamethodinwhichthedisplayismadebytheelectronicbeamwhichisdirectedonlytothepointsorpartofthescreenwherethepictureistobedrawn.
TheRasterscansystemisascanningtechniqueinwhichtheelectronssweepfromtoptobottomandfromlefttoright.Theintensityisturnedonorofftolightandunlightthepixel.
5.ListoutthemeritsanddemeritsofPenetrationtechniques?ThemeritsanddemeritsofthePenetrationtechniquesareasfollows
ItisaninexpensivetechniqueIthasonlyfourcolorsThequalityofthepictureisnotgoodwhenitiscomparedtoothertechniquesItcandisplaycolorscansinmonitorsPoorlimitationetc.6.ListoutthemeritsanddemeritsofDVST?
Themeritsanddemeritsofdirectviewstoragetubes[DVST]areasfollows
IthasaflatscreenRefreshingofscreenisnotrequiredSelectiveorparterasingofscreenisnotpossibleIthaspoorcontrast
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PerformanceisinferiortotherefreshCRT.
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7.Whatdoyoumeanbyemissiveandnon-emissivedisplays?Theemissivedisplayconvertselectricalenergyintolightenergy.Theplasmapanels,thinfilmelectro-luminescentdisplaysaretheexamples.
TheNonemissiveareopticaleffectstoconvertthesunlightorlightfromanyothersourcetographicform.Liquidcrystaldisplayisanexample.
8.ListoutthemeritsanddemeritsofPlasmapaneldisplay?MeritsRefreshingisnotrequiredProduceaverysteadyimagefreeofFlickerLessbulkythanaCRT.DemeritsPoorresolutionofupto60d.p.iItrequirescomplexaddressingandwiringItiscostlierthanCRT.9.Whatispersistence?
Thetimeittakestheemittedlightfromthescreentodecayonetenthofitsoriginalintensityiscalledaspersistence.
10.Whatisresolution?ThemaximumnumberofpointsthatcanbedisplayedwithoutanoverlaponaCRTiscalledasresolution.
11.WhatisAspectratio?TheratioofverticalpointstothehorizontalpointsnecessarytoproducelengthoflinesinbothdirectionsofthescreeniscalledtheAspectratio.Usuallytheaspectratiois.
12.WhatismeantbyAddressability?TheAddressabilityisthenumberofindividualdotsperinch(d.p.i)thatcanbecreated.Iftheaddressofthecurrentdotis(x,y)thenthenextdotwillbe(x+y),(x+y+1)etc.
13.Whatisadotsize?Dotsizemaybedefinedasthediameterofasingledotonthedevicesoutput.DotsizeisalsocalledastheSpotsize.
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14.Whatisinterdotdistance?Interdotdistanceisthereciprocalofaddressability.Iftheaddressabilityislarge,theinterdotdistancewillbeless.Theinterdotdistanceshouldbelesstogetsmoothshapes.
15.Whatisthedifferencebetweenimpactandnon-impactprinters?Impactprinterpressformedcharacterfacesagainstaninkedribbonontothepaper.Alineprinteranddot-matrixprinterareexamples.
Non-impactprinterandplottersuseLasertechniques,inkjetsprays,Xerographicprocess,electrostaticmethodsandelectrothermalmethodstogetimagesontothepapers.Examplesare:Inkjet/Laserprinters.
16.WhatarethefeaturesofInkjetprinters?Theycanprint2to4pages/minutes.Resolutionisabout360d.p.i.Thereforebetterprintqualityisachieved.
Theoperatingcostisverylow.Theonlypartthatrequiresreplacementisinkcartridge.4colorscyane,yellow,majenta,blackareavailable.17.WhataretheadvantagesoflaserprinterHighspeed,precisionandeconomy.Cheaptomaintain.Qualityprinters.Lastsforlongertime.
Tonerpowerisverycheap.18.Whataretheadvantagesofelectrostaticplotters?Theyarefasterthanpenplottersandveryhighqualityprinters.Recentelectrostaticplottersincludeascan-conversioncapability.Colorelectrostaticplottersareavailable.Theymakemultiplepassesoverthepapertoplotcolorpictures.19.Definepixel?Pixelisshortenedformsofpictureelement.Eachscreenpointisreferredtoas
pixelorpel.
20.Whatisframebuffer?Picturedefinitionisstoredinamemoryareacalledframebufferorrefreshbuffer.
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21.Whatisbitmapandwhatispixmap?Theframebufferusedintheblackandwhitesystemisknownasbitmapwhichtakeonebitperpixel.Forsystemswithmultiplebitsperpixel,theframebufferisoftenreferredtoasapixmap.
22.WhatisaVectordisplayorstrokewritingorcalligraphicdisplay?Randomscanmonitorsdrawapictureonelineatatimeandforthisreasonarealsoreferredasvectordisplays.
23.Wherethevideocontrollerisused?Aspecialpurposeprocessor,whichisusedtocontroltheoperationofthedisplaydevice,isknownasvideocontrollerordisplaycontroller.
24.Whatdoyoumeanbyscanconversion?Amajortaskofthedisplayprocessorisdigitizingapicturedefinitiongiveninanapplicationprogramintoasetofpixel-intensityvaluesforstorageintheframebuffer.Thisdigitizationprocessiscalledscanconversion.
25.Whatisrunlengthencoding?
Runlengthencodingisacompressiontechniqueusedtostoretheintensityvaluesintheframebuffer,whichstoreseachscanlineasasetofintegerpairs.Onenumbereachpairindicatesanintensityvalue,andsecondnumberspecifiesthenumberofadjacentpixelsonthescanlinethataretohavethatintensityvalue
UNITII
1.Whatisanoutputprimitive?Graphicsprogrammingpackagesprovidefunctiontodescribeasceneintermsofthesebasicgeometricstructures,referredtoasoutputprimitives.
2.Whatdoyoumeanbyjaggies?Linewithstairstepappearanceisknownasjaggies.3.Whatispointinthecomputergraphicssystem?Thepointisamostbasicgraphicalelement&iscompletelydefinedbyapairofusercoordinates(x,y).
4.Writeshortnotesonlines?Alineisofinfiniteextentcanbedefinedbyanangleofslope.andonepointonthelineP=P(x,y).ThiscanalsobedefinedasY=mx+CwhereCistheY-intercep
t.
5.DefineCircle?Circleisdefinedbyitscenterxc,ycanditsradiusinusercoordinateunits.Theequationofthecircleis(x-xc)+(y-yc)=r2.
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6.DefineEllipse?Anellipsecanusethesameparametersxc,yc,rasacircle,inadditiontotheeccentricitye.theeqnofanellipseis:(x-xc)2/a2+(y-yc)2/b2=1
7.Definepolygon?Apolygonisanyclosedcontinuessequenceoflinesegmentsie,apolylinewhoselastnodepointissameasthatofitsfirstnodepoint.Thelinesegmentsformthesidesofthepolygonandtheirintersectingpointsformtheverticesofthepolygon.
8.Distinguishbetweenconvexandconcavepolygons?Ifthelinejoininganytwopointsinthepolygonliescompletelyinsidethepolygonthen,theyareknownasconvexpolygons.Ifthelinejoininganytwopointsinthepolygonliesoutsidethepolygonthen,theyareknownasconcavepolygons.
9.Whatisseedfill?Onewaytofillapolygonistostartfromagivenpoint(seed)knowntobeinside
thepolygonandhighlightoutwardfromthispointi.eneighboringpixelsuntilencountertheboundarypixels,thisapproachiscalledseedfill.
10.Whatisscanlinealgorithm?Onewaytofillthepolygonistoapplytheinsidetest.i.etocheckwhetherthepixelisinsidethepolygonoroutsidethepolygonandthenhighlightthepixelwhichlieinsidethepolygon.Thisapproachisknownasscan-linealgorithm.
11.Definecoherenceproperties?Acoherencepropertyofasceneisapartofascenebywhichrelateonepartof
thescenewiththeotherpartsofthescene.
12.Whatisanactiveedgelistinthescanlinealgorithm?Theactiveedgelistforascanlinecontainsalledgescrossedbythatscanline.13.Whatisawindingnumber?Windingnumbermethodisusedtocheckwhetheragivenpointisinsideoroutsidethepolygon.Inthismethodgiveadirectionnumbertoalltheedgeswhichcrossthescanline.Iftheedgestartsbelowthelineandendsabovescanlinegivedirectionas-1.otherwise1.Frpolygonsortwodimensionalobjects,thepointissaidtobeinsi
dewhenthevalueofwindingnumberisnonzero.
14.Whatiscellarray?Thecellarrayisaprimitivethatallowsuserstodisplayanarbitraryshapedefinedasatwodimensionalgridpattern.
15.Whatistypeface?Letters,numbersandothercharacterscanbedisplayedinavarietyofsizesand
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styles.Theoveralldesignstyleforasetofcharactersiscalledatypeface.
16.Whatdoyoumeanbyfont?Thetermfontreferredtoasetofcastmetalcharacterformsinaparticularsizeandformat,suchas10-pointcourieritalic.
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17.Whatisabitmappedfont?Asimplemethodforrepresentingthecharactershapesinaparticulartypefaceistouserectangulargridpatterns.Thesetofcharactersarethenreferredtoasabitmapfont.
18.Whatisanoutlinefont?Aflexibleschemeistodescribecharactershapesusingstraight-lineandcurvesections.Inthiscase,thesetofcharacteriscalledanoutlinefont.
19.Whatisanattributeparameter?Anyparameterthataffectsthewayaprimitiveistobedisplayedisreferredtoasanattributeparameter.
20.Whatarethevariousattributesofaline?Thelinetype,widthandcoloraretheattributesoftheline.Thelinetypeincludesolidline,dashedlines,anddottedlines.
21.Whatispixelmask?Pixelmaskisastringcontainingthedigits1and0toindicatewhichpositionsto
plotalongthelinepath.Themask1111000,couldbeusedtodisplayadashedlinewithadashlengthof4andinterdotspacingofthree.
22.WhatisaLinecap?Linecapscanbeusedtoadjusttheshapeofthelineendstogiveabetterappearance.Therearethreetypesoflinecaps.Buttcapwhichhasasquareend,roundcapwhichhasasemicircleend,projectingsquarecapwhichhasonehalfofthelinewidthbeyondthespecifiedendpoints.
23.Listoutthemethodsusedforsmoothlyjoiningtwolinesegments?
.Mitterjoin-byextendingtheouterboundariesofeachofthetwolinesuntiltheymeet..Roundjoinbycappingtheconnectionbetweenthetwosegmentswithacircularboundarywhosediameterisequaltothelinewidth..Beveljoinbydisplayingthelinesegmentswithbuttcapsandfillinginthetriangulargapwherethesegmentmeet.24.WhatisColorLookuptable?Incolordisplays,24bitsperpixelarecommonlyused,where8bitsrepresent256levelforeachcolor.Itisnecessarytoread24-bitforeachpixelfromframeb
uffer.Thisisverytimeconsuming.ToavoidthisvideocontrolleruseslookuptabletostoremanyentriestopixelvaluesinRGBformat.Thislookuptableiscommonlyknownascolourtable.
25.Whatistilingpatterns?Theprocessoffillinganareawithrectangularpatterniscalledtilingandrectangularfillpatternsaresometimesreferredtoastilingpatterns.
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26.Whatissoftfill?Softfillisafillingmethodinwhichfillcoloriscombinedwiththebackgroundcolors.
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27.Whatiskernedcharacter?Thecharacterswhichextendbeyondthecharacterbodylimitsisknownaskernedcharacter.Examplefandj.
28.Whatischaracterupvector?Theorientationforadisplayedcharacterstringissetaccordingtothedirectionofthecharacterupvector.
29.Definebundledattributes?Individualattributecommandsprovideasimpleanddirectmethodforspecifyingattributeswhenasingleoutputdeviceisused.Whenseveralkindsofoutputdeviceareavailableatagraphicsinstallation,itisconvenienttosetupatableforeachoutputdevicethatlistssetofattributevaluesthataretobeusedonthatdevicetodisplayeachprimitivetype.Attributespecifiedinthismannerisknownasbundledattribute.
30.Whatisaliasing?Inthelinedrawingalgorithms,allrasterzedlocationsdonotmatchwiththetruelineandhavetorepresentastraightline.Thisproblemissevereinlowresolu
tionscreens.Insuchscreenslineappearslikeastair-step.Thiseffectisknownasaliasing.
31.Whatisantialiasing?Theprocessofadjustingintensitiesofthepixelsalongthelinetominimizetheeffectofaliasingiscalledantialiasing.
32.Whatispixelphasing?Pixelphasingisanantialiasingtechnique,stairstepsaresmoothedoutbymovingtheelectronbeamtomorenearlyapproximatepositionsspecifiedbytheobjectg
eometry.
UNITIII
1.WhatisTransformation?Transformationistheprocessofintroducingchangesintheshapesizeandorientationoftheobjectusingscalingrotationreflectionshearing&translationetc.
2.Writeshortnotesonactiveandpassivetransformations?|
Intheactivetransformationthepointsxandxrepresentdifferentcoordinatesofthesamecoordinatesystem.Hereallthepointsareacteduponbythesametransformationandhencetheshapeoftheobjectisnotdistorted.Inapassive
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transformationthepointsxandxrepresentsamepointsinthespacebutinadifferentcoordinatesystem.Herethechangeinthecoordinatesismerelyduetothechang
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einthetypeoftheusercoordinatesystem.
3.Whatistranslation?Translationistheprocessofchangingthepositionofanobjectinastraight-linepathfromonecoordinatelocationtoanother.Everypoint(x,y)intheobjectmust
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undergoadisplacementto(x,y).thetransformationis:
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x=x+tx;y=y+ty
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4.Whatisrotation?A2-Drotationisdonebyrepositioningthecoordinatesalongacircularpath,in|
thex-yplanebymakingananglewiththeaxes.Thetransformationisgivenby:X=r
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cos(q+f)andY=rsin(q+f).
5.Whatisscaling?Thescalingtransformationschangestheshapeofanobjectandcanbecarriedoutbymultiplyingeachvertex(x,y)byscalingfactorSx,SywhereSxisthescalingfactorofxandSyisthescalingfactorofy.
6.Whatisshearing?TheshearingtransformationactuallyslantstheobjectalongtheXdirectionortheYdirectionasrequired.ie;thistransformationslantstheshapeofanobjectal
ongarequiredplane.
7.Whatisreflection?Thereflectionisactuallythetransformationthatproducesamirrorimageofanobject.Forthisusesomeanglesandlinesofreflection.
8.Distinguishbetweenwindowport&viewport?Aportionofapicturethatistobedisplayedbyawindowisknownaswindowport.Thedisplayareaofthepartselectedortheforminwhichtheselectedpartisviewedisknownasviewport.
9.Defineclipping?Clippingisthemethodofcuttingagraphicsdisplaytoneatlyfitapredefinedgraphicsregionortheviewport.
10.Whatiscovering(exteriorclipping)?Thisisjustoppositetoclipping.Thisremovesthelinescominginsidethewindowsanddisplaystheremaining.Coveringismainlyusedtomakelabelsonthecomplexpictures.
11.Whatistheneedofhomogeneouscoordinates?Toperformmorethanonetransformationatatime,usehomogeneouscoordinates
ormatrixes.Theyreduceunwantedcalculationsintermediatestepssavestimeandmemoryandproduceasequenceoftransformations.
12.Distinguishbetweenuniformscalinganddifferentialscaling?Whenthescalingfactorssxandsyareassignedtothesamevalue,auniformscalingisproducedthatmaintainsrelativeobjectproportions.Unequalvaluesforsxandsyresultinadifferentialscalingthatisoftenusedindesignapplication.
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13.Whatisfixedpointscaling?Thelocationofascaledobjectcanbecontrolledbyapositioncalledthefixedpointthatistoremainunchangedafterthescalingtransformation.
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14.DefineAffinetransformation?AcoordinatetransformationoftheformX=axxx+axyy+bx,yayxx+ayyy+byiscalledatwo-dimensionalaffinetransformation.Eachofthetransformedcoordinatesxandyisalinearfunctionoftheoriginalcoordinatesxandy,andparametersaijandbkareconstantsdeterminedbythetransformationtype.
15.DistinguishbetweenbitBltandpixBlt?Rasterfunctionsthatmanipulaterectangularpixelarraysaregenerallyreferredtoasrasterops.Movingablockofpixelsfromonelocationtoanotherisalsocalledablocktransferofpixelvalues.Onabilevelsystem,thisoperationiscalledabitBlt(bit-blocktransfer),onmultilevelsystemtiscalledpixBlt.
16.ListoutthevariousTextclipping?.All-or-nonestringclipping-ifallofthestringisinsideaclipwindow,keepit
otherwisediscards..All-or-nonecharacterclippingdiscardonlythosecharactersthatarenotcompletelyinsidethewindow.Anycharacterthateitheroverlapsorisoutsideawindowboundaryisclipped..Individualcharactersifanindividualcharacteroverlapsaclipwindowboundary,clipoffthepartsofthecharacterthatareoutsidethewindow.UNITIV
1.Whatarethevariousrepresentationschemesusedinthreedimensionalobjects?
.Boundaryrepresentation(B-res)describethe3dimensionalobjectasasetofsurfacesthatseparatetheobjectinteriorfromtheenvironment..Space-portioningrepresentationdescribeinteriorproperties,bypartitioningthespatialregioncontaininganobjectintoasetofsmall,nooverlapping,contiguoussolids.2.WhatisPolygonmesh?Polygonmeshisamethodtorepresentthepolygon,whentheobjectsurfacesaretiled,itismoreconvenienttospecifythesurfacefacetswithameshfunction.
Thevariousmeshesare
Trianglestrip(n-2)connectedtrianglesQuadrilateralmeshgenerates(n-1)(m-1)Quadrilateral
3.WhatisBezierBasisFunction?BezierBasisfunctionsareasetofpolynomials,whichcanbeusedinsteadofthe
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primitivepolynomialbasis,andhavesomeusefulpropertiesforinteractivecurvedesign.
4.Whatissurfacepatch?Asinglesurfaceelementcanbedefinedasthesurfacetracedoutastwoparameters(u,v)takeallpossiblevaluesbetween0and1inatwo-parameterrepresentation.Suchasinglesurfaceelementisknownasasurfacepatch.
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5.Writeshortnotesonrenderingbi-cubicsurfacepatchesofconstantuandvmethod?Thesimplewayistodrawtheiso-parmetriclinesofthesurface.Discreteapproximationstocurvesonthesurfaceareproducedbyholdingoneparameterconstantandallowingtheothertovaryatdiscreteintervalsoveritswholerange.Thisproducecurvesofconstantuandconstantv.
6.Whataretheadvantagesofrenderingpolygonsbyscanlinemethod?i.Themaxandminvaluesofthescanwereeasilyfound.ii.Theintersectionofscanlineswithedgesiseasilycalculatedbyasimpleincrementalmethod.iii.Thedepthofthepolygonateachpixeliseasilycalculatedbyanincrementalmethod.7.Whataretheadvantagesofrenderingbypatchsplitting?i.Itisfast-especiallyonworkstationswithahardwarepolygon-renderingpipeline.ii.
Itsspeedcanbevariedbyalteringthedepthofsub-division.8.DefineB-Splinecurve?AB-Splinecurveisasetofpiecewise(usuallycubic)polynomialsegmentsthatpassclosetoasetofcontrolpoints.Howeverthecurvedoesnotpassthroughthesecontrolpoints,itonlypassesclosetothem.
9.Whatisaspline?Toproduceasmoothcurvethroughadesignedsetofpoints,aflexiblestripcalledsplineisused.Suchasplinecurvecanbemathematicallydescribedwithapiecewisecubicpolynomialfunctionwhosefirstandsecondderivativesarecontinuousacro
ssvariouscurvesection.
10.Whatistheuseofcontrolpoints?Splinecurvecanbespecifiedbygivingasetofcoordinatepositionscalledcontrolpoints,whichindicatesthegeneralshapeofthecurve,canspecifysplinecurve.
11.Whatarethedifferentwaysofspecifyingsplinecurve?Usingasetofboundaryconditionsthatareimposedonthespline.
UsingthestatematrixthatcharacteristicsthesplineUsingasetofblendingfunctionsthatcalculatethepositionsalongthecurvepathbyspecifyingcombinationofgeometricconstraintsonthecurve12.WhataretheimportantpropertiesofBezierCurve?ItneedsonlyfourcontrolpointsItalwayspassesthroughthefirstandlastcontrolpoints
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Thecurveliesentirelywithintheconvexhalfformedbyfourcontrolpoints.
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13.Differentiatebetweeninterpolationsplineandapproximationspline?Whenthesplinecurvepassesthroughallthecontrolpointsthenitiscalledinterpolate.Whenthecurveisnotpassingthroughallthecontrolpointsthenthatcurveiscalledapproximationspline.
14.Whatdoyoumeanbyparabolicsplines?Forparabolicsplinesaparabolaisfittedthroughthefirstthreepointsp1,p2,p3ofthedataarrayofkotpoints.Thenasecondparabolicarcisfoundtofitthesequenceofpointsp2,p3,p4.Thiscontinuesinthiswayuntilaparabolicarcisfoundtofitthroughpointspn-2,pn-1andpn.Thefinalplottedcurveisameshingtogetherofalltheseparabolicarcs.
15.Whatiscubicspline?Cubicsplinesareastraightforwardextensionoftheconceptsunderlyingparabolicspline.Thetotalcurveinthiscaseisasequenceofarcsofcubicratherthanparaboliccurves
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Eachcubicsatisfies:ax+bx+cx+d
16.WhatisaBlobbyobject?Someobjectsdonotmaintainafixedshape,butchangetheirsurfacecharacteristicsincertainmotionsorwheninproximitytootherobjects.Thatisknownasblobbyobjects.Examplemolecularstructures,waterdroplets.
17.DefineOctrees?Hierarchicaltreestructurescalledoctrees,areusedtorepresentsolidobjectsin
somegraphicssystems.Medicalimagingandotherapplicationsthatrequiredisplaysofobjectcrosssectionscommonlyuseoctreerepresentation.
18.DefineProjection?Theprocessofdisplaying3Dintoa2Ddisplayunitisknownasprojection.Theprojectiontransforms3Dobjectsintoa2Dprojectionplane.
19.Whatarethestepsinvolvedin3Dtransformation?ModelingTransformationViewingTransformation
ProjectionTransformationWorkstationTransformation20.Whatdoyoumeanbyviewplane?Aviewplaneisnothingbutthefilmplaneincamerawhichispositionedandorientedforaparticularshotofthescene.
21.Whatisview-planenormalvector?Thisnormalvectoristhedirectionperpendiculartotheviewplaneandit
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iscalledas[DXNDYNDZN]
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22.Whatisviewdistance?Theviewplanenormalvectorisadirectedlinesegmentfromtheviewplanetotheviewreferencepoint.Thelengthofthisdirectedlinesegmentisreferredtoasviewdistance
23.Defineprojection?Theprocessofconvertingthedescriptionofobjectsfromworldcoordinatestoviewingcoordinatesisknownasprojection
24.Whatyoumeanbyparallelprojection?Parallelprojectionisoneinwhichzcoordinatesisdiscardedandparallellinesfromeachvertexontheobjectareextendeduntiltheyintersecttheviewplane.
25.WhatdoyoumeanbyPerspectiveprojection?Perspectiveprojectionisoneinwhichthelinesofprojectionarenotparallel.Instead,theyallconvergeatasinglepointcalledthecenterofprojection.
26.WhatisProjectionreferencepoint?InPerspectiveprojection,thelinesofprojectionarenotparallel.Instead,theyallconvergeatasinglepointcalledProjectionreferencepoint.
27.WhatistheuseofProjectionreferencepoint?InPerspectiveprojection,theobjectpositionsaretransformedtotheviewplanealongtheseconvergedprojectionlineandtheprojectedviewofanobjectisdeterminedbycalculatingtheintersectionoftheconvergedprojectionlineswiththeviewplane.
28.Whatarethedifferenttypesofparallelprojections?Theparallelprojectionsarebasicallycategorizedintotwotypes,dependingontherelationbetweenthedirectionofprojectionandthenormaltothe
viewplane.Theyareorthographicparallelprojectionandobliqueprojection.
29.Whatisorthographicparallelprojection?Whenthedirectionoftheprojectionisnormal(perpendicular)totheviewplanethentheprojectionisknownasorthographicparallelprojection
30.Whatisorthographicobliqueprojection?Whenthedirectionoftheprojectionisnotnormal(notperpendicular)totheviewplanethentheprojectionisknownasobliqueprojection.
31.Whatisanaxonometricorthographicprojection?Theorthographicprojectioncandisplaymorethanonefaceofanobject.Suchanorthographicprojectioniscalledaxonometricorthographicprojection.
32.Whatiscavalierprojection?Thecavalierprojectionisonetypeofobliqueprojection,inwhichthedirectionofprojectionmakesa45-degreeanglewiththeviewplane.
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33.Whatiscabinetprojection?Thecabinetprojectionisonetypeofobliqueprojection,inwhichthedirectionofprojectionmakesanangleofarctan(2)=63.4-withtheviewplane.
34.Whatisvanishingpoint?Theperspectiveprojectionsofanysetofparallellinesthatarenotparalleltotheprojectionplaneconvergetoappointknownasvanishingpoint.
35.Whatdoyoumeanbyprinciplevanishingpoint.Thevanishingpointofanysetoflinesthatareparalleltooneofthethreeprincipleaxesofanobjectisreferredtoasaprinciplevanishingpointoraxisvanishingpoint.
36.Whatisviewreferencepoint?Theviewreferencepointisthecenteroftheviewingcoordinatesystem.Itisoftenchosentobeclosetooronthesurfaceofthesomeobjectinthescene.
UNITV
1.Definecomputergraphicsanimation?
Computergraphicsanimationistheuseofcomputergraphicsequipmentwherethegraphicsoutputpresentationdynamicallychangesinrealtime.Thisisoftenalsocalledrealtimeanimation.
2.Whatistweening?Itistheprocess,whichisapplicabletoanimationobjectsdefinedbyasequenceofpoints,andthatchangeshapefromframetoframe.
3.Defineframe?Oneoftheshapephotographsthatafilmorvideoismadeofisknownasframe.
4.Whatiskeyframe?Oneoftheshapephotographsthatafilmorvideoismadeoftheshapeofanobjectisknowninitiallyandforasmallnoofotherframescalledkeyframe
5.Whatispseudoanimation?Pseudoanimationiscreatingasequenceofstills,photographingorvideographingeachstillasoneframe,andthenlaterplayingbacktheframesatafasterspeed.
6.Whatisthenormalspeedofavisualanimation?Visualanimationrequiresaplaybackofatleast25framespersecond.
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7.Whatarethedifferenttricksusedincomputergraphicsanimation?a.ColorlookUpTablemanipulationb.Bitplanemanipulationc.UseofUDCSd.Specialdrawingmodese.Spritesf.Bitblitting
8.Whatiscolorlookuptable?Incolordisplayunititisnecessarytoread44-bitforeachpixelfrombuffer.Thisverytimeconsumingprocess.ToavoidthisvideocontrolleruseslookuptabletostoremanyentriesofpixelvalesinRGBformat.Thislookuptableiscommonlyknownascolorlookuptable.
9.Whatissolidmodeling?Theconstructionof3dimensionalobjectsforgraphicsdisplayisoftenreferredtoassolidmodeling.
10.Whatisanintuitiveinterface?Theintuitiveinterfaceisone,whichsimulatesthewayapersonwouldperformacorrespondingoperationonrealobjectratherthanhavemenucommand.
11.WhatisSprite?ASpriteisgraphicsshapeinanimationandgamesprograms.EachspriteprovidedinthesystemhasitsownmemoryareasimilartobutsmallerthanpixelRAM.
12.WhatistheUDCtechnique?UDCstandsforUserDefinedCharacterset.Itisgraphicsanimationtrick,whichisusedinearlymicrocomputersystem.
13.Whatistheuseofhiddenlineremovingalgorithm?Thehiddenlineremovalalgorithmdeterminesthelines,edges,surfacesorvolumesthatarevisibleorinvisibletoanobserverlocatedataspecificpoint
inspace.
14.Whatiscomputergraphicsrealism?Thecreationofrealisticpictureincomputergraphicsisknownasrealism.Itisimportantinfieldssuchassimulation,design,entertainments,advertising,research,education,command,andcontrol.
15.Howrealisticpicturesarecreatedincomputergraphics?Tocreatearealisticpicture,itmustbeprocessthesceneorpicturethroughviewing-coordinatetransformationsandprojectionthattransformthree-dimensionalviewingcoordinatesontotwo-dimensionaldevicecoordinates.
16.WhatisFractals?AFractalisanobjectwhoseshapeisirregularatallscales.
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17.WhatisaFractalDimension?Fractalhasinfinitedetailandfractaldimension.Afractalimbeddedinn-dimensionalspacecouldhaveanyfractionaldimensionbetween0andn.TheFractalDimensionD=LogN/LogSWhereNistheNoofPiecesandSistheScalingFactor.
18.Whatisrandomfractal?Thepatternsintherandomfractalsarenolongerperfectandtherandomdefectsatallscale.
19.Whatisgeometricfractal?Ageometricfractalisafractalthatrepeatsself-similarpatternsoverallscales.
20.WhatisKochcurve?TheKochcurvecanbedrawnbydividinglineinto4equalsegmentswithscalingfactor1/3.andmiddle2segmentsaresoadjustedthattheyformadjustmentsidesofanequilateraltriangle.
21.Whatisturtlegraphicsprogram?TheturtleprogramisaRobertthatcanmovein2dimensionsandithasa
pencilfordrawing.Theturtleisdefinedbythefollowingparameters.
g.Positionoftheturtle(x,y)h.Headingoftheturtle0theanglefromthexaxis.22.Whatisgraftals?Graftalsareapplicabletorepresentrealisticrenderingplantsandtrees.AtreeisrepresentedbyaStringofsymbols0,1,[,]
23.WhatisaParticlesystem?Aparticlesystemisamethodformodelingnaturalobjects,orotherirregularlyshapedobjects,thatexhibitfluid-likeproperties.Particlesystemsa
resuitableforrealisticrenderingoffuzzyobjects,smoke,seaandgrass.
24.Givesomeexamplesforcomputergraphicsstandards?i.CORETheCoregraphicsstandardj.GKS--TheGraphicsKernelsystemk.PHIGSTheProgrammersHierarchicalInteractiveGraphicsSystem.l.GSXTheGraphicssystemextensionm.
NAPLPSTheNorthAmericanpresentationlevelprotocolsyntax.DetailedAnswers
UNITI
1.Explainrefreshcathoderaytube?.
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Abeamofelectrons,emittedbyanelectrongun,passesthroughfocusinganddeflectionsystemsthatdirectthebeamtowardspecifiedpositionsonthephosphorcoatedarea.
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Theyproduceawiderrangeofcolors.Hasthreephosphorcolordotsateachpixelposition
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.Oneemitsredlight,anotheremitsgreenlight,andthethirdemitsabluelight.Thethreebeamsaredeflectedandfocusedasagroupontotheshadowmask,whichcontainsaseriesofholesalignedwithaphosphordotpatterns..Whenthethreebeamspassesthroughaholeintheshadowmask,theyactivateadottriangle,whichappearsasasmallcolorspotonthescreen.3.Explaindirectviewstoragetubesandliquidcrystaldisplays?LiquidcrystaldisplaysReferstothecompoundshavingcrystallinearrangementofmoleculesflowofliquidTwoplateseachglassplatecontainsalightpolarizedthatarerightanglestoeachotherTwotypesPassivematrixLCD
ActivematrixLCDDirectviewstoragetubes
AlternativemethodformaintainingascreenimageStorespictureinformationasachargedistributionVerycomplexpicturescanbedisplayedatveryhighresolutionsToeliminatethepicturesectiontheentirescreenmustbeerasedTheerasingandredrawingprocesscantakeseveralsecondsfora
picture4.ExplainRasterscansystems?
.Severalprocessingunits.Containsaspecialpurposeprocessor,calledvideocontrollerordisplaycontroller.VideocontrollerAfixedareaofthesystemmemoryisreservedfortheframebuffer,andthevideocontrollerisgivenaccesstotheframe-
buffermemoryTowregistersareusedtostorethecoordinatesofthescreenpixelsThevalueisstoredintheframebufferforthispixelpositionisthenretrievedandusedtosettheintensityoftheCRTbeamInitiallythexregisterissetto0andtheyregisterissettoymax
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Thenthexregisterisincrementedby1,andtheprocessrepeatedforthenextpixelonthetopscanlineThisprocessisrepeatedforeachpixelalongthescanline
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Afterthelastpixelsonthetopscanlinehasbeenprocessed,thexregisterisresetto0andtheyregisterisdecrementedby1.Theprocedureisrepeatedfroeachsuccessiveline.FramebufferlocationsandthecorrespondingscreenpositionsarereferencedasCartesiancoordinatesSystemBusCPUSystemFrameMemoryBufferVideocontrollerI/Odevice
4.Explainthefollowing?1.Z-mouse2.Joysticks
3.Touchpanels4.Imagescanners5.DatagloveZ-Mouse:.Includethreebuttons.Athumbwheelontheside,atrackballonthetop,andastandardmouseballunderneath..Thisdesignprovidessixdegreesoffreedomtoselectanobjectfrom
thespatialposition..Witthiswecanpickupanobject,rotateitandwecanmoveitinanydirection.UsedinvirtualrealityandCADsystemsJoysticks
ConsistsofsmallverticallivermountedonabaseUsedtomovethecursoraroundthescreen
ThescreencursorismovedaccordingtothedistanceOneortwobuttonsisusuallyintendedforsignalingcertainactionsTouchpanels
ThreetypesOpticaltouchpanel
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ElectricaltouchpanelAcousticaltouchpanelAllowselectingthescreenpositionwiththetouchoffinger.Touchinputcanberecordedusingoptical,electricalmethodsImagescanners
.Drawings,colorandblackandwhitephotosortextcanbegivenasaninputtothecomputerwithanopticalscanningmechanism..AccordingtoreflectedlightintensitythegradationsofgrayscaleorcolorcanbestoredinanarrayDataglove
.Constructedwithaseriesofsensorsthatcandetecthandandfingermotions.Thetransmittingandreceivingantennascanbestructuredasasetofthreemutuallyperpendicularcols,formingathreedimensional
Cartesiancoordinatessystem..Electromagneticcouplingbetweenthethreepairsofcoilisusedtoprovideinformationaboutthepositionandorientationofhand.UNITII
1.ExplainindetailabouttheDDAscanconversionalgorithm?Thedigitaldifferentialanalyzerisascanconversionalgorithmbasedoncalculationeitheryorxusingthefollowingeuations
y=mx
x=y/m
Samplethelineatunitintervalsinonecoordinateanddeterminecorrespondingintegervaluesnearestthelinepathforthecoordinates
SampleatXintervals(x=1)andcomputeeachsuccessiveYvalueasYk+1=Yk+m
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Forlineswithpositiveslopegreaterthan1,reversetherolesofXandY.SampleatunitYintervals(y=1)andcalculateeachsuccessiveXvalueasXk+1=Xk+1/m
Algorithm
Step1:Inputthelineendpointsandstoretheleftendpointin(x1,y1)andright
endpointin(x2,y2)Step2:Calculatethevaluesofxandyusingx=xbxa,y=ybyaStep3:ifthevaluesofx>yassignvaluesofstepsasxotherwisethevalues
ofstepsasyStep4:CalculatethevaluesofXincrementandYincrementandassignthevaluex=xaandy=ya
Step5:fork=1tostepsdoX=X+XincrementY=Y+YincrementPutpixel(ceil(x),ceil(y),15)
Step6:End
2.ExplainBresenhamslinedrawingalgorithm?InBresenhamsapproachthepixelpositionalongalinepatharedeterminedbysamplingunitXintervals.Startingfromtheleftendpoint(X0,Y0)ofagivenlinewesteptoeachsuccessivecolumnsandplotthepixelwhosescanlineY-valueisclosesttothelinepath.AssumingtheKthstepinprocess,determinedthatthepixelat(Xk,Yk)decidewhichpixeltoplotincolumnXk+1.Thechoicesare(Xk+1,Yk)and(Xk+1,
Yk+1)
Algorithm
Step1:Inputthelineendpointsandstoretheleftendpointin(X0,Y0)Step2:Load(X0,Y0)intotheframebufferStep3:Calculateconstantsx,y,2y,-2x,andobtainthedecisionparametersas
P0=2yxStep4:AteachXkalongtheline,startingatk=0,performthefollowingtestIfPk
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thecircumferenceofacirclecenteredontheoriginas(X0,Y0)=(0,r)Step2:CalculatetheinitialvaluesofthedecisionparameterasP0=5/4rStep3:Ateachpositionstartingatkperformthefollowingtest:IfPk=YPk+1=Pk+2YOtherwise,thenextpointis(Xk+1,Yk+1)andPk+1=Pk+2Y-2XStep5:Repeatsteps4Xtimes
4.ExplainEllipsegeneratingAlgorithm?AlgorithmStep1:Inputradiusrx,ryandellipsecenter(Xc,Yc)andobtainthefirstpointonthecircumferenceofacirclecenteredontheoriginas(X0,Y0)=(0,ry)Step2:Calculatetheinitialvaluesofthedecisionparameterinregion1as
P10=ry2-rx2ry+1/4rx2
Step3:AteachpositionstartingatXkpositioninregion1,startingatk=0,performthefollowingtest:IfPk0,thenextpointtoplotis(Xk,Yk-1)and
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22
P2k+1=P2k-2ryYk+1+rxOtherwisethenextpointis(Xk+1,Yk-1)and
222
P2k+1=P2k-2ryYk+1-2rxYk+1+rxStep6:DeterminesymmetrypointsintheotherthreeoctantsStep7:Moveeachpixelposition(X,Y)ontothecircularpathcentredon
(Xc,Yc)andplotthecoordinatevaluesasX=X+XcY=Y+Yc
22
Step8:Repeatstepsforregion1until2ryX>=2ryY
5.ExplainBoundaryfillAlgorithm?
.Iftheboundaryisspecifiedinasinglecolor,thefillalgorithm
proceedsoutwardpixel-by-pixeluntiltheboundarycolorisencountered.Thisiscalledboundaryfillalgorithm.Theboundaryfillprocedureacceptsasinputthecoordinatesofaninteriorpoint(x,y),afillcolor,andaboundarycolor..Startingfrom(x,y),theprocedureteststheneighboringpositionstodeterminewhethertheyareboundarycolor..Ifnot,theyarepaintedwiththefillcolor,andtheneighborsaretested..Thisprocesscontinuesuntilallpixelsuptotheboundarycolorfortheareahavebeentested
.Twomethods
.4-connected4neighbouringpointsareconected.8-connectedcorrectlyfilltheinterioroftheareadefinedprogram
voidboundaryfill(intx,inty,intfill,intboundary)
{intcurrent;
current=getpixel(x,y);if((current!=boundary)&&(current!=nil){setColor(fill);setPixel(x,y);boundaryfill(x+1,y,fill,boundary);boundaryfill(x-1,y,fill,boundary);
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boundaryfill(x,y+1,fill,boundary);boundaryfill(x,y-1,fill,boundary);}
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}
UNITIII
1.Explainreflectionandshear?ReflectionItisamirrorimageofanobjectRotatingabout180degreeFlatobjectmovinginthexyplaneReflectionaboutyaxisflipsxcoordinatesReflectionpointaspivotpointissameasaboveToobtainthetransformationmatrixforreflectiondiagonalisy=-xSequence
Clockwiserotationby45degreeReflectionaboutyaxisCounterwiserotationby45degreeShear
Internallayercausetoslideovereachothercalledshear
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TransformscoordinatepositionasX=x+shx.y,Y=yShiftinthepositionofobjectsrelativetoshearingreferencelinesareequivalenttotranslations2.ExplainLiangBarskylineclippingFasterlineclipperoftheparametricequationofalinesegmentLineparalleltooneoftheclippingboundariesLineintersectstheextensionofboundarykIfu1>u2lineisoutsidetheclippingwindowElseinsidetheclippingwindowClippingisdoneusingthereflectionintheclipwindow3.ExplainSutherlandHodgemanpolygonclippingClippingpolygonwhichliesinsidetheclippingwindow
FourpossiblecasesIfthefirstvertexisoutsidethewindowboundaryandthesecondvertexinsideIfthefirstvertexisinsidethewindowboundaryandthesecondvertexoutsideIfbothareoutsideIfbothareinside
RepeattheprocessofalgorithmConvexpolygonarecorrectlyclippedusingthisclippingConcaveandconvexpolygonarealsoused4.ExplainaboutclippingoperationsClipapicturefromeitheroutsideorinsidearegionknownasclippingAlsocalledasclippingalgorithmTheregionagainsttheobjectisknownasclipwindow
Clippingoperationsondifferenttypesofobjects
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PointclippingPolygonclippingAreaclippingLineclippingCurveclippingTextclippingPolygonandlineclippingarethestandardclippingcomponentsUNITIV
1.Explainthethreedimensionaldisplaymethods?ParallelprojectionTheproductionofthe2Ddisplayofthe3Dsceneiscalledprojection
ProjectpointsontheobjectsurfacealongtheparallellinesontothedisplayplaneDifferent2DviewsofobjectscanbeproducedbyprojectingthevisiblepointsPerspectiveprojectionDonebytheprojectingpointstothedisplayplanealongtheconvergingpointsCausestheobjectsfartherfromtheviewingpoint
shouldbesmallerofthesamesizedobjectpresenthere.DepthCUEINGBasicproblemforvisualizationtechniquesiscalleddepthcueingSome3DobjectsarewithoutdepthinformationVisiblelineandsurfaceidentificationTohighlightthevisiblelines
Displayvisiblelinesasdashedlines
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RemovingtheinvisiblelinesSurfacerenderingLighteningconditionsinthescreenAssignedcharacteristicsDegreeoftransparencyHowroughorsmooththesurfacesaretobeExplodedandcutawayviewsThreedimensionalandstereoscopicviews2.ExplainsplinerepresentationItisreferredtoacurvedrawninadifferentmannerInterpolationandapproximationsplinesSetofcoordinatepointscalledcontrolpoints
Curvecanbetranslated,rotatedandscaledEnclosingasetofpointscalledconvexhullSetofconnectedpointsisoftencalledcontrolgraphParametriccontinuityconditionGeometriccontinuityconditionSplinespecification3.ExplainBeziercurvesandsurfaces
HavenumberofpropertiesCanbefittedtoanynumberofcontrolpointsPolynomialfunctionsbetweenp0andpnnP(u)=pkBEZk,n(u)K=0
Calculatedx(u),y(u),z(u)
PropertiesofBeziercurvesCubicBeziercurvesDesigntechniquesinBeziercurvesBeziersurfaces
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4.ExplaingeneralthreedimensionalrotationsTransformationsequencesP=T.Rx().T.PRotationinfivestepsTranslatetheobjectthatrotatesinparallelcoordinateaxisRotatetheobjectwithonecoordinateaxisApplyinverserotationtoitsoriginalpositionApplyinversetranslationtoitsoriginalpositionV=p2p1AfterrotationtooriginalpositionR()=T.M.T
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UNITV
1.ExplainBackfacedetectionmethodandDepthbuffermethodBackfaceDetectionmethodFastandsimpleobjectspacemethodForidentifyingthebackfacesofapolyhedronBasedioninsideoutsidetestPlaneparametersA,B,C,DAx+By+Cz+D
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2.ExplainareasubdivisionandA-BuffermethodABufferMethodExtensionideaofthedepthbuffermethodItrepresentsanantialiased,areaaveraged,accumulation-buffermethodOnlyonevisiblesurfaceTwofieldsDepthfieldStoresapositiveornegativerealnumberIntensityfieldStoresasurfaceintensityinformationorapointervalueDataforeachsurfaceinthelinkedlistincludesRGBintensitycomponents
OpacityparametersDepthPercentofareacoverageSurfaceidentifierPointertonextsurfaceAreaSubDivisionMethod
Imagespacemethod
TherelativecharacteristicofsurfaceareSurroundingsurfaceInsidesurfaceOutsidesurfaceConditionsforsubdivisionAllsurfacesareoutsidesurfaceswithrespecttothearea
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OnlyoneinsideAsurroundingsurfacewithintheareaboundaries3.ExplainDepthsortingmethodBothimageandobjectspaceoperations]PerformthebasicfunctionSurfacearesortedinorderofdecreasingdepthSurfacearescanconvertedinorder,startingwiththesurfaceofgreatestdepthOftenreferredaspaintersalgorithmTestlistedintheorderofincreasingdifficultySurfacedonotoverlapProjectionsofthetwosurfacesontotheviewplanedonotoverlap4.Explainkeyframesystems
KeyframesystemsMotionpathcanbegivenwithakinematicsdescriptionPhysicallybasedonforceactingobjectFrameintoindividualcomponentorobjectcalledcellsMorphing
Transformationofobjectshapesfromoneformtoanotheriscalledmorphing
TwokeyframesforanobjecttransformationPreprocessingusingvertexcountSimulatingaccelerations
Timeintervalbetweenkeyframeisdividedinton+1t=(t2t1)/n=1tBj=t1+jt,j=1,2,3,Timeforjthin-betweenistBj=t1+t[(1-cos[j/(n+1)])/2],j=1,2,3,.
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