【文档说明】计算机图形学computer-graphics课件7.ppt，共(45)页，1.108 MB，由小橙橙上传

转载请保留链接：https://www.ichengzhen.cn/view-77496.html

以下为本文档部分文字说明：

InputandInteractionYuanfengZhouShandongUniversitySoftwareCollege1Objectives•Introducethebasicinputdevices-Phys

icalDevices-LogicalDevices-InputModes•Event-driveninput•Introducedoublebufferingforsmoothanimations•ProgrammingeventinputwithGLUT2ProjectSke

tchpad•IvanSutherland(MIT1963)establishedthebasicinteractiveparadigmthatcharacterizesinteractivecomputerg

raphics:-Userseesanobjectonthedisplay-Userpointsto(picks)theobjectwithaninputdevice(lightpen,mouse,trackball)-Ob

jectchanges(moves,rotates,morphs)-Repeat3InteractionwithGraphicsSystem4ChangeImageReacttoChangeGraphicsSystemUserInputDeviceDisplayGraph

icalInput•Devicescanbedescribedeitherby-Physicalproperties•Mouse•Keyboard•Trackball(Thinkpad)-Logicalproperti

es•WhatisreturnedtoprogramviaAPI(ApplicationProgrammingInterface)–Aposition–Anobjectidentifier•Modes-

Howandwheninputisobtained•Requestorevent5LogicalProperties6ApplicationModelApplicationProgramGraphicsSystemOutputDevicesInputDevicesAPIFunctionC

allsorProtocolDataWM_LBUTTONDOWN#defineON_BN_LBUTTONDOWN(id,memberFxn)voidCMyProgram::OnLButtonDown(UINTnF

lags,CPointpoint){processingcode…CButton::OnLButtonDown(nFlags,point);}PhysicalDevices7mousetrackballlightpendatatabletjoystickspaceba

llLogicalDevices•ConsidertheCandC++code-C++:cin>>x;-C:scanf(“%d”,&x);•Whatistheinputdevice?-Can’ttellfromthecode-Couldbekeyb

oard,file,outputfromanotherprogram•Thecodeprovideslogicalinput-Anumber(anint)isreturnedtotheprogramregardlessofthep

hysicaldevice8GraphicalLogicalDevices•Graphicalinputismorevariedthaninputtostandardprogramswhichisusuallynumbers,char

acters,orbits•TwoolderAPIs(GKS77’,PHIGS90’)definedsixtypesoflogicalinput:-Locator:returnaposition-Pick:returnIDofanobject-Keyboard:retu

rnstringsofcharacters-Stroke:returnarrayofpositions-Valuator:returnfloatingpointnumber-Choice:returnoneofnitems910XWindowInput•TheXWindowS

ystemintroducedaclient-servermodelforanetworkofworkstations-Client:OpenGLprogram-GraphicsServer:bitmapdisplaywithapointingdevicea

ndakeyboardDisplayListinOpenGL•Matrixcomputation•Imagedisplay•Light,material•Texture•Polygonalobjects

display11DisplayListinOpenGL•voidglNewList(GLuintlist,GLenummode);•mode:GL_COMPILEandGL_COMPILE_AND_EXECUTE•voidglEndList(void);•NOTincludedinDisplay

List:•glDeleteLists()glIsEnable()•glFeedbackBuffer()glIsList()•glFinish()glPixelStore()•glGenLists()glRenderMode()•glGet*()gl

SelectBuffer()12DisplayListinOpenGL•Example:GLuintlistName=1;voidmyinit(void){glNewList(listName,GL_COMPILE);glColor3f(1.0,0.0,0

.0);glBegin(GL_TRIANGLES);glVertex2f(0.0,0.0);glVertex2f(1.0,0.0);glVertex2f(0.0,1.0);glEnd();glTranslatef(

1.5,0.0,0.0);glEndList();glShadeModel(GL_FLAT);}13voidCALLBACKdisplay(void){GLuinti;glClear(GL_COLOR_BUFFER_B

IT);glColor3f(0.0,1.0,0.0);glPushMatrix();for(i=0;i<5;i++)glCallList(listName);drawLine();glPopMatrix();glFl

ush();}InputMode•Inputdevicescontainatriggerwhichcanbeusedtosendasignaltotheoperatingsystem-Buttononm

ouse-Pressingorreleasingakey•Whentriggered,inputdevicesreturninformation(theirmeasure)tothesystem-Mouser

eturnspositioninformation-KeyboardreturnsASCIIcode14RequestMode•Inputprovidedtoprogramonlywhenusertriggersthedevice•

Typicalofkeyboardinput-Canerase(backspace),edit,correctuntilenter(return)key(thetrigger)isdepressed151.Programrequestsmeasureofadeviceandblocks.2.

Measureprocessmaintainscurrentmeasure.3.Triggerprocesssignalsmeasureprocesstoreturnmeasure.request_locator(device_id,&measure);EventMode•Mostsys

temshavemorethanoneinputdevice,eachofwhichcanbetriggeredatanarbitrarytimebyauser•Eachtriggergeneratesaneventwh

osemeasureisputinaneventqueuewhichcanbeexaminedbytheuserprogram16glutMainLoop();EventTypes•Window:resize,expose,iconif

y•Mouse:clickoneormorebuttons•Motion:movemouse•Keyboard:pressorreleaseakey•Idle:nonevent-Definewhatshouldbedoneifnoothereve

ntisinqueue17Callbacks•Programminginterfaceforevent-driveninput•Defineacallbackfunctionforeachtypeofeventthegraphicssystemrecognizes

•Thisuser-suppliedfunctionisexecutedwhentheeventoccurs•GLUTexample:glutMouseFunc(mymouse)18mousecall

backfunction19GLUTcallbacksGLUTrecognizesasubsetoftheeventsrecognizedbyanyparticularwindowsystem(Windows,X,Macintosh)-glutDisplayFunc-glutMous

eFunc-glutReshapeFunc-glutKeyboardFunc-glutIdleFunc-glutMotionFunc-glutPassiveMotionFuncGLUTEventLoop•Recallthatthelastlineinmain

.cforaprogramusingGLUTmustbeglutMainLoop();whichputstheprograminaninfiniteeventloop•Ineachpassthroughtheeve

ntloop,GLUT-looksattheeventsinthequeue-foreacheventinthequeue,GLUTexecutestheappropriatecallbackfunctionifoneisdefined-ifnocallbackisdefinedfo

rtheevent,theeventisignored20Usingglobals•TheformofallGLUTcallbacksisfixed-voidmydisplay()-voidmymouse(GLintbutton,GLintstate,GLintx,GLin

ty)•Mustuseglobalstopassinformationtocallbacks21floatt;/*global*/voidmydisplay(){/*drawsomethingthatdependsont}GL

UTDisplayEventTrigger:GLUTdeterminesthatthewindowneedstoberedisplayed.Adisplayeventisgeneratedwhenthewindo

wisfirstdrawn.Callbackfunctionform:voiddisplay();Registration:glutDisplayFunc(display);ThedisplaycallbackisexecutedwheneverGLUTdeterminesthatthew

indowshouldberefreshed,forexampleWhenthewindowisfirstopenedWhenthewindowisreshapedWhenawindowisexposedWhentheuserprogramdecid

esitwantstochangethedisplay23Postingredisplays•Manyeventsmayinvokethedisplaycallbackfunction-Canlead

tomultipleexecutionsofthedisplaycallbackonasinglepassthroughtheeventloop•WecanavoidthisproblembyinsteadusingglutPostRedisplay();whichsetsaf

lag.•GLUTcheckstoseeiftheflagissetattheendoftheeventloop•Ifsetthenthedisplaycallbackfunctionisexecuted24AnimatingaDisplay•Whenwe

redrawthedisplaythroughthedisplaycallback,weusuallystartbyclearingthewindow-glClear()thendrawthealtereddisplay•Problem:thedrawingofinformationinthef

ramebufferisdecoupledfromthedisplayofitscontents-Graphicssystemsusedualportedmemory•Hencewecanseepartiallydrawndisplay-Seetheprograms

ingle_double.cforanexamplewitharotatingcubeGLUTMouseEventTrigger:Anymousebuttonisdepressedorreleased.Callbackfunction

form:voidmouse_callback_func(intbutton,intstate,intx,inty);Registration:glutMouseFunc(mouse_callback_function);GLUTDefi

nedMouseConstantsGLUT_LEFT_BUTTONGLUT_MIDDLE_BUTTONGLUT_RIGHT_BUTTONGLUT_UPGLUT_DOWNSystemswithonlyonemousebuttoncano

nlygenerateaGLUT_LEFT_BUTTONcallback.GLUTReshapeEventTrigger:ActivewindowisresizedCallbackfunctionform:voidreshape_func(GLsizeiw,GLsizeih);Reg

istration:glutReshapeFunc(reshape_func);GLUTMoveEventTrigger:Themouseismovedwhileoneormoremousebuttons

arepressed.Callbackfunctionform:voidmotion_func(intx,inty);Registration:glutMotionFunc(motion_func);GLUTKeyboardEve

ntTrigger:Anykeyisdepressed.Callbackfunctionform:voidkeyboard_function(unsignedcharkey,intx,inty);Registration:glutKeyboardFunc(keyboard_function);

OtherDefinedEventsinGLUTglutPassiveMotionFuncglutVisibilityFuncglutEntryFuncglutSpecialFuncglutSpaceballMotionFuncglutSpaceballRotateFuncglutS

paceballButtonFuncglutButtonBoxFuncglutDialsFuncglutTabletMotionFuncglutTabletButtonFuncglutMenuStatusFuncExample:Simpl

eSquareDrawingProgram•Openawindow.•Clearittoblack.•Drawaboxatlocationofthemouseeachtimetheleftbuttonisclicked.

ColorofboxshouldberandomlyselectedfromRGBspace.•Clearwindowwhenresized.•Quitwhenrightbuttonisclicked.SquarePro

gramSourceCodeSlide1/*ThisprogramillustratestheuseoftheglutlibraryforinterfacingwithaWindowSystem*//*Theprogramopensawindow,clearsittoblack,the

ndrawsaboxatthelocationofthemouseeachtimetheleftbuttonisclicked.TherightbuttonexitstheprogramTheprogramalsoreactscorrectlywhen

thewindowismovedorresizedbyclearingthenewwindowtoblack*/#include<GL/gl.h>#include<GL/glut.h>/*globals*/GLsizeiwh=500,ww=500;/*initialwindowsize

*/GLfloatsize=3.0;/*halfsidelengthofsquare*/SquareProgramSourceCodeSlide2voiddrawSquare(intx,inty){y=wh-y;glColor3f((char)random()%256,

(char)random()%256,(char)random()%256);glBegin(GL_POLYGON);glVertex2f(x+size,y+size);glVertex2f(x-size,y+size);glVertex2f(x-s

ize,y-size);glVertex2f(x+size,y-size);glEnd();glFlush();}SquareProgramSourceCodeSlide3voidmyReshape(GLsizeiw,GLsizeih){/*adjust

clippingbox*/glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(0.0,(GLdouble)w,0.0,(GLdouble)h,-1.0,1.0);

glMatrixMode(GL_MODELVIEW);glLoadIdentity();/*adjustviewportandclear*/glViewport(0,0,w,h);glClearColor(0.0,0.0

,0.0,0.0);glClear(GL_COLOR_BUFFER_BIT);glFlush();/*setglobalsizeforusebydrawingroutine*/ww=w;wh=h;}SquareProgramSourceCodeSlide4voidmyinit(void){gl

Viewport(0,0,ww,wh);/*Pick2DclippingwindowtomatchsizeofscreenwindowThischoiceavoidshavingtoscaleobjectcoordi

nateseachtimewindowisresized*/glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(0.0,(GLdouble)ww,0.0,(GLdouble)wh,-1.0,

1.0);/*setclearcolortoblackandclearwindow*/glClearColor(0.0,0.0,0.0,0.0);glClear(GL_COLOR_BUFFER_BIT);glF

lush();/*callbackroutineforreshapeevent*/glutReshapeFunc(myReshape);}SquareProgramSourceCodeSlide5voidmouse(intbtn,intstate,intx,inty){if(btn==GLUT_R

IGHT_BUTTON&state==GLUT_DOWN)exit();}intmain(intargc,char**argv){glutInit(&argc,argv);glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);glut

CreateWindow("square");myinit();glutReshapeFunc(myReshape);glutMouseFunc(mouse);glutMotionFunc(drawSquare);glutMainLoop();}Outputof“Square”p

rogramImplementingChoice:MenusinGLUT•Foursteps:-Createmenu:glutCreateMenu(menu);-Definemenuentries:glutAddMenuEntry-Attachmenutoamou

sebutton:gluAttachMenu-Definecallbackfunction:voidmenu(intid);CreatingaMenuinGLUTintglutCreateMenu(void(*func)(intvalue));Create

sanewpop-upmenu.Returnsauniqueintegeridentifierforthemenu.Takesasargumentapointertoasinglecallbackfunctionthattakesanintegerargumen

t.Theintegerargumentofthecallbackismappedtothemenuchoice.Setsthecurrentmenutothenewlycreatedmenu.MenuIdentifierCall

backFunctionChoiceAssociatingaMenuwithaMouseKeyvoidglutAttachMenu(intbutton);Associatestheselectedbuttonwiththecurrentmenu.buttonisselectedfr

omtheGLUTdefinedbuttonconstants:GLUT_LEFT_BUTTON,GLUT_MIDDLE_BUTTON,GLUT_RIGHT_BUTTONAddingEntriestotheMenuvoidglutAddMenuE

ntry(char*name,intvalue);Stringtoappearinmenuentry.Valuetobepassedtocallbackfunction.Addsamenuentrytothebottomofthecurrentmenu.Buildinga

Sub-menuvoidglutAddSubMenu(char*name,intmenu);Stringtodisplayinthemenuitemfromwhichtocascadesub-menu.Identifierofmenutocascadefro

mthissub-menuitem.DoubleBuffering•Insteadofonecolorbuffer,weusetwo-FrontBuffer:onethatisdisplayedbutnotwrittento-BackBuffer:onethatiswrittentobutnotd

isplayed•Programthenrequestsadoublebufferinmain.c-glutInitDisplayMode(GL_RGB|GL_DOUBLE)-Attheendofthedisplay

callbackbuffersareswapped43voidmydisplay(){glClear(GL_COLOR_BUFFER_BIT|….)./*drawgraphicshere*/.glutSwapBuffers()}44Usingt

heidlecallback•Theidlecallbackisexecutedwhenevertherearenoeventsintheeventqueue-glutIdleFunc(myidle)-Usefulforanimationsv

oidmyidle(){/*changesomething*/t+=dtglutPostRedisplay();}Voidmydisplay(){glClear();/*drawsomethingthatdependsont*/glutSwapBuffers();}45Usingglo

bals•TheformofallGLUTcallbacksisfixed-voidmydisplay()-voidmymouse(GLintbutton,GLintstate,GLintx,GLinty)•Mustuseglobalstopassinforma

tiontocallbacksfloatt;/*global*/voidmydisplay(){/*drawsomethingthatdependsont}