《opengl计算机三维图形程序设计》三维程序设计-opengl

虚拟现实、军事仿真三维游戏网上三维交互

电子商务、虚拟商城、虚拟社区编辑ppt三维图形实时渲染引擎开源系统

OGRE(/)OSG()

IrrIichtengine(/)

delta3d商业游戏引擎

WorldofWarcraft(没发布）AIONCryEngine2，Crytek出品

由EpciGames研发的Unreal引擎

编辑pptOpenGL现状TheKhronosGroup-MediaAuthoringandAccelerationTheKhronosGroupisanindustryconsortiumcreatingopenstandardsfortheauthoringandaccelerationofparallelcomputing,graphicsanddynamicmediaonawidevarietyofplatformsanddevices.AllKhronosmembersareabletocontributetothedevelopmentofKhronosAPIspecifications,areempoweredtovoteatvariousstagesbeforepublicdeployment,andareabletoacceleratethedeliveryoftheircutting-edge3Dplatformsandapplicationsthroughearlyaccesstospecificationdraftsandconformancetests./编辑pptOpenGL现状TheOpenGL4.2andOpenGLShadingLanguage4.20SpecificationswerereleasedonAugust8,2011DirectX11编辑pptOpenCLOpenCL-Theopenstandardforparallelprogrammingofheterogeneoussystems.OpenCL™isthefirstopen,royalty-freestandardforcross-platform,parallelprogrammingofmodernprocessorsfoundinpersonalcomputers,serversandhandheld/embeddeddevices.OpenCL(OpenComputingLanguage)greatlyimprovesspeedandresponsivenessforawidespectrumofapplicationsinnumerousmarketcategoriesfromgamingandentertainmenttoscientificandmedicalsoftware.WebCL-HeterogeneousparallelcomputinginHTML5webbrowsers.TheWebCLworkinggroupisworkingtodefineaJavaScriptbindingtotheKhronosOpenCLstandardforheterogeneousparallelcomputing.WebCLwillenablewebapplicationstoharnessGPUandmulti-coreCPUparallelprocessingfromwithinaWebbrowser,enablingsignificantaccelerationofapplicationssuchasimageandvideoprocessingandadvancedphysicsforWebGLgames.WebCLisbeingdevelopedinclosecooperationwiththeWebcommunityandhasthepotentialtoextendthecapabilitiesofHTML5browserstoacceleratecomputationallyintensiveandrichvisualcomputingapplications.编辑ppt第一章OpenGL概览图形硬件的软件接口跨平台—Windows,linuxGLU(OpenGLUtilityLibrary)建模（曲线、曲面（NURBS)）是一个状态机。它将一直处于您指定的各种状态（或模式）中，直到您修改这些状态为止。编辑pptOpenGL程序框架打开一个窗口创建一个OpenGLContextWhile(!Stop){if(有事件）

{更新数据

绘制当前帧}else空闲处理

}编辑ppt一个简单的OpenGL程序#include<whateverYouNeed.h>main(){InitializeAWindowPlease();glClearColor(0.0,0.0,0.0,0.0);glClear(GL_COLOR_BUFFER_BIT);glColor3f(1.0,1.0,1.0);glOrtho(0.0,1.0,0.0,1.0,-1.0,1.0);glBegin(GL_POLYGON);glVertex3f(0.25,0.25,0.0);glVertex3f(0.75,0.25,0.0);glVertex3f(0.75,0.75,0.0);glVertex3f(0.25,0.75,0.0);glEnd();glFlush();UpdateTheWindowAndCheckForEvents();}编辑pptOpenGL的要点OpenGL函数的语法OpenGL是一个状态机OpenGL渲染流水线显示列表求值程序顶点操作图元装配PrimitiveAssembly像素操作纹理装配光栅化片元操作编辑ppt数据类型编辑ppt动画open_window();for(i=0;i<1000000;i++){clear_the_window();draw_frame(i);wait_until_a_24th_of_a_second_is_over();}双buffer状态下的绘制open_window_in_double_buffer_mode();for(i=0;i<1000000;i++){clear_the_window();draw_frame(i);swap_the_buffers();}编辑ppt帧频的变化theswap_the_buffers()routinewaitsuntilthecurrentscreenrefreshperiodisoversothatthepreviousbufferiscompletelydisplayed.编辑pptOpenGL程序练习编辑ppt第二章状态管理和绘制几何体ClearingtheWindow编辑pptSpecifyingaColor

glColor3f(1.0,0.0,0.0);redglColor3f(0.0,1.0,0.0);greenglColor3f(1.0,1.0,0.0);yellowglColor3f(0.0,0.0,1.0);blueglColor3f(1.0,0.0,1.0);magentaglColor3f(0.0,1.0,1.0);cyanglColor3f(1.0,1.0,1.0);white编辑pptForcingCompletionofDrawing

glFlush()glFinish()编辑pptCoordinateSystemSurvivalKitExample2-1:ReshapeCallbackFunctionvoidreshape(intw,inth){glViewport(0,0,(GLsizei)w,(GLsizei)h);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(0.0,(GLdouble)w,0.0,(GLdouble)h);}编辑pptPoints,Lines,PolygonsVertex(x,y,z,w)First,theedgesofOpenGLpolygonscan'tintersect(amathematicianwouldcallapolygonsatisfyingthisconditionasimplepolygon).OpenGLpolygonsmustbeconvex,meaningthattheycannothaveindentations.Statedprecisely,aregionisconvexif,givenanytwopointsintheinterior,thelinesegmentjoiningthemisalsointheinterior.编辑pptRectangles,CurvesandCurvedSurfaces

voidglRect{sifd}(TYPEx1,TYPEy1,TYPEx2,TYPEy2);编辑pptSpecifyingVerticesvoidglVertex{234}{sifd}[v](TYPEcoords);CallstoglVertex*()areonlyeffectivebetweenaglBegin()andglEnd()pair.编辑pptOpenGL的几何绘图图元编辑pptSpecifyingVertexList编辑pptExample1Example2-4:OtherConstructsbetweenglBegin()andglEnd()#definePI3.1415926535898GLintcircle_points=100;glBegin(GL_LINE_LOOP);for(i=0;i<circle_points;i++){angle=2*PI*i/circle_points;glVertex2f(cos(angle),sin(angle));}glEnd();编辑pptExample2glBegin(GL_POINTS);glColor3f(0.0,1.0,0.0);/*green*/glColor3f(1.0,0.0,0.0);/*red*/glVertex(...);glColor3f(1.0,1.0,0.0);/*yellow*/glColor3f(0.0,0.0,1.0);/*blue*/glVertex(...);glVertex(...);glEnd();编辑pptBasicStateManagement

Bydefault,mostofthesestatesareinitiallyinactive.Toturnonandoffmanyofthesestates,usethesetwosimplecommands:voidglEnable(GLenumcap);voidglDisable(GLenumcap);Youcanalsocheckifastateiscurrentlyenabledordisabled.GLbooleanglIsEnabled(GLenumcapability)编辑pptThereare5queryingroutinesusedto

findoutwhatvaluesaresetformanystates

voidglGetBooleanv(GLenumpname,GLboolean*params);voidglGetIntegerv(GLenumpname,GLint*params);voidglGetFloatv(GLenumpname,GLfloat*params);voidglGetDoublev(GLenumpname,GLdouble*params);voidglGetPointerv(GLenumpname,GLvoid**params);additional16queryingroutines编辑pptDisplayingPoints,Lines,andPolygons

Bydefault,apointisdrawnasasinglepixelonthescreen,alineisdrawnsolidandonepixelwide,andpolygonsaredrawnsolidlyfilledin.编辑pptPointDetails

voidglPointSize(GLfloatsize);ifthewidthis1.0,thesquareis1pixelby1pixel;ifthewidthis2.0,thesquareis2pixelsby2pixels,andsoon.Withantialiasingenabled,acirculargroupofpixelsisdrawn,andthepixelsontheboundariesaretypicallydrawnatlessthanfullintensitytogivetheedgeasmootherappearance.Inthismode,non-integerwidthsaren'trounded.编辑pptLineDetails

WideLinesvoidglLineWidth(GLfloatwidth);StippledLinesTomakestippled(dottedordashed)lines,youusethecommandglLineStipple()todefinethestipplepattern,andthenyouenablelinestipplingwithglEnable().voidglLineStipple(GLintfactor,GLushortpattern);glLineStipple(1,0x3F07);glEnable(GL_LINE_STIPPLE);Ifthisseemsbackward,rememberthatthelow-orderbitisusedfirst.编辑pptStippleLineexampleRunLines.cprogram编辑pptPolygonsasPoints,Outlines,orSolidsvoidglPolygonMode(GLenumface,GLenummode);glPolygonMode(GL_FRONT,GL_FILL);glPolygonMode(GL_BACK,GL_LINE);voidglFrontFace(GLenummode);voidglCullFace(GLenummode);编辑pptStipplingPolygons

voidglPolygonStipple(constGLubyte*mask);Definesthecurrentstipplepatternforfilledpolygons.Theargumentmaskisapointertoa32×32bitmapthat'sinterpretedasamaskof0sand1s.Wherea1appears,thecorrespondingpixelinthepolygonisdrawn,andwherea0appears,nothingisdrawn.polys.c编辑pptMarkingPolygonBoundaryEdges

Example2-7:MarkingPolygonBoundaryEdgesglPolygonMode(GL_FRONT_AND_BACK,GL_LINE);glBegin(GL_POLYGON);glEdgeFlag(GL_TRUE);glVertex3fv(V0);glEdgeFlag(GL_FALSE);glVertex3fv(V1);glEdgeFlag(GL_TRUE);glVertex3fv(V2);glEnd();编辑pptNormalVectors

Anormalvector(ornormal,forshort)isavectorthatpointsinadirectionthat'sperpendiculartoasurface.Anobject'snormalvectorsdefinetheorientationofitssurfaceinspacevoidglNormal3{bsidf}(TYPEnx,TYPEny,TYPEnz);Theb,s,andiversionsscaletheirparametervalueslinearlytotherange[-1.0,1.0].编辑pptVertexArraysOpenGLhasvertexarrayroutinesthatallowyoutospecifyalotofvertex-relateddatawithjustafewarraysandtoaccessthatdatawithequallyfewfunctioncalls.编辑pptStep1.EnablingArrays

voidglEnableClientState(GLenumarray)voidglDisableClientState(GLenumarray);编辑pptStep2.SpecifyingDatafortheArrays

voidglVertexPointer(GLintsize,GLenumtype,GLsizeistride,constGLvoid*pointer);voidglColorPointer(GLintsize,GLenumtype,GLsizeistride,constGLvoid*pointer);voidglIndexPointer(GLenumtype,GLsizeistride,constGLvoid*pointer);voidglNormalPointer(GLenumtype,GLsizeistride,constGLvoid*pointer);voidglTexCoordPointer(GLintsize,GLenumtype,GLsizeistride,constGLvoid*pointer);voidglEdgeFlagPointer(GLsizeistride,constGLvoid*pointer);编辑pptStep3:DereferencingandRendering

voidglArrayElement(GLintith)voidglDrawElements(GLenummode,GLsizeicount,GLenumtype,void*indices);voidglDrawArrays(GLenummode,GLintfirst,GLsizeicount);voidglInterleavedArrays(GLenumformat,GLsizeistride,void*pointer)编辑pptAttributeGroups

voidglPushAttrib(GLbitfieldmask);voidglPopAttrib(void);编辑pptChapter3

Viewing编辑pptTakeaphoto编辑pptTransformationPipeline编辑pptTransformation在内存中存贮的顺序为若按照列向量进行运算的话，在内存中存贮的顺序是先列后行。编辑ppt变换过程Theviewingandmodelingtransformationsyouspecifyarecombinedtoformthemodelviewmatrix,编辑pptAsimpletransformationCube.c编辑pptViewingTransformationpositioningandaimingacamera编辑pptTheModelingTransformationYouusethemodelingtransformationtopositionandorientthemodel.

glScale,glRotate,glTranslate编辑pptModelViewmatrixNotethatinsteadofmovingthecamera(withaviewingtransformation)sothatthecubecouldbeviewed,youcouldhavemovedthecubeawayfromthecamera(withamodelingtransformation).

编辑pptTheProjectionTransformation

Specifyingtheprojectiontransformationislikechoosingalensforacamera.Choosingamongwide-angle,normal,andtelephotolensesPerspectiveprojection

gluPerspective(fovy,aspect,near,far)glFrustumOrthographicprojection

glOrtho(GLdoubleleft,GLdoubleright,GLdoublebottom,GLdoubletop,GLdoublenear,GLdoublefar)编辑pptTheViewportTransformationtheprojectiontransformationandtheviewporttransformationdeterminehowascenegetsmappedontothecomputerscreen.Theprojectiontransformationspecifiesthemechanicsofhowthemappingshouldoccur,andtheviewportindicatestheshapeoftheavailablescreenareaintowhichthesceneismapped.编辑ppt视点坐标系、归一化的设备坐标系、屏幕坐标系投影变换和除法视图变换编辑ppt如何看待模型变换（1）glMatrixMode(GL_MODELVIEW);glLoadIdentity();glMultMatrixf(N);/*applytransformationN*/glMultMatrixf(M);/*applytransformationM*/glMultMatrixf(L);/*applytransformationL*/glBegin(GL_POINTS);glVertex3f(v);/*drawtransformedvertexv*/glEnd();变换顺序非常重要当前的矩阵起作用编辑ppt如何看待模型变换（2）全局固定坐标系统Matrixmultiplicationsaffecttheposition,orientation,andscalingofyourmodel-youhavetothinkofthemultiplicationsasoccurringintheoppositeorderfromhowtheyappearinthecode.glMatrixMode(GL_MODELVIEW);glLoadIdentity();glMultMatrixf(T);/*translation*/glMultMatrixf(R);/*rotation*/draw_the_object();编辑ppt如何看待模型变换（3）移动坐标系统Alocalcoordinatesystemistiedtotheobjectyou'redrawing.Alloperationsoccurrelativetothischangingcoordinatesystem.Withthisapproach,thematrixmultiplicationsnowappearinthenaturalorderinthecode.glMatrixMode(GL_MODELVIEW);glLoadIdentity();glMultMatrixf(T);/*translation*/glMultMatrixf(R);/*rotation*/draw_the_object();编辑pptModelingTransformationsTransformanobjectbymoving,rotating,stretching,shrinking,orreflectingit.Allthreecommandsareequivalenttoproducinganappropriatetranslation,rotation,orscalingmatrix,andthencallingglMultMatrix*()withthatmatrixastheargument.voidglTranslate{fd}(TYPEx,TYPEy,TYPEz);voidglRotate{fd}(TYPEangle,TYPEx,TYPEy,TYPEz);voidglScale{fd}(TYPEx,TYPEy,TYPEz);编辑pptModelingTransformationExamplemodel.c编辑pptViewingTransformationsAviewingtransformationchangesthepositionandorientationoftheviewpoint.theviewingtransformationpositionsthecameratripod,pointingthecameratowardthemodel.UsingthreewaystomakeviewingtransformationglRotateandglTranslategluLookAt()Createyourownutilityroutinethatencapsulatesrotationsandtranslations编辑pptUsingglTranslateandglRotatetosetviewingtransformationInthesimplestcase,youcanmovetheviewpointbackward,awayfromtheobjects;thishasthesameeffectasmovingtheobjectsforward,orawayfromtheviewpoint.操作照相机，相当于模型空间作相应的逆变换。编辑pptUsingthegluLookAt()UtilityRoutinegluLookAt(cx,cy,cz,rx,ry,rz,ux,uy,uz)编辑pptCreatingaCustomUtilityRoutinevoidpilotView{GLdoubleplanex,GLdoubleplaney,GLdoubleplanez,GLdoubleroll,GLdoublepitch,GLdoubleheading){glRotated(-roll,0.0,0.0,1.0);glRotated(-pitch,0.0,1.0,0.0);glRotated(-heading,1.0,0.0,0.0);glTranslated(-planex,-planey,-planez);}编辑pptPerspectiveProjectiontransformationsvoidglFrustum(GLdoubleleft,GLdoubleright,GLdoublebottom,GLdoubletop,GLdoublenear,GLdoublefar);voidgluPerspective(GLdoublefovy,GLdoubleaspect,GLdoublenear,GLdoublefar);编辑pptOrthographicProjectionvoidglOrtho(GLdoubleleft,GLdoubleright,GLdoublebottom,GLdoubletop,GLdoublenear,GLdoublefar);编辑pptViewportTransformationvoidglViewport(GLintx,GLinty,GLsizeiwidth,GLsizeiheight);编辑pptManipulatingtheMatrixStacks

glMatrixMode(GL_MODELVIEW)glMatrixMode(GL_PROJECTION)编辑ppt矩阵堆栈的操作函数glMatrixMode(….)glPushMatrix();glMultiMatrix(M);glPopMatrix();glLoadMatrix(M);voidglRotate{fd}(TYPEangle,TYPEx,TYPEy,TYPEz);glTranslatef(Tx,Ty,Tz);glScalef(Sx,Sy,Sz);编辑ppt矩阵堆栈操作的原则首先要明确对那个堆栈操作只有堆栈的栈顶矩阵起作用glScale,glRotate,gluLookAt,gluPerspective,glTranslate等都是默认对原来的栈顶矩阵乘上该矩阵若把顶点看成行向量，则矩阵相乘都是左乘。若把顶点看成列向量，则矩阵相乘都是右乘。编辑pptAdditionalClippingPlanes编辑pptvoidglClipPlane(GLenumplane,constGLdouble*equation);

Definesaclippingplane.Theequationargumentpointstothefourcoefficientsoftheplaneequation,Ax+By+Cz+D=0.Allpointswitheyecoordinates(xe,ye,ze,we)thatsatisfy(ABCD)M-1(xeyezewe)T>=0lieinthehalf-spacedefinedbytheplane,whereMisthecurrentmodelviewmatrixatthetimeglClipPlane()iscalled.Allpointsnotinthishalf-spaceareclippedaway.TheplaneargumentisGL_CLIP_PLANEi,whereiisanintegerspecifyingwhichoftheavailableclippingplanestodefine.iisanumberbetween0andonelessthanthemaximumnumberofadditionalclippingplanes.glEnable(GL_CLIP_PLANEi);编辑pptReversingTransformations

intgluUnProject(GLdoublewinx,GLdoublewiny,GLdoublewinz,constGLdoublemodelMatrix[16],constGLdoubleprojMatrix[16],constGLintviewport[4],GLdouble*objx,GLdouble*objy,GLdouble*objz);Mapthespecifiedwindowcoordinates(winx,winy,winz)intoobjectcoordinates,usingtransformationsdefinedbyamodelviewmatrix(modelMatrix),projectionmatrix(projMatrix),andviewport(viewport).编辑pptMimickingTransformationsintgluProject(GLdoubleobjx,GLdoubleobjy,GLdoubleobjz,constGLdoublemodelMatrix[16],constGLdoubleprojMatrix[16],constGLintviewport[4],GLdouble*winx,GLdouble*winy,GLdouble*winz);编辑ppt矩阵与空间转换的总结必须明确当前所在的空间。比较明确的空间是：标准屏幕空间。[-1,1]x[-1,1]x[-1,1]。视点空间（以视点为原点的空间）。模型空间—模型所在的空间。标准的屏幕坐标是固定的。模型空间是经常变化的。把变换分成两个阶段来考虑，分别对应两个矩阵堆栈，projection堆栈和modelview堆栈。Projection堆栈对应一个透视或正交变换。Modelview堆栈对应是把模型变换到视点空间的变换。所以在编程时要分开处理。ModelView变换是比较复杂的，它是把模型从局部空间变换到视点空间。也就是说当你发起glVertex命令的时候，必须明白当前在那个空间中。编辑ppt具体解释robot例子程序编辑pptChapter4Color

编辑pptDithering

Somegraphicshardwareusesditheringtoincreasethenumberofapparentcolors.Ditheringisthetechniqueofusingcombinationsofsomecolorstocreatetheeffectofothercolors.编辑pptColor-IndexDisplayMode

编辑pptSpecifyingaColorinRGBAMode

voidglColor3{bsifdubusui}(TYPEr,TYPEg,TYPEb);voidglColor4{bsifdubusui}(TYPEr,TYPEg,TYPEb,TYPEa);voidglColor3{bsifdubusui}v(constTYPE*v);voidglColor4{bsifdubusui}v(constTYPE*v);编辑pptSpecifyingaColorinColor-IndexMode

voidglIndex{sifdub}(TYPEc);voidglIndex{sifdub}v(constTYPE*c);Setsthecurrentcolorindextoc.Thefirstsuffixforthiscommandindicatesthedatatypeforparameters:short,integer,float,double,orunsignedbyte.Thesecond,optionalsuffixisv,whichindicatesthattheargumentisanarrayofvaluesofthegivendatatype(thearraycontainsonlyonevalue).编辑pptSpecifyingaShadingModel

voidglShadeModel(GLenummode);Setstheshadingmodel.ThemodeparametercanbeeitherGL_SMOOTH(thedefault)orGL_FLAT.编辑pptFlat-ShadedPolygon编辑pptChapter5Lighting

编辑pptAHidden-SurfaceRemovalSurvivalKitglEnable(GL_DEPTH_TEST);...while(1){glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);get_viewing_point_from_mouse_position();draw_3d_object_A();draw_3d_object_B();}编辑pptReal-WorldandOpenGLLightingOpenGLapproximateslightandlightingasiflightcanbebrokenintored,green,andbluecomponents.TheOpenGLlightingmodelconsidersthelightingtobedividedintofourindependentcomponents:emissive,ambient,diffuse,andspecular.Allfourcomponentsarecomputedindependentlyandthenaddedtogether.编辑pptAmbient,Diffuse,andSpecularLight

Ambientilluminationislightthat'sbeenscatteredsomuchbytheenvironmentthatitsdirectionisimpossibletodetermine-itseemstocomefromalldirections.Thediffusecomponentisthelightthatcomesfromonedirection,soit'sbrighterifitcomessquarelydownonasurfacethanifitbarelyglancesoffthesurface.specularlightcomesfromaparticulardirection,andittendstobounceoffthesurfaceinapreferreddirection.编辑pptMaterialColors

TheOpenGLlightingmodelmakestheapproximationthatamaterial'scolordependsonthepercentagesoftheincomingred,green,andbluelightitreflects.Materialshavedifferentambient,diffuse,andspecularcolors,whichdeterminetheambient,diffuse,andspecularreflectancesofthematerial.Amaterial'sambientreflectanceiscombinedwiththeambientcomponentofeachincominglightsourceAmbientanddiffusereflectancesdefinethecolorofthematerialandaretypicallysimilarifnotidentical.Specularreflectanceisusuallywhiteorgray,sothatspecularhighlightsendupbeingthecolorofthelightsource'sspecularintensity.Ifyouthinkofawhitelightshiningonashinyredplasticsphere,mostofthesphereappearsred,buttheshinyhighlightiswhite.emissivecolordoesnotintroduceanyadditionallightintotheoverallscene编辑pptRGBValuesforLightsandMaterials

Foralight,thenumberscorrespondtoapercentageoffullintensityforeachcolor.Formaterials,thenumberscorrespondtothereflectedproportionsofthosecolors.ifanOpenGLlighthascomponents(LR,LG,LB),andamaterialhascorrespondingcomponents(MR,MG,MB),then,ignoringallotherreflectivityeffects,thelightthatarrivesattheeyeisgivenby(LR*MR,LG*MG,LB*MB).编辑pptASimpleExample:RenderingaLitSphere

Definenormalvectorsforeachvertexofalltheobjects.Thesenormalsdeterminetheorientationoftheobjectrelativetothelightsources.Create,select,andpositiononeormorelightsources.Createandselectalightingmodel,whichdefinesthelevelofglobalambientlightandtheeffectivelocationoftheviewpoint(forthepurposesoflightingcalculations).Definematerialpropertiesfortheobjectsinthescene.编辑pptCreatingLightSourcesvoidglLight{if}(GLenumlight,GLenumpname,TYPEparam);voidglLight{if}v(GLenumlight,GLenumpname,TYPE*param);Createsthelightspecifiedbylight,whichcanbeGL_LIGHT0,GL_LIGHT1,...,orGL_LIGHT7.编辑pptDefaultValuesforpnameParameterofglLight*()编辑pptLightPositiondirectionallightsourceGLfloatlight_position[]={1.0,1.0,1.0,0.0};glLightfv(GL_LIGHT0,GL_POSITION,light_position);

positionallightsourceGLfloatlight_position[]={1.0,1.0,1.0,1.0};glLightfv(GL_LIGHT0,GL_POSITION,light_position);编辑pptAttenuationSinceadirectionallightisinfinitelyfaraway,itdoesn'tmakesensetoattenuateitsintensityoverdistance,soattenuationisdisabledforadirectionallight.However,youmightwanttoattenuatethelightfromapositionallight.OpenGLattenuatesalightsourcebymultiplyingthecontributionofthatsourcebyanattenuationfactor:whered=distancebetweenthelight'spositionandthevertexkc=GL_CONSTANT_ATTENUATIONkl=GL_LINEAR_ATTENUATIONkq=GL_QUADRATIC_ATTENUATION编辑pptSpotlights

编辑pptSpotlightfunctionGL_SPOT_CUTOFFisrestrictedtobeingwithintherange[0.0,90.0](unlessithasthespecialvalue180.0).glLightf(GL_LIGHT0,GL_SPOT_CUTOFF,45.0);Youalsoneedtospecifyaspotlight'sdirection,whichdeterminestheaxisoftheconeoflight:GLfloatspot_direction[]={-1.0,-1.0,0.0};glLightfv(GL_LIGHT0,GL_SPOT_DIRECTION,spot_direction);Bydefault,thedirectionis(0.0,0.0,-1.0),Also,keepinmindthataspotlight'sdirectionistransformedbythemodelviewmatrixjustasthoughitwereanormalvector,andtheresultisstoredineyecoordinates.settheGL_SPOT_EXPONENTparameter,whichbydefaultiszero,tocontrolhowconcentratedthelightis.Thelight'sintensityishighestinthecenterofthecone.It'sattenuatedtowardtheedgesoftheconebythecosineoftheanglebetweenthedirectionofthelightandthedirectionfromthelighttothevertexbeinglit.编辑pptMultipleLightsGLfloatlight1_ambient[]={0.2,0.2,0.2,1.0};GLfloatlight1_diffuse[]={1.0,1.0,1.0,1.0};GLfloatlight1_specular[]={1.0,1.0,1.0,1.0};GLfloatlight1_position[]={-2.0,2.0,1.0,1.0};GLfloatspot_direction[]={-1.0,-1.0,0.0};glLightfv(GL_LIGHT1,GL_AMBIENT,light1_ambient);glLightfv(GL_LIGHT1,GL_DIFFUSE,light1_diffuse);glLightfv(GL_LIGHT1,GL_SPECULAR,light1_specular);glLightfv(GL_LIGHT1,GL_POSITION,light1_position);glLightf(GL_LIGHT1,GL_CONSTANT_ATTENUATION,1.5);glLightf(GL_LIGHT1,GL_LINEAR_ATTENUATION,0.5);glLightf(GL_LIGHT1,GL_QUADRATIC_ATTENUATION,0.2);glLightf(GL_LIGHT1,GL_SPOT_CUTOFF,45.0);glLightfv(GL_LIGHT1,GL_SPOT_DIRECTION,spot_direction);glLightf(GL_LIGHT1,GL_SPOT_EXPONENT,2.0);glEnable(GL_LIGHT1);编辑pptControllingaLight'sPositionandDirectionOpenGLtreatsthepositionanddirectionofalightsourcejustasittreatsthepositionofageometricprimitive.whenglLight*()iscalledtospecifythepositionorthedirectionofalightsource,thepositionordirectionistransformedbythecurrentmodelviewmatrixandstoredineyecoordinates.编辑pptKeepingtheLightStationaryglViewport(0,0,(GLsizei)w,(GLsizei)h);glMatrixMode(GL_PROJECTION);glLoadIdentity();if(w<=h)glOrtho(-1.5,1.5,-1.5*h/w,1.5*h/w,-10.0,10.0);elseglOrtho(-1.5*w/h,1.5*w/h,-1.5,1.5,-10.0,10.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();/*laterininit()*/GLfloatlight_position[]={1.0,1.0,1.0,1.0};glLightfv(GL_LIGHT0,GL_POSITION,position);编辑pptIndependentlyMovingtheLightrotateortranslatethelightpositionsothatthelightmovesrelativetoastationaryobjectstaticGLdoublespin;voiddisplay(void){GLfloatlight_position[]={0.0,0.0,1.5,1.0};glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);glPushMatrix();gluLookAt(0.0,0.0,5.0,0.0,0.0,0.0,0.0,1.0,0.0);glPushMatrix();glRotated(spin,1.0,0.0,0.0);glLightfv(GL_LIGHT0,GL_POSITION,light_position);glPopMatrix();glutSolidTorus(0.275,0.85,8,15);glPopMatrix();glFlush();}编辑pptMovingtheLightSourceTogetherwithYourViewpoint(miner'shat)GLfloatlight_position()={0.0,0.0,0.0,1.0};glViewport(0,0,(GLint)w,(GLint)h);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(40.0,(GLfloat)w/(GLfloat)h,1.0,100.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();glLightfv(GL_LIGHT0,GL_POSITION,light_position);编辑pptSelectingaLightingModelTheOpenGLnotionofalightingmodelhasthreecomponents:TheglobalambientlightintensityWhethertheviewpointpositionislocaltothesceneorwhetheritshouldbeconsideredtobeaninfinitedistanceawayWhetherlightingcalculationsshouldbeperformeddifferentlyforboththefrontandbackfacesofobjects编辑pptglLightModelvoidglLightModel{if}(GLenumpname,TYPEparam);voidglLightModel{if}v(GLenumpname,TYPE*param);编辑pptGlobalAmbientLight

GLfloatlmodel_ambient[]={0.2,0.2,0.2,1.0};glLightModelfv(GL_LIGHT_MODEL_AMBIENT,lmodel_ambient);evenifyoudon'taddaspecificlightsourcetoyourscene,youcanstillseetheobjectsinthescene.编辑pptLocalorInfiniteViewpointThelocationoftheviewpointaffectsthecalculationsforhighlightsproducedbyspecularreflectance.glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER,GL_TRUE);Thiscallplacestheviewpointat(0,0,0)ineyecoordinates.Toswitchbacktoaninfiniteviewpoint,passinGL_FALSEastheargument.编辑pptTwo-sidedLighting

glLightModeli(GL_LIGHT_MODEL_TWO_SIDE,GL_TRUE);编辑pptDefiningMaterialPropertiesvoidglMaterial{if}(GLenumface,GLenumpname,TYPEparam);voidglMaterial{if}v(GLenumface,GLenumpname,TYPE*param);Specifiesacurrentmaterialpropertyforuseinlightingcalculations.facecanbeGL_FRONT,GL_BACK,orGL_FRONT_AND_BACKtoindicatewhichfaceoftheobjectthematerialshouldbeappliedto.编辑ppt材料前后面定义的属性值编辑pptDiffuseandAmbientReflection

Diffusereflectanceplaysthemostimportantroleindeterminingwhatyouperceivethecolorofanobjecttobe.It'saffectedbythecoloroftheincidentdiffuselightandtheangleoftheincidentlightrelativetothenormaldirection.Thepositionoftheviewpointdoesn'taffectdif