OpenGL Frame Buffer Object (FBO) - Song Ho Ahn

Framebuffer is a collection of 2D arrays or storages utilized by OpenGL; colour buffers, depth buffer, stencil buffer and accumulation buffer. By default, ... ←Back OpenGLFrameBufferObject(FBO) RelatedTopics:PixelBufferObject(PBO) Download:fbo.zip,fboDepth.zip,fboStencil.zip,fboBlit.zip,fboMsaa.zip,FrameBuffer.zip Overview CreatingFBO RenderbufferObject FBOwithMSAA(MultiSampleAntiAliasing) CheckingFBOStatus Example:RenderToTexture FrameBufferC++Class Update:FramebufferobjectextensionispromotedasacorefeatureofOpenGLversion3.0,andisapprovedbyARBcombiningthefollowingextensions; EXT_framebuffer_object EXT_framebuffer_blit EXT_framebuffer_multisample EXT_packed_depth_stencil Overview InOpenGLrenderingpipeline,thegeometrydataandtexturesaretransformedandpassedseveraltests,andthenfinallyrenderedontoascreenas2Dpixels.ThefinalrenderingdestinationoftheOpenGLpipelineiscalledframebuffer.Framebufferisacollectionof2DarraysorstoragesutilizedbyOpenGL;colourbuffers,depthbuffer,stencilbufferandaccumulationbuffer.Bydefault,OpenGLusestheframebufferasarenderingdestinationthatiscreatedandmanagedentirelybythewindowsystem.Thisdefaultframebufferiscalledwindow-system-providedframebuffer. TheOpenGLextension,GL_ARB_framebuffer_objectprovidesaninterfacetocreateadditionalnon-displayableframebufferobjects(FBO).Thisframebufferiscalledapplication-createdframebufferinordertodistinguishfromthedefaultwindow-system-providedframebuffer.Byusingframebufferobject(FBO),anOpenGLapplicationcanredirecttherenderingoutputtotheapplication-createdframebufferobject(FBO)otherthanthetraditionalwindow-system-providedframebuffer.And,itisfullycontrolledbyOpenGL. Similartowindow-system-providedframebuffer,aFBOcontainsacollectionofrenderingdestinations;color,depthandstencilbuffer.(NotethataccumulationbufferisnotdefinedinFBO.)TheselogicalbuffersinaFBOarecalledframebuffer-attachableimages,whichare2Darraysofpixelsthatcanbeattachedtoaframebufferobject. Therearetwotypesofframebuffer-attachableimages;textureimagesandrenderbufferimages.Ifanimageofatextureobjectisattachedtoaframebuffer,OpenGLperforms"rendertotexture".Andifanimageofarenderbufferobjectisattachedtoaframebuffer,thenOpenGLperforms"offscreenrendering". Bytheway,renderbufferobjectisanewtypeofstorageobjectdefinedinGL_ARB_framebuffer_objectextension.Itisusedasarenderingdestinationforasingle2Dimageduringrenderingprocess. ConnectivitybetweenFBO,textureandRenderbuffer Thefollowingdiagramshowstheconnectivityamongtheframebufferobject,textureobjectandrenderbufferobject.Multipletextureobjectsorrenderbufferobjectscanbeattachedtoaframebufferobjectthroughtheattachmentpoints. Therearemultiplecolorattachmentpoints(GL_COLOR_ATTACHMENT0,...,GL_COLOR_ATTACHMENTn),onedepthattachmentpoint(GL_DEPTH_ATTACHMENT),andonestencilattachmentpoint(GL_STENCIL_ATTACHMENT)inaframebufferobject.Thenumberofcolorattachmentpointsisimplementationdependent,buteachFBOmusthaveatleastonecolorattachementpoint.YoucanquerythemaximumnumberofcolorattachementpointswithGL_MAX_COLOR_ATTACHMENTS,whicharesupportedbyagraphicscard.ThereasonthataFBOhasmultiplecolorattachementpointsistoallowtorenderthecolorbuffertomultipledestinationsatthesametime.This"multiplerendertargets"(MRT)canbeaccomplishedbyGL_ARB_draw_buffersextension.Noticethattheframebufferobjectitselfdoesnothaveanyimagestorage(array)init,but,ithasonlymultipleattachmentpoints. Framebufferobject(FBO)providesanefficientswitchingmechanism;detachthepreviousframebuffer-attachableimagefromaFBO,andattachanewframebuffer-attachableimagetotheFBO.Switchingframebuffer-attachableimagesismuchfasterthanswitchingbetweenFBOs.FBOprovidesglFramebufferTexture2D()toswitch2Dtextureobjects,andglFramebufferRenderbuffer()toswitchrenderbufferobjects. CreatingFrameBufferObject(FBO) Creatingframebufferobjectsissimilartogeneratingvertexbufferobjects(VBO). glGenFramebuffers() voidglGenFramebuffers(GLsizein,GLuint*ids) voidglDeleteFramebuffers(GLsizein,constGLuint*ids) glGenFramebuffers()requires2parameters;thefirstoneisthenumberofframebufferstocreate,andthesecondparameteristhepointertoaGLuintvariableoranarraytostoreasingleIDormultipleIDs.ItreturnstheIDsofunusedframebufferobjects.ID0meansthedefaultframebuffer,whichisthewindow-system-providedframebuffer. And,FBOmaybedeletedbycallingglDeleteFramebuffers()whenitisnotusedanymore. glBindFramebuffer() OnceaFBOiscreated,ithastobeboundbeforeusingit. voidglBindFramebuffer(GLenumtarget,GLuintid) Thefirstparameter,target,shouldbeGL_FRAMEBUFFER,andthesecondparameteristheIDofaframebufferobject.OnceaFBOisbound,allOpenGLoperationsaffectontothecurrentboundframebufferobject.TheobjectID0isreservedforthedefaultwindow-systemprovidedframebuffer.Therefore,inordertounbindthecurrentframebuffer(FBO),useID0inglBindFramebuffer(). RenderbufferObject Inaddition,renderbufferobjectisnewlyintroducedforoffscreenrendering.Itallowstorenderascenedirectlytoarenderbufferobject,insteadofrenderingtoatextureobject.Renderbufferissimplyadatastorageobjectcontainingasingleimageofarenderableinternalformat.ItisusedtostoreOpenGLlogicalbuffersthatdonothavecorrespondingtextureformat,suchasstencilordepthbuffer. glGenRenderbuffers() voidglGenRenderbuffers(GLsizein,GLuint*ids) voidglDeleteRenderbuffers(GLsizein,constGluint*ids) Oncearenderbufferiscreated,itreturnsnon-zeropositiveinteger.ID0isreservedforOpenGL. glBindRenderbuffer() voidglBindRenderbuffer(GLenumtarget,GLuintid) SameasotherOpenGLobjects,youhavetobindthecurrentrenderbufferobjectbeforereferencingit.ThetargetparametershouldbeGL_RENDERBUFFERforrenderbufferobject. glRenderbufferStorage() voidglRenderbufferStorage(GLenumtarget, GLenuminternalFormat, GLsizeiwidth, GLsizeiheight) Whenarenderbufferobjectiscreated,itdoesnothaveanydatastorage,sowehavetoallocateamemoryspaceforit.ThiscanbedonebyusingglRenderbufferStorage().ThefirstparametermustbeGL_RENDERBUFFER.Thesecondparameterwouldbecolor-renderable(GL_RGB,GL_RGBA,etc.),depth-renderable(GL_DEPTH_COMPONENT),orstencil-renderableformats(GL_STENCIL_INDEX).Thewidthandheightarethedimensionoftherenderbufferimageinpixels. ThewidthandheightshouldbelessthanGL_MAX_RENDERBUFFER_SIZE,otherwise,itgeneratesGL_INVALID_VALUEerror. glGetRenderbufferParameteriv() voidglGetRenderbufferParameteriv(GLenumtarget, GLenumparam, GLint*value) Youalsogetvariousparametersofthecurrentlyboundrenderbufferobject.targetshouldbeGL_RENDERBUFFER,andthesecondparameteristhenameofparameter.Thelastisthepointertoanintegervariabletostorethereturnedvalue.Theavailablenamesoftherenderbufferparametersare; GL_RENDERBUFFER_WIDTH GL_RENDERBUFFER_HEIGHT GL_RENDERBUFFER_INTERNAL_FORMAT GL_RENDERBUFFER_RED_SIZE GL_RENDERBUFFER_GREEN_SIZE GL_RENDERBUFFER_BLUE_SIZE GL_RENDERBUFFER_ALPHA_SIZE GL_RENDERBUFFER_DEPTH_SIZE GL_RENDERBUFFER_STENCIL_SIZE AttachingimagestoFBO FBOitselfdoesnothaveanyimagestorage(buffer)init.Instead,wemustattachframebuffer-attachableimages(textureorrenderbufferobjects)totheFBO.ThismechanismallowsthatFBOquicklyswitch(detachandattach)theframebuffer-attachableimagesinaFBO.Itismuchfastertoswitchframebuffer-attachableimagesthantoswitchbetweenFBOs.And,itsavesunnecessarydatacopiesandmemoryconsumption.Forexample,atexturecanbeattachedtomultipleFBOs,anditsimagestoragecanbesharedbymultipleFBOs. Attachinga2DtextureimagetoFBO glFramebufferTexture2D(GLenumtarget, GLenumattachmentPoint, GLenumtextureTarget, GLuinttextureId, GLintlevel) glFramebufferTexture2D()istoattacha2DtextureimagetoaFBO.ThefirstparametermustbeGL_FRAMEBUFFER,andthesecondparameteristheattachmentpointwheretoconnectthetextureimage.AFBOhasmultiplecolorattachmentpoints(GL_COLOR_ATTACHMENT0,...,GL_COLOR_ATTACHMENTn),GL_DEPTH_ATTACHMENT,andGL_STENCIL_ATTACHMENT.Thethirdparameter,"textureTarget"isGL_TEXTURE_2Dinmostcases.Thefourthparameteristheidentifierofthetextureobject.Thelastparameteristhemipmaplevelofthetexturetobeattached. IfthetextureIdparameterissetto0,then,thetextureimagewillbedetachedfromtheFBO.IfatextureobjectisdeletedwhileitisstillattachedtoaFBO,then,thetextureimagewillbeautomaticallydetachedfromthecurrentlyboundFBO.However,ifitisattachedtomultipleFBOsanddeleted,thenitwillbedetachedfromonlytheboundFBO,butwillnotbedetachedfromanyotherun-boundFBOs. AttachingaRenderbufferimagetoFBO voidglFramebufferRenderbuffer(GLenumtarget, GLenumattachmentPoint, GLenumrenderbufferTarget, GLuintrenderbufferId) ArenderbufferimagecanbeattachedbycallingglFramebufferRenderbuffer().ThefirstandsecondparametersaresameasglFramebufferTexture2D().ThethirdparametermustbeGL_RENDERBUFFER,andthelastparameteristheIDoftherenderbufferobject. IfrenderbufferIdparameterissetto0,therenderbufferimagewillbedetachedfromtheattachmentpointintheFBO.IfarenderbufferobjectisdeletedwhileitisstillattachedinaFBO,thenitwillbeautomaticallydetachedfromtheboundFBO.However,itwillnotbedetachedfromanyothernon-boundFBOs. FBOwithMSAA(MultiSampleAntiAliasing) Comparison:NoAnti-aliasingvs.MSAA WhenyourendertoaFBO,anti-aliasingisnotautomaticallyenabledevenifyouproperlycreateaOpenGLrenderingcontextwiththemultisamplingattribute(SAMPLEBUFFERS_ARB)forwindow-system-providedframebuffer. Inordertoactivatemultisampleanti-aliasingmodeforrenderingtoaFBO,youneedtoprepareandattachmultisampleimagestoaFBO'scolorand/ordepthattachementpoints. FBOextensionprovidesglRenderbufferStorageMultisample()tocreatearenderbufferimageformultisampleanti-aliasingrenderingmode. voidglRenderbufferStorageMultisample(GLenumtarget, GLsizeisamples, GLenuminternalFormat, GLsizeiwidth, GLsizeiheight) Itaddsnewparameter,samplesontopofglRenderbufferStorage(),whichisthenumberofmultisamplesforanti-aliasedrenderingmode.Ifitis0,thennoMSAAmodeisenabledandglRenderbufferStorage()iscalledinstead.YoucanquerythemaximumnumberofsampleswithGL_MAX_SAMPLEStokeninglGetIntegerv(). ThefollowingcodeistocreateaFBOwithmultisamplecolorbufferanddepthbufferimages.NotethatifmultipleimagesareattachedtoaFBO,thenallimagesmusthavethesamenumberofmultisamples.Otherwise,theFBOstatusisincomplete. //createa4xMSAArenderbufferobjectforcolorbuffer intmsaa=4; GLuintrboColorId; glGenRenderbuffers(1,&rboColorId); glBindRenderbuffer(GL_RENDERBUFFER,rboColorId); glRenderbufferStorageMultisample(GL_RENDERBUFFER,msaa,GL_RGBA8,width,height); //createa4xMSAArenderbufferobjectfordepthbuffer GLuintrboDepthId; glGenRenderbuffers(1,&rboDepthId); glBindRenderbuffer(GL_RENDERBUFFER,rboDepthId); glRenderbufferStorageMultisample(GL_RENDERBUFFER,msaa,GL_DEPTH_COMPONENT,width,height); //createa4xMSAAframebufferobject GLuintfboMsaaId; glGenFramebuffers(1,&fboMsaaId); glBindFramebuffer(GL_FRAMEBUFFER,fboMsaaId); //attachcolorbufferimagetoFBO glFramebufferRenderbuffer(GL_FRAMEBUFFER,//1.fbotarget:GL_FRAMEBUFFER GL_COLOR_ATTACHMENT0,//2.colorattachmentpoint GL_RENDERBUFFER,//3.rbotarget:GL_RENDERBUFFER rboColorId);//4.rboID //attachdepthbufferimagetoFBO glFramebufferRenderbuffer(GL_FRAMEBUFFER,//1.fbotarget:GL_FRAMEBUFFER GL_DEPTH_ATTACHMENT,//2.depthattachmentpoint GL_RENDERBUFFER,//3.rbotarget:GL_RENDERBUFFER rboDepthId);//4.rboID //checkFBOstatus GLenumstatus=glCheckFramebufferStatus(GL_FRAMEBUFFER); if(status!=GL_FRAMEBUFFER_COMPLETE) fboUsed=false; ItisimportanttoknowthatglRenderbufferStorageMultisample()onlyenablesMSAArenderingtoFBO.However,youcannotdirectlyusetheresultfromMSAAFBO.Ifyouneedtotransfertheresulttoatextureorothernon-multisampledframebuffer,youhavetoconvert(downsample)theresulttosingle-sampleimageusingglBlitFramebuffer(). voidglBlitFramebuffer(GLintsrcX0,GLintsrcY0,GLintsrcX1,GLintsrcY1,//sourcerectangle GLintdstX0,GLintdstY0,GLintdstX1,GLintdstY1,//destinationrect GLbitfieldmask, GLenumfilter) glBlitFramebuffer()copiesarectangleofimagesfromthesource(GL_READ_BUFFER)tothedestinationframebuffer(GL_DRAW_BUFFER).The"mask"parameteristospecifywhichbuffersarecopied,GL_COLOR_BUFFER_BIT,GL_DEPTH_BUFFER_BITand/orGL_STENCIL_BUFFER_BIT.Thelastparameter,"filter"istospecifytheinterpolationmodeifthesourceanddestinationrectanglesarenotsamedimension.ItiseitherGL_NEARESTorGL_LINEAR. ThefollowingcodeistotransferamultisampledimagefromaFBOtoanothernon-multisampledFBO.NoticeitrequiresanadditionalFBOtogettheresultofMSAArendering.PleaseseefboMsaa.zipfordetailstoperformrender-to-texturewithMSAA. //copyrenderedimagefromMSAA(multi-sample)tonormal(single-sample) //NOTE:Themultisamplesatapixelinreadbufferwillbeconverted //toasinglesampleatthetargetpixelindrawbuffer. glBindFramebuffer(GL_READ_FRAMEBUFFER,fboMsaaId);//srcFBO(multi-sample) glBindFramebuffer(GL_DRAW_FRAMEBUFFER,fboId);//dstFBO(single-sample) glBlitFramebuffer(0,0,width,height,//srcrect 0,0,width,height,//dstrect GL_COLOR_BUFFER_BIT,//buffermask GL_LINEAR);//scalefilter CheckingFBOStatus Onceattachableimages(texturesandrenderbuffers)areattachedtoaFBOandbeforeperformingFBOoperation,youmustvalidateiftheFBOstatusiscompleteorincompletebyusingglCheckFramebufferStatus().IftheFBOisnotcomplete,thenanydrawingandreadingcommand(glBegin(),glCopyTexImage2D(),etc)willbefailed. GLenumglCheckFramebufferStatus(GLenumtarget) glCheckFramebufferStatus()validatesallitsattachedimagesandframebufferparametersonthecurrentlyboundFBO.And,thisfunctioncannotbecalledwithinglBegin()/glEnd()pair.ThetargetparametershouldbeGL_FRAMEBUFFER.Itreturnsnon-zerovalueaftercheckingtheFBO.Ifallrequirementsandrulesaresatisfied,thenitreturnsGL_FRAMEBUFFER_COMPLETE.Otherwise,itreturnsarelevanterrorvalue,whichtellswhatruleisviolated. TherulesofFBOcompletenessare: Thewidthandheightofframebuffer-attachableimagemustbenotzero. Ifanimageisattachedtoacolorattachmentpoint,thentheimagemusthaveacolor-renderableinternalformat.(GL_RGBA,GL_DEPTH_COMPONENT,GL_LUMINANCE,etc) IfanimageisattachedtoGL_DEPTH_ATTACHMENT,thentheimagemusthaveadepth-renderableinternalformat.(GL_DEPTH_COMPONENT,GL_DEPTH_COMPONENT24,etc) IfanimageisattachedtoGL_STENCIL_ATTACHMENT,thentheimagemusthaveastencil-renderableinternalformat.(GL_STENCIL_INDEX,GL_STENCIL_INDEX8,etc) FBOmusthaveatleastoneimageattached. AllimagesattachedaFBOmusthavethesamewidthandheight. Allimagesattachedthecolorattachmentpointsmusthavethesameinternalformat. Notethateventhoughalloftheaboveconditionsaresatisfied,yourOpenGLdrivermaynotsupportsomecombinationsofinternalformatsandparameters.IfaparticularimplementationisnotsupportedbyOpenGLdriver,thenglCheckFramebufferStatus()returnsGL_FRAMEBUFFER_UNSUPPORTED. ThesamplecodeprovidessomeutilityfunctionstoreporttheinformationofthecurrentFBO;printFramebufferInfo()andcheckFramebufferStatus(). Example:RenderToTexture Downloadthesourceandbinary:fbo.zip(Updated:2020-05-07) Extras: -Renderingtothedepthbufferonly:fboDepth.zip -Renderingtheoutlinesofanobjectusingstencilbuffer:fboStencil.zip -Blitingbetween2FBOsusingglBlitFramebuffer():fboBlit.zip -RenderingtotexturewithMSAA:fboMsaa.zip -RenderingtotexturewithFrameBufferC++class:FrameBuffer.zip(Updated:2022-05-22) Sometimes,youneedtogeneratedynamictexturesonthefly.Themostcommonexamplesaregeneratingmirroring/reflectioneffects,dynamiccube/environmentmapsandshadowmaps.Dynamictexturingcanbeaccomplishedbyrenderingthescenetoatexture.Atraditionalwayofrender-to-textureistodrawascenetotheframebufferasnormal,andthencopytheframebufferimagetoatexturebyusingglCopyTexSubImage2D(). UsingFBO,wecanrenderascenedirectlyontoatexture,sowedon'thavetousethewindow-system-providedframebufferatall.Furthermore,wecaneliminateanadditionaldatacopy(fromframebuffertotexture). Thisdemoprogramperformsrendertotextureoperationwith/withoutFBO,andcomparestheperformancedifference.Otherthanperformancegain,thereisanotheradvantageofusingFBO.Ifthetextureresolutionislargerthanthesizeoftherenderingwindowintraditionalrender-to-texturemode(withoutFBO),thentheareaoutofthewindowregionwillbeclipped.However,FBOdoesnotsufferfromthisclippingproblem.Youcancreateaframebuffer-renderableimagelargerthanthedisplaywindow. ThefollowingcodesistosetupaFBOandframebuffer-attachableimagesbeforetherenderingloopisstarted.NotethatnotonlyatextureimageisattachedtotheFBO,butalso,arenderbufferimageisattachedtothedepthattachmentpointoftheFBO.Wedonotactuallyusethisdepthbuffer,however,theFBOitselfneedsitfordepthtest.Ifwedon'tattachthisdepthrenderableimagetotheFBO,thentherenderingoutputwillbecorruptedbecauseofmissingdepthtest.IfstenciltestisalsorequiredduringFBOrendering,thenadditionalrenderbufferimageshouldbeattachedtoGL_STENCIL_ATTACHMENT. ... //createatextureobject GLuinttextureId; glGenTextures(1,&textureId); glBindTexture(GL_TEXTURE_2D,textureId); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D,GL_GENERATE_MIPMAP,GL_TRUE);//automaticmipmap glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA8,width,height,0,GL_RGBA,GL_UNSIGNED_BYTE,0); glBindTexture(GL_TEXTURE_2D,0); //createarenderbufferobjecttostoredepthinfo GLuintrboId; glGenRenderbuffers(1,&rboId); glBindRenderbuffer(GL_RENDERBUFFER,rboId); glRenderbufferStorage(GL_RENDERBUFFER,GL_DEPTH_COMPONENT,width,height); glBindRenderbuffer(GL_RENDERBUFFER,0); //createaframebufferobject GLuintfboId; glGenFramebuffers(1,&fboId); glBindFramebuffer(GL_FRAMEBUFFER,fboId); //attachthetexturetoFBOcolorattachmentpoint glFramebufferTexture2D(GL_FRAMEBUFFER,//1.fbotarget:GL_FRAMEBUFFER GL_COLOR_ATTACHMENT0,//2.attachmentpoint GL_TEXTURE_2D,//3.textarget:GL_TEXTURE_2D textureId,//4.texID 0);//5.mipmaplevel:0(base) //attachtherenderbuffertodepthattachmentpoint glFramebufferRenderbuffer(GL_FRAMEBUFFER,//1.fbotarget:GL_FRAMEBUFFER GL_DEPTH_ATTACHMENT,//2.attachmentpoint GL_RENDERBUFFER,//3.rbotarget:GL_RENDERBUFFER rboId);//4.rboID //checkFBOstatus GLenumstatus=glCheckFramebufferStatus(GL_FRAMEBUFFER); if(status!=GL_FRAMEBUFFER_COMPLETE) fboUsed=false; //switchbacktowindow-system-providedframebuffer glBindFramebuffer(GL_FRAMEBUFFER,0); ... Therenderingprocedureofrender-to-textureisalmostsameasnormaldrawing.Weonlyneedtoswitchtherenderingdestinationfromthewindow-system-providedtothenon-displayable,application-createdframebuffer(FBO). ... //setrenderingdestinationtoFBO glBindFramebuffer(GL_FRAMEBUFFER,fboId); //clearbuffers glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); //drawascenetoatexturedirectly draw(); //unbindFBO glBindFramebuffer(GL_FRAMEBUFFER,0); //triggermipmapsgenerationexplicitly //NOTE:IfGL_GENERATE_MIPMAPissettoGL_TRUE,thenglCopyTexSubImage2D() //triggersmipmapgenerationautomatically.However,thetextureattached //ontoaFBOshouldgeneratemipmapsmanuallyviaglGenerateMipmap(). glBindTexture(GL_TEXTURE_2D,textureId); glGenerateMipmap(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D,0); ... NotethatglGenerateMipmap()isalsoincludedaspartofFBOextensioninordertogeneratemipmapsexplicitlyaftermodifyingthebaseleveltextureimage.IfGL_GENERATE_MIPMAPissettoGL_TRUE,thenglTex{Sub}Image2D()andglCopyTex{Sub}Image2D()triggerautomaticmipmapgeneration(inOpenGLversion1.4orgreater).However,FBOoperationdoesnotgenerateitsmipmapsautomaticallywhenthebaseleveltextureismodifiedbecauseFBOdoesnotcallglCopyTex{Sub}Image2D()tomodifythetexture.Therefore,glGenerateMipmap()mustbeexplicitlycalledformipmapgeneration. Ifyouneedtoapostprocessingofthetexture,itispossibletocombinewithPixelBufferObject(PBO)tomodifythetextureefficiently. FrameBufferC++Class ItisanexampleofC++wrapperclasshowtoencapsulateanOpenGLframebufferobject,anditsassociatedcolorbuffer(textureobject)anddepthbuffer(renderbufferobject)intoaC++class.Italsoprovidessimplebutconvenientinterfacestocontroltheframebufferobject.ThefollowingC++codesnippetiscreationandusageofFrameBufferC++class.And,seemoredetailsinFrameBuffer.cppfile.(Updated:2022-05-22) //initializeFBOwithwidth,heightandmsaa FrameBufferfbo; fbo.init(width,height);//forsingle-sampleFBO fbo.init(width,height,msaa);//formulti-sampleFBO,msaa=2,4,8... ... //checkcompletenessanderror std::cout<