Instancing - OpenGL ES SDK for Android - GitHub Pages

This sample presents the instanced drawing technique using OpenGL ES 3.0. Overview. Instancing_android.png. Each cube is an instance of the same object. There ... OpenGLESSDKforAndroid ARMDeveloperCenter Home Pages Namespaces Files  All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Macros Pages ThissamplepresentstheinstanceddrawingtechniqueusingOpenGLES3.0. Overview Eachcubeisaninstanceofthesameobject. Thereisonlyonecopyofthecubevertexdatainmemory,andeachofthecubesdrawnisaninstanceofthatdata.ThisreducestheamountofmemorythatneedstobetransferredtotheGPU.Byusinggl_instanceIDintheshader,eachcubecanhaveadifferentposition,rotationspeedandcolour.Thistechniquecanbeusedwhereverrepeatedgeometryisusedinascene. GeneratingaGeometry Torenderacube(whichisthemostbasic3Dshape)weneedtogeneratecoordinatesforitsvertices.Thisisthefirststepwewouldliketofocuson.Pleaselookattheimagebelow. Coordinatesofcubevertices. Asshownintheimage,thecubevertexcoordinatesarearrangedaroundpoint<0,0,0>whichplacesthemin[,<1,1,1>]range.Thisisnotnecessary.Youareabletotranslatethecoordinatesinanydirectionortoscalethecube,butyouhavetobesurethatyourcubewillbestillvisibleonthescreen.Ifyouarenotsurehowtodothat,justfollowoursuggestions.Thereisanotherreasonforustousethecoordinatesarrangedaroundthecenterofthescreen(point<0,0,0>)-wewillthengeneratecopiesofthecubeandeachinstancewillbetranslatedtoanewposition(sothatthecubesmoveonacirculartrajectory).Butmoreaboutthislater. Tohavecubeverticesisnotenoughtodrawthecubicshape.ThebasicOpenGLESrenderingtechniqueisbasedondrawingtrianglesthatmakeuparequestedshape.Thiswillbeournextstep.Thisisimportanttomentionherethatwhilstdescribingcubetrianglevertices,youshouldfollowtheclockwiseorcounter-clockwiseorder,otherwiseOpenGLESwillhavesometroublewithdetectingfrontandbackfaces.Inthisexampleweareusingclockwise(CW)ordertodescribecubecoordinatesasthisisthedefaultforOpenGLES. Triangleswhichmakeupacubicshape. Pleaselookatthecodepresentedbelowformoredetails. /*Pleaseseeheaderforthespecification.*/ voidCubeModel::getTriangleRepresentation(float**coordinatesPtrPtr, int*numberOfCoordinatesPtr, int*numberOfPointsPtr, floatscalingFactor) { ASSERT(coordinatesPtrPtr!=NULL, "Cannotusenullpointerwhilecalculatingcoordinates"); /*Indexofanarraywewillputnewpointcoordinatesat.*/ intcurrentIndex=0; /*6facesofcube,2trianglesforeachface,3pointsoftriangle,3coordinatesforeachpoint.*/ constintnumberOfCubeTriangleCoordinates=NUMBER_OF_CUBE_FACES* NUMBER_OF_TRIANGLES_IN_QUAD* NUMBER_OF_TRIANGLE_VERTICES* NUMBER_OF_POINT_COORDINATES; /*Allocatememoryforresultarray.*/ *coordinatesPtrPtr=(float*)malloc(numberOfCubeTriangleCoordinates*sizeof(float)); /*Isallocationsuccessful?.*/ ASSERT(*coordinatesPtrPtr!=NULL, "Couldnotallocatememoryforresultarray.") /*Example: *Coordinatesforcubepoints: *A-1.0f,1.0f,1.0f *B-1.0f,1.0f,-1.0f *C1.0f,1.0f,-1.0f *D1.0f,1.0f,1.0f *E-1.0f,-1.0f,1.0f *F-1.0f,-1.0f,-1.0f *G1.0f,-1.0f,-1.0f *H1.0f,-1.0f,1.0f *Create2trianglesforeachfaceofthecube.Verticesarewritteninclockwiseorder. *B________C */|/| *A.........D| *.|.| *.F|__.___|G *././ *E.........H */ constVec3fpointA={-1.0f,1.0f,1.0f}; constVec3fpointB={-1.0f,1.0f,-1.0f}; constVec3fpointC={1.0f,1.0f,-1.0f}; constVec3fpointD={1.0f,1.0f,1.0f}; constVec3fpointE={-1.0f,-1.0f,1.0f}; constVec3fpointF={-1.0f,-1.0f,-1.0f}; constVec3fpointG={1.0f,-1.0f,-1.0f}; constVec3fpointH={1.0f,-1.0f,1.0f}; /*Fillthearraywithcoordinates.*/ /*Topface.*/ /*A*/ (*coordinatesPtrPtr)[currentIndex++]=pointA.x; (*coordinatesPtrPtr)[currentIndex++]=pointA.y; (*coordinatesPtrPtr)[currentIndex++]=pointA.z; /*B*/ (*coordinatesPtrPtr)[currentIndex++]=pointB.x; (*coordinatesPtrPtr)[currentIndex++]=pointB.y; (*coordinatesPtrPtr)[currentIndex++]=pointB.z; /*C*/ (*coordinatesPtrPtr)[currentIndex++]=pointC.x; (*coordinatesPtrPtr)[currentIndex++]=pointC.y; (*coordinatesPtrPtr)[currentIndex++]=pointC.z; /*A*/ (*coordinatesPtrPtr)[currentIndex++]=pointA.x; (*coordinatesPtrPtr)[currentIndex++]=pointA.y; (*coordinatesPtrPtr)[currentIndex++]=pointA.z; /*C*/ (*coordinatesPtrPtr)[currentIndex++]=pointC.x; (*coordinatesPtrPtr)[currentIndex++]=pointC.y; (*coordinatesPtrPtr)[currentIndex++]=pointC.z; /*D*/ (*coordinatesPtrPtr)[currentIndex++]=pointD.x; (*coordinatesPtrPtr)[currentIndex++]=pointD.y; (*coordinatesPtrPtr)[currentIndex++]=pointD.z; /*Bottomface.*/ /*F*/ (*coordinatesPtrPtr)[currentIndex++]=pointF.x;; (*coordinatesPtrPtr)[currentIndex++]=pointF.y;; (*coordinatesPtrPtr)[currentIndex++]=pointF.z;; /*E*/ (*coordinatesPtrPtr)[currentIndex++]=pointE.x; (*coordinatesPtrPtr)[currentIndex++]=pointE.y; (*coordinatesPtrPtr)[currentIndex++]=pointE.z; /*H*/ (*coordinatesPtrPtr)[currentIndex++]=pointH.x; (*coordinatesPtrPtr)[currentIndex++]=pointH.y; (*coordinatesPtrPtr)[currentIndex++]=pointH.z; /*F*/ (*coordinatesPtrPtr)[currentIndex++]=pointF.x; (*coordinatesPtrPtr)[currentIndex++]=pointF.y; (*coordinatesPtrPtr)[currentIndex++]=pointF.z; /*H*/ (*coordinatesPtrPtr)[currentIndex++]=pointH.x; (*coordinatesPtrPtr)[currentIndex++]=pointH.y; (*coordinatesPtrPtr)[currentIndex++]=pointH.z; /*G*/ (*coordinatesPtrPtr)[currentIndex++]=pointG.x; (*coordinatesPtrPtr)[currentIndex++]=pointG.y; (*coordinatesPtrPtr)[currentIndex++]=pointG.z; /*Backface.*/ /*G*/ (*coordinatesPtrPtr)[currentIndex++]=pointG.x; (*coordinatesPtrPtr)[currentIndex++]=pointG.y; (*coordinatesPtrPtr)[currentIndex++]=pointG.z; /*C*/ (*coordinatesPtrPtr)[currentIndex++]=pointC.x; (*coordinatesPtrPtr)[currentIndex++]=pointC.y; (*coordinatesPtrPtr)[currentIndex++]=pointC.z; /*B*/ (*coordinatesPtrPtr)[currentIndex++]=pointB.x; (*coordinatesPtrPtr)[currentIndex++]=pointB.y; (*coordinatesPtrPtr)[currentIndex++]=pointB.z; /*G*/ (*coordinatesPtrPtr)[currentIndex++]=pointG.x; (*coordinatesPtrPtr)[currentIndex++]=pointG.y; (*coordinatesPtrPtr)[currentIndex++]=pointG.z; /*B*/ (*coordinatesPtrPtr)[currentIndex++]=pointB.x; (*coordinatesPtrPtr)[currentIndex++]=pointB.y; (*coordinatesPtrPtr)[currentIndex++]=pointB.z; /*F*/ (*coordinatesPtrPtr)[currentIndex++]=pointF.x; (*coordinatesPtrPtr)[currentIndex++]=pointF.y; (*coordinatesPtrPtr)[currentIndex++]=pointF.z; /*Frontface.*/ /*E*/ (*coordinatesPtrPtr)[currentIndex++]=pointE.x; (*coordinatesPtrPtr)[currentIndex++]=pointE.y; (*coordinatesPtrPtr)[currentIndex++]=pointE.z; /*A*/ (*coordinatesPtrPtr)[currentIndex++]=pointA.x; (*coordinatesPtrPtr)[currentIndex++]=pointA.y; (*coordinatesPtrPtr)[currentIndex++]=pointA.z; /*D*/ (*coordinatesPtrPtr)[currentIndex++]=pointD.x; (*coordinatesPtrPtr)[currentIndex++]=pointD.y; (*coordinatesPtrPtr)[currentIndex++]=pointD.z; /*E*/ (*coordinatesPtrPtr)[currentIndex++]=pointE.x; (*coordinatesPtrPtr)[currentIndex++]=pointE.y; (*coordinatesPtrPtr)[currentIndex++]=pointE.z; /*D*/ (*coordinatesPtrPtr)[currentIndex++]=pointD.x; (*coordinatesPtrPtr)[currentIndex++]=pointD.y; (*coordinatesPtrPtr)[currentIndex++]=pointD.z; /*H*/ (*coordinatesPtrPtr)[currentIndex++]=pointH.x; (*coordinatesPtrPtr)[currentIndex++]=pointH.y; (*coordinatesPtrPtr)[currentIndex++]=pointH.z; /*Rightface.*/ /*H*/ (*coordinatesPtrPtr)[currentIndex++]=pointH.x; (*coordinatesPtrPtr)[currentIndex++]=pointH.y; (*coordinatesPtrPtr)[currentIndex++]=pointH.z; /*D*/ (*coordinatesPtrPtr)[currentIndex++]=pointD.x; (*coordinatesPtrPtr)[currentIndex++]=pointD.y; (*coordinatesPtrPtr)[currentIndex++]=pointD.z; /*C*/ (*coordinatesPtrPtr)[currentIndex++]=pointC.x; (*coordinatesPtrPtr)[currentIndex++]=pointC.y; (*coordinatesPtrPtr)[currentIndex++]=pointC.z; /*H*/ (*coordinatesPtrPtr)[currentIndex++]=pointH.x; (*coordinatesPtrPtr)[currentIndex++]=pointH.y; (*coordinatesPtrPtr)[currentIndex++]=pointH.z; /*C*/ (*coordinatesPtrPtr)[currentIndex++]=pointC.x; (*coordinatesPtrPtr)[currentIndex++]=pointC.y; (*coordinatesPtrPtr)[currentIndex++]=pointC.z; /*G*/ (*coordinatesPtrPtr)[currentIndex++]=pointG.x; (*coordinatesPtrPtr)[currentIndex++]=pointG.y; (*coordinatesPtrPtr)[currentIndex++]=pointG.z; /*Leftface.*/ /*F*/ (*coordinatesPtrPtr)[currentIndex++]=pointF.x; (*coordinatesPtrPtr)[currentIndex++]=pointF.y; (*coordinatesPtrPtr)[currentIndex++]=pointF.z; /*B*/ (*coordinatesPtrPtr)[currentIndex++]=pointB.x; (*coordinatesPtrPtr)[currentIndex++]=pointB.y; (*coordinatesPtrPtr)[currentIndex++]=pointB.z; /*A*/ (*coordinatesPtrPtr)[currentIndex++]=pointA.x; (*coordinatesPtrPtr)[currentIndex++]=pointA.y; (*coordinatesPtrPtr)[currentIndex++]=pointA.z; /*F*/ (*coordinatesPtrPtr)[currentIndex++]=pointF.x; (*coordinatesPtrPtr)[currentIndex++]=pointF.y; (*coordinatesPtrPtr)[currentIndex++]=pointF.z; /*A*/ (*coordinatesPtrPtr)[currentIndex++]=pointA.x; (*coordinatesPtrPtr)[currentIndex++]=pointA.y; (*coordinatesPtrPtr)[currentIndex++]=pointA.z; /*E*/ (*coordinatesPtrPtr)[currentIndex++]=pointE.x; (*coordinatesPtrPtr)[currentIndex++]=pointE.y; (*coordinatesPtrPtr)[currentIndex++]=pointE.z; /*Calculatesizeofacube.*/ if(scalingFactor!=1.0f) { for(inti=0;i