计算机图形学computergraph课件

PPTglMatrixMode(GL_PROJECTION);,33,CurrentTransformationMatrix(CTM),Conceptuallythereisa4x4homogeneouscoordinatematrix,thecurrenttransformationmatrix(CTM)thatispartofthestateandisappliedtoallverticesthatpassdownthepipelineTheCTMisdefinedintheuserprogramandloadedintoatransformationunit,CTM,vertices,vertices,p,p=Cp,C,34,CTMoperations,TheCTMcanbealteredeitherbyloadinganewCTMorbypostmutiplication,Loadanidentitymatrix:CILoadanarbitrarymatrix:CMLoadatranslationmatrix:CTLoadarotationmatrix:CRLoadascalingmatrix:CSPostmultiplybyanarbitrarymatrix:CCMPostmultiplybyatranslationmatrix:CCTPostmultiplybyarotationmatrix:CCRPostmultiplybyascalingmatrix:CCS,35,RotationaboutaFixedPoint,Startwithidentitymatrix:CIMovefixedpointtoorigin:CCTRotate:CCRMovefixedpointback:CCT-1Result:C=TRT1whichisbackwards.Thisresultisaconsequenceofdoingpostmultiplications.Letstryagain.,36,ReversingtheOrder,WewantC=T1RTsowemustdotheoperationsinthefollowingorderCICCT-1CCRCCTEachoperationcorrespondstoonefunctioncallintheprogram.Notethatthelastoperationspecifiedisthefirstexecutedintheprogram,37,CTMinOpenGL,OpenGLhasamodel-viewandaprojectionmatrixinthepipelinewhichareconcatenatedtogethertoformtheCTMCanmanipulateeachbyfirstsettingthecorrectmatrixmode,38,Rotation,Translation,Scaling,glRotatef(theta,vx,vy,vz),glTranslatef(dx,dy,dz),glScalef(sx,sy,sz),glLoadIdentity(),Loadanidentitymatrix:,Multiplyonright:,thetaindegrees,(vx,vy,vz)defineaxisofrotation,Eachhasafloat(f)anddouble(d)format(glScaled),39,Example,Rotationaboutzaxisby30degreeswithafixedpointof(1.0,2.0,3.0)RememberthatlastmatrixspecifiedintheprogramisthefirstappliedDemo,glMatrixMode(GL_MODELVIEW);glLoadIdentity();glTranslatef(1.0,2.0,3.0);glRotatef(30.0,0.0,0.0,1.0);glTranslatef(-1.0,-2.0,-3.0);,40,ArbitraryMatrices,CanloadandmultiplybymatricesdefinedintheapplicationprogramThematrixmisaonedimensionarrayof16elementswhicharethecomponentsofthedesired4x4matrixstoredbycolumnsInglMultMatrixf,mmultipliestheexistingmatrixontheright,glLoadMatrixf(m)glMultMatrixf(m),Matrixmultiply,/沿Y轴向上平移10个单位glTranslatef(0,10,0);/画第一个球体DrawSphere(5);/沿X轴向左平移10个单位glTranslatef(10,0,0);/画第二个球体DrawSphere(5);,41,procedureRenderScene();beginglMatrixMode(GL_MODELVIEW);/沿Y轴向上平移10个单位glTranslatef(0,10,0);/画第一个球体DrawSphere(5);/加载单位矩阵glLoadIdentity();/沿X轴向上平移10个单位glTranslatef(10,0,0);/画第二个球体DrawSphere(5);end;,42,MatrixStacks,InmanysituationswewanttosavetransformationmatricesforuselaterTraversinghierarchicaldatastructuresAvoidingstatechangeswhenexecutingdisplaylistsOpenGLmaintainsstacksforeachtypeofmatrixAccesspresenttype(assetbyglMatrixMode)by,glPushMatrix()glPopMatrix(),GL_PROJECTION,GL_MODEVIEW,MatrixStacks,procedureRenderScene();beginglMatrixMode(GL_MODELVIEW);/pushmatrixstackglPushMatrix;/translate10alongYaxisglTranslatef(0,10,0);/drawthefirstsphereDrawSphere(5);/comebacktothelastsavedstateglPopMatrix;/translate10alongXaxisglTranslatef(10,0,0);/drawthesecondsphereDrawSphere(5);end;,43,44,ReadingBackMatrices,Canalsoaccessmatrices(andotherpartsofthestate)byqueryfunctionsFormatrices,weuseas,glGetIntegervglGetFloatvglGetBooleanvglGetDoublevglIsEnabled,floatm16;glGetFloatv(GL_MODELVIEW,m);,45,UsingTransformations,Example:useidlefunctiontorotateacubeandmousefunctiontochangedirectionofrotationStartwithaprogramthatdrawsacube(colorcube.c)inastandardwayCenteredatoriginSidesalignedwithaxesWilldiscussmodelinginnextlecture,46,main.c,voidmain(intargc,char*argv)glutInit(,47,IdleandMousecallbacks,voidspinCube()thetaaxis+=2.0;if(thetaaxis360.0)thetaaxis-=360.0;glutPostRedisplay();,voidmouse(intbtn,intstate,intx,inty)char*sAxis=X-axis,Y-axis,Z-axis;/*mousecallback,selectsanaxisaboutwhichtorotate*/if(btn=GLUT_LEFT_BUTTON,48,Displaycallback,voiddisplay()glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);glLoadIdentity();glRotatef(theta0,1.0,0.0,0.0);glRotatef(theta1,0.0,1.0,0.0);glRotatef(theta2,0.0,0.0,1.0);colorcube();glutSwapBuffers();,Notethatbecauseoffixedfromofcallbacks,variablessuchasthetaandaxismustbedefinedasglobalsDemo,PolygonalMesh,49,Polygonalmesh,50,Object,Pointcloud,Surfacereconstruction,Polygonalmesh,PhDthesisofHuguesHoppe1994,Meshsmoothing,Polygonalmesh,Non-iterative,featurepreservingmeshsmoothingACMTransactionsonGraphics,2003,Meshsimplification,Polygonalmesh,CGAL,manual,Parameterization,Polygonalmesh,Polygonalmesh,Meshmorphing,Polygonalmesh,MeanValueCoordinatesforC