RenderingPipeline（渲染管線）DongfengLiuSchoolofInformationEngineeringGuangdongUniversityofTechnologyGuangzhou,ChinaOutline

計算機圖形技術(shù)：3Dworldto2Dimage;三個步驟：變換（transform），模型變換、視點變換和投影變換裁剪，剔除位于裁剪面之外的物體視口變換，上述變換后的坐標與屏幕像素之間建立對應(yīng)關(guān)系。

geometricalinformation—圖元RenderingPipelineCoordinatesystemsinUnity

ZYX1.坐標系統(tǒng)對象坐標系(objectcoordinatesystem:OCS)x,y,z世界坐標系(worldcoordinatesystem:WCS)X,Y,Z相機坐標系(viewingcoordinatesystem:VCS)n,u,v（n的方向是從視點指向center的方向）投影坐標系(clippingcoordinatesystem:CCS)X,Y,Z(規(guī)格化設(shè)備坐標系，坐標值-1~1之間)窗口坐標系(devicecoordinatesystem:DCS)x,y,z(z:0~1,x,y以窗口左下角為坐標原點)2.模型視點變換場景從世界坐標系到相機坐標系的變換。2.1模型變換在WCS中改變物體的位置、姿態(tài)、或縮放2.2視點變換調(diào)整相機位置和方向，對場景進行取景3.投影變換場景從相機坐標系到投影坐標系的變換。通過投影矩陣Mprojection來實現(xiàn)：4.視口變換場景從投影坐標系到窗口坐標系的變換。通過投影矩陣Mwindow來實現(xiàn)：ModelTransformOCSMTWCSViewTransformWCSVT（Camera）VCSProjectionTransformVCSPTCCSViewFrustum(視景體)近剪切面遠剪切面透視投影，正交投影ViewportTransformCCSVTDCSSomeConcepts

the“camera”you’vecreatedinyour3Dpackageisn’treallyacameraatall.Itjustrepresentsaviewtransformation.Cameraincomputergraphics,wedothisbydefiningwhat’scalleda“viewfrustum”.

Withaviewfrustum,anythinginsidethevolumeofthefrustumisdrawn.Everythingoutsideisexcludedor“clipped”.Projection

Getridofanythingthatisnotintheviewfrustum.ClippingAlloftheoperationsthatwe’vedoneabovearestillin3D(X,Y,Z)coordinates.Weneedtomapthesecoordinatestotheviewportdimensions.Forexample,wemightberunningagameat1920×1080,sowehavetoconvertallthegeometriccoordinatesintopixelcoordinates.深度bufferScreenMapping（屏幕映射）Rasterization

Arasterdisplay,isbasicallyagridofpixels.Eachpixelhascolorvaluesassigned.A“framebuffer”storesthedataforeachpixel.Todeterminethestateofeachpixelinascreen:Ateachpixel,whatshouldbevisible.Whatcolorthepixelshouldbe.計算機顏色RGBA(red,green,blue,alpha)(0.3,0.5,0.2,1)forexa