【Unity】URP源码分析(管线篇)

RhinoFreak

（基于Unity 2021.3.8、URP 12.1.7）

管线 (Pipeline)

UniversalRenderPipelineAsset.cs

属性

• Rendering Settings
  
  
  
  • rendererDataList (渲染器数据列表)
    
  • defaultRendererIndex (默认开启的渲染器索引)
    
  • requireDepthTexture (是否生成_CameraDepthTexture, 在Shader中使用)
    
  • requireOpaqueTexture (是否生成_CameraOpaqueTexture, 在Shader中使用)
    
  • opaqueDownsampling (_CameraOpaqueTexture的降采样倍率)
    
  
  

• Quality Settings
  
  
  
  • supportsHDR (是否开启HDR)
    
  • MSAA (_2x、_4x、_8x) (开启2、4、8倍MSAA抗锯齿)
    
  • renderScale (cameraColorTarget、cameraDepthTarget的分辨率缩放)
    
  
  

• Lighting Settings
  
  
  
  • mainLightRenderingMode (PerVertex、PerPixel)
    
  • mainLightShadowsSupported (是否开启主光源阴影)
    
  • mainLightShadowmapResolution (主光源阴影贴图分辨率)
    
  • additionalLightsRenderingMode (PerVertex、PerPixel)
    
  • additionalLightsPerObjectLimit (每个物体接收的最大额外光源数量)
    
  • additionalLightShadowsSupported (是否开启额外光源阴影)
    
  • additionalLightsShadowmapResolution (额外光源阴影贴图分辨率)
    
  • Reflection Probes Settings
    
    
    
    • reflectionProbeBlending (是否开启多个反射探针混合)
      
    • reflectionProbeBoxProjection (是否开启盒体投影)
      
    
    
  • supportsLightLayers (是否开启光照图层)
    
  
  

• Shadows Settings
  
  
  
  • shadowDistance (多少距离内生成阴影)
    
  • shadowCascadeCount (CSM层数)
    
  • cascade2Split、cascade3Split、cascade4Split (第一二层、二三层、三四层的划分距离)
    
  • shadowDepthBias (阴影深度偏移值)
    
  • shadowNormalBias (阴影法线偏移值)
    
  • softShadowsSupported (是否开启软阴影)
    
  
  

• Post Processing Settings
  
  
  
  • colorGradingMode (LDR、HDR)
    
  
  

• Advanced Settings
  
  
  
  • useSRPBatcher (是否开启SRP合批)
    
  • supportsDynamicBatching (是否开启动态合批)
    
  
  

方法

• Create (创建UniversalRenderPipelineAsset、UniversalRendererData实例)
  

UniversalRenderPipeline.cs

属性

• maxPerObjectLights (每个物体接收的最大光源数量)
  
• maxVisibleAdditionalLights (最大可见的额外光源数量, 传入到Shader中的额外光源的信息数组)
  
• globalSettings (渲染管线全局设置)
  

方法

• Render
  
  
  
  • BeginContextRendering ->
    
  • BeginFrameRendering ->
    
  • SetupPerFrameShaderConstants (_GlossyEnvironmentColor、_GlossyEnvironmentCubeMap) ->
    
  • SortCameras ->
    
  • For Loop Cameras ->
    
    
    
    • BeginCameraRendering
      
    • UpdateVolumeFramework (更新Volume后处理参数)
      
    • InitializeCameraData (初始化CameraData结构体、CreateRenderTextureDescriptor)
      
    • RenderSingleCamera
      
      
      
      • TryGetCullingParameters
        
      • renderer.OnPreCullRenderPasses (For Loop rendererFeatures.OnCameraPreCull)
        
      • context.Cull
        
      • InitializeRenderingData (GetMainLightIndex、cullResults、cameraData、lightData、shadowData、postProcessingData、perObjectData)
        
      • renderer.Setup
        
      • renderer.Execute
        
      
      
    • EndCameraRendering
      
    
    
  • EndFrameRendering ->
    
  • EndContextRendering
    
  
  

UniversalRenderPipelineCore.cs

属性

• asset (URP管线资产)
  

定义

• RenderingData (CullingResults、CameraData、LightData、ShadowData、PostProcessingData、PerObjectData)
  
• ShaderPropertyId (全局Shader属性的ID)
  
• ShaderKeywordStrings (全局Shader关键字)
  

UniversalRenderPipelineGlobalSettings.cs

属性

• lightLayerNames (光照图层的名称)
  
• stripDebugVariants (剔除调试用的变体)
  
• stripUnusedPostProcessingVariants (剔除不用到的后处理变体)
  
• stripUnusedVariants (剔除不用到的变体)
  

<hr/><hr/>渲染器 (Renderer)

ScriptableRenderer.cs

属性

• cameraColorTarget (相机渲染的颜色目标)
  
• cameraDepthTarget (相机渲染的深度目标)
  
• rendererFeatures (渲染特性列表)
  
• activeRenderPassQueue (渲染Pass队列)
  

方法

• ScriptableRenderer构造函数 (For Loop rendererFeatures.Create)
  
• Setup (抽象函数)
  
• Execute
  
  
  
  • InternalStartRendering (For Loop activeRenderPassQueue.OnCameraSetup) ->
    
  • SetShaderTimeValues (_Time、_SinTime、_CosTime、unity_DeltaTime) ->
    
  • SortStable (Sort Render Pass) ->
    
  • SetupLights (虚函数) ->
    
  • SetPerCameraShaderVariables (_ProjectionParams、_WorldSpaceCameraPos、_ScreenParams、_ScaledScreenParams、_ZBufferParams、unity_OrthoParams、_GlobalMipBias) ->
    
    
    
    • SetCameraMatrices (worldToCameraMatrix、cameraToWorldMatrix、inverseViewMatrix、inverseProjectionMatrix、inverseViewAndProjectionMatrix) ->
      
    
    
  • ExecuteBlock (BeforeRendering、MainRenderingOpaque、MainRenderingTransparent、AfterRendering) ->
    
    
    
    • ExecuteRenderPass (执行每个Block的渲染Pass)
      
      
      
      • renderPass.Configure
        
      • SetRenderPassAttachments
        
        
        
        • SetRenderTarget (设置RenderPass中所指定的ColorAttachment、DepthAttachment)
          
        
        
      • renderPass.Execute
        
      
      
    
    
  • InternalFinishRendering (For Loop activeRenderPassQueue.OnCameraCleanup、activeRenderPassQueue.OnFinishCameraStackRendering)
    
  
  
• AddRenderPasses (For Loop rendererFeatures.AddRenderPasses)
  

UniversalRenderer.cs

属性

• renderingMode (渲染模式, Forward、Deferred)
  
• depthPrimingMode (是否开启Depth Prepass)
  
• forwardLights (前向渲染光源的处理封装)
  
• deferredLights (延迟渲染光源的处理封装)
  

方法

• UniversalRenderer构造函数 (初始化渲染Pass、_CameraColorAttachment、_CameraDepthAttachment、_CameraDepthTexture、_CameraNormalsTexture、_CameraOpaqueTexture)
  
• Setup
  
  
  
  • forwardLights.ProcessLights (只对Cluster Rendering生效)
    
  • AddRenderPasses (调用ScriptableRenderer.cs中的)
    
  • EnqueuePass (渲染Pass添加到渲染队列)
    
  • CreateCameraRenderTarget (只对Base Camera生效)
    
  • ConfigureCameraTarget
    
  
  
• SetupLights (forwardLights.Setup、deferredLights.SetupLights)
  

ForwardLights.cs

方法

• Setup (_ADDITIONAL_LIGHTS_VERTEX、_ADDITIONAL_LIGHTS、_CLUSTERED_RENDERING、LIGHTMAP_SHADOW_MIXING、SHADOWS_SHADOWMASK、_MIXED_LIGHTING_SUBTRACTIVE、_REFLECTION_PROBE_BLENDING、_REFLECTION_PROBE_BOX_PROJECTION、_LIGHT_LAYERS)
  
  
  
  • SetupShaderLightConstants (设置光源常量属性)
    
    
    
    • SetupMainLightConstants (_MainLightPosition、_MainLightColor、_MainLightOcclusionProbes、_MainLightLayerMask)
      
    • SetupAdditionalLightConstants (_AdditionalLightsPosition、_AdditionalLightsColor、_AdditionalLightsAttenuation、_AdditionalLightsSpotDir、_AdditionalLightsOcclusionProbes、_AdditionalLightsLayerMasks、_AdditionalLightsCount)
      
      
      
      • SetupPerObjectLightIndices (去除主光源, 设置物体的额外光源索引)
        
      
      
    
    
  
  

DeferredLights.cs

属性

• GbufferAttachments (MRT输出的Gbuffer信息)
  

方法

• SetupLights
  
  
  
  • PrecomputeTiles (只对TiledDeferredShading生效, 根据裁剪平面FrustumPlanes生成Tiles)
    
  • PrecomputeLights (Precompute Punctual Light Data)
    
  • SetupShaderLightConstants (设置光源常量属性)
    
    
    
    • SetupMainLightConstants (_MainLightPosition、_MainLightColor、_MainLightLayerMask)
      
    
    
  • SortLights (只对TiledDeferredShading生效)
    
  • CullFinalLights (只对TiledDeferredShading生效)
    
  
  
• Setup (初始化GbufferAttachments、DepthAttachment)
  
• ExecuteDeferredPass
  
  
  
  • SetupMatrixConstants (_ScreenToWorld)
    
  • RenderStencilLights
    
    
    
    • RenderStencilDirectionalLights (FullscreenMesh)
      
    • RenderStencilPointLights (SphereMesh)
      
    • RenderStencilSpotLights (HemisphereMesh)
      
    
    
  • RenderTileLights (只对TiledDeferredShading生效)
    
  • RenderFog
    
  
  

ScriptableRendererData.cs

属性

• rendererFeatures (渲染特性列表)
  

UniversalRendererData.cs

属性

• shaders (内置Shader/Utils目录下的着色器资源)
  
• opaqueLayerMask、transparentLayerMask (不透明、半透明物体的层遮罩)
  
• defaultStencilState (默认模板测试状态)
  
• renderingMode (渲染模式, Forward、Deferred)
  
• depthPrimingMode (是否开启Depth Prepass)
  

<hr/><hr/>渲染特性 (Renderer Feature)

ScriptableRendererFeature.cs

• Create (抽象函数)
  
• OnCameraPreCull (虚函数)
  
• AddRenderPasses (抽象函数)
  
• Dispose (虚函数)
  

RenderObjects.cs

• RenderObjectsPass
  
  
  
  • SetDetphState (设置深度缓冲区状态)
    
  • SetStencilState (设置模板测试状态)
    
  
  
• RenderObjectsSettings
  
  
  
  • renderPassEvent (渲染Pass的执行时机事件)
    
  • overrideMaterial (覆盖的材质)
    
  • overrideMaterialPassIndex (覆盖材质的Pass索引)
    
  • depthCompareFunction (深度比较方式)
    
  • enableWrite (深度是否写入)
    
  • filterSettings
    
    
    
    • renderQueueType (渲染队列)
      
    • layerMask (层遮罩)
      
    • passNames (光照模式LightMode)
      
    
    
  • stencilSettings
    
    
    
    • stencilReference (模板引用值)
      
    • stencilCompareFunction (模板比较方式)
      
    • passOperation (模板值通过后的操作)
      
    • failOperation (模板值失败后的操作)
      
    • zFailOperation (深度比较失败后的操作)
      
    
    
  • cameraSettings
    
    
    
    • offset (相机位置偏移)
      
    • cameraFieldOfView (视野FOV)
      
    
    
  
  

DecalRendererFeature.cs

• DecalGBufferRenderPass (执行Shader中LightMode为DecalGBufferMesh的Pass, 从GBuffer深度重建世界坐标, Shader实现可参考ShaderPassDecal.hlsl)
  
• DBufferRenderPass (执行Shader中LightMode为DBufferMesh的Pass, 将贴花固有色, 法线, 金属度、光滑度、AO、自发光渲染到DBuffer的_DBUFFER_MRT1、_DBUFFER_MRT2、_DBUFFER_MRT3, 正常渲染时采样_DBufferTexture使用DBuffer数据覆盖SurfaceData, Shader实现可参考ShaderPassDecal.hlsl、DBuffer.hlsl)
  
• DecalScreenSpaceRenderPass (执行Shader中LightMode为DecalScreenSpaceMesh的Pass, 从深度重建世界坐标、法线, Shader实现可参考ShaderPassDecal.hlsl)
  

ScreenSpaceAmbientOcclusion.cs

• ScreenSpaceAmbientOcclusionPass (生成_ScreenSpaceOcclusionTexture, Shader实现可参考SSAO.hlsl)
  

ScreenSpaceShadows.cs

• ScreenSpaceShadowsPass (根据深度、_MainLightShadowmapTexture生成_ScreenSpaceShadowmapTexture, 设置关键字_MAIN_LIGHT_SHADOWS_SCREEN)
  

<hr/><hr/>
渲染目标 (Render Target)

RenderTargetHandle.cs

• int类型id、RenderTargetIdentifier类型rtid的封装, Init时调用Shader.PropertyToID绑定id
  

RenderTargetBufferSystem.cs

• frontBuffer和backBuffer双缓冲的封装