【Unity】URP源码分析(Shader篇)

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（基于Unity 2021.3.8、URP 12.1.7）

着色器 (Shader)

光照模式 (LightMode)

• UniversalForward (前向 Pass)
  
• ShadowCaster (阴影 Pass)
  
• DepthOnly (深度 Pass)
  
• DepthNormals (深度+法线 Pass)
  
• Meta (烘焙 Pass)
  
• UniversalGBuffer (GBuffer Pass)
  

<hr/>输入 (Input)

UnityInput.hlsl

• _Time、_SinTime、_CosTime、unity_DeltaTime (时间相关)
  
• _WorldSpaceCameraPos、_ProjectionParams、_ScreenParams、_GlobalMipBias、_ZBufferParams、unity_OrthoParams (相机参数相关)
  
• unity_RenderingLayer (渲染层)
  
• unity_LightData、unity_LightIndices(光源数据相关, 光源总数、光源偏移量、光源索引)
  
• unity_SpecCube0、unity_SpecCube1 (反射探针相关)
  
• unity_Lightmap、unity_LightmapST (光照贴图缩放、偏移量)
  
• unity_ShadowMask (阴影遮罩相关)
  
• unity_SHAr、unity_SHAg、unity_SHAb、unity_SHBr、unity_SHBg、unity_SHBb、unity_SHC (球谐系数)
  

Input.hlsl

• InputData (输入数据结构体, positionWS、positionCS、normalWS、viewDirectionWS、shadowCoord、fogCoord、vertexLighting、bakedGI、normalizedScreenSpaceUV、shadowMask、tangentToWorld)
  
• _GlossyEnvironmentColor、_GlossyEnvironmentCubeMap (环境光、间接高光)
  
• _MainLightPosition、_MainLightColor、_MainLightOcclusionProbes、_MainLightLayerMask、_AdditionalLightsCount、_AdditionalLightsPosition、_AdditionalLightsColor、_AdditionalLightsAttenuation、_AdditionalLightsSpotDir、_AdditionalLightsOcclusionProbes、_AdditionalLightsLayerMasks (主光源、额外光源信息)
  
• UNITY_MATRIX_XXX (顶点变换矩阵)
  

SurfaceInput.hlsl

• _BaseMap、_BumpMap、_EmissionMap定义
  

<hr/>空间变换 (Space Transform)

SpaceTransforms.hlsl

• 顶点位置P、向量Dir的模型空间Model、视图空间View、裁剪空间Projection的矩阵变换, 法线Normal的矩阵变换, 切线Tangent的矩阵变换
  

<hr/>光照 (Lighting)

BRDF.hlsl

• BRDFData (BRDF数据结构体, albedo、diffuse、specular、reflectivity、roughness)
  
• InitializeBRDFData (初始化BRDF数据结构体)
  
• DirectBRDFSpecular (直接光镜面反射计算)
  

Lighting.hlsl

• DECLARE_LIGHTMAP_OR_SH (LIGHTMAP_ON开启则定义lightmapUV, 否则定义vertexSH)
  
• OUTPUT_LIGHTMAP_UV (根据input.lightmapUV、unity_LightmapST输出到output.lightmapUV)
  
• OUTPUT_SH (根据normalWS、SampleSHVertex输出到output.vertexSH)
  
• LightingData (光照数据结构体, giColor、mainLightColor、additionalLightsColor、vertexLightingColor、emissionColor)
  
• VertexLighting (额外光逐顶点光照)
  
• UniversalFragmentPBR (PBR光照计算)
  
  
  
  • MixRealtimeAndBakedGI (从LightMap中减去主光的贡献, 只对_MIXED_LIGHTING_SUBTRACTIVE烘焙模式生效)
    
  • GlobalIllumination (GI计算)
    
  • LightingPhysicallyBased (PBR漫反射+镜面反射)
    
  
  
• UniversalFragmentBlinnPhong (BlinnPhong光照计算)
  
  
  
  • LightingLambert (BlinnPhong漫反射)
    
  • LightingSpecular (BlinnPhong镜面反射)
    
  
  

RealtimeLights.hlsl

• Light (光源数据结构体, direction、color、distanceAttenuation、shadowAttenuation、layerMask)
  
• GetMeshRenderingLightLayer (获取网格渲染的光照图层LightLayer)
  
• DistanceAttenuation、AngleAttenuation (光源距离衰减、角度衰减)
  
• GetMainLight (根据_MainLightXXX, 获取主光源)
  
  
  
  • MainLightShadow (计算主光源阴影)
    
    
    
    • MainLightRealtimeShadow (_MAIN_LIGHT_SHADOWS_SCREEN开启采样_ScreenSpaceShadowmapTexture, 否则采样_MainLightShadowmapTexture)
      
    
    
  
  
• GetAdditionalLight (根据_AdditionalLightsXXX数组, 获取额外光源)
  
  
  
  • GetPerObjectLightIndex (获取额外光源索引)
    
  • GetAdditionalPerObjectLight (根据索引获取额外光源)
    
  • AdditionalLightShadow (计算额外光源阴影)
    
  
  
• CalculateShadowMask (计算阴影遮罩)
  

GlobalIllumination.hlsl

• SampleSHVertex (根据normalWS计算顶点球谐光)
  
  
  
  • SampleSH
    
  
  
• SampleSHPixel (根据normalWS、顶点球谐光计算像素球谐光)
  
  
  
  • SampleSH
    
  
  
• SAMPLE_GI (采样GI, LIGHTMAP_ON开启SampleLightmap、LIGHTMAP_ON关闭SampleSHPixel)
  
• GlossyEnvironmentReflection
  
  
  
  • CalculateIrradianceFromReflectionProbes (采样反射探针unity_SpecCube、环境立方贴图_GlossyEnvironmentCubeMap)
    
  
  
• GlobalIllumination
  
  
  
  • indirectDiffuse (bakeGI)
    
  • indirectSpecular (GlossyEnvironmentReflection)
    
  • EnvironmentBRDF (根据indirectDiffuse、diffuse计算PBR间接光漫反射)
    
    
    
    • EnvironmentBRDFSpecular (根据indirectSpecular、roughness、specular、fresnel计算PBR间接光镜面反射)
      
    
    
  
  
• MixRealtimeAndBakedGI
  
  
  
  • SubtractDirectMainLightFromLightmap (从LightMap中减去主光的贡献, 只对_MIXED_LIGHTING_SUBTRACTIVE烘焙模式生效)
    
  
  

MetaPass.hlsl

• UnityMetaInput (烘焙数据结构体, albedo、emission)
  
• UnityMetaFragment (输出固有色、自发光参与烘焙计算)
  

<hr/>阴影 (Shadow)

Shadows.hlsl

• _ScreenSpaceShadowmapTexture、_MainLightShadowmapTexture、_AdditionalLightsShadowmapTexture (屏幕空间阴影贴图、主光源阴影贴图、额外光源阴影贴图)
  
• TransformWorldToShadowCoord (根据positionWS、CSM对应索引的_MainLightWorldToShadow矩阵计算出阴影贴图的纹理坐标)
  
  
  
  • ComputeCascadeIndex (根据positionWS计算CSM对应索引值)
    
  
  
• MainLightShadow (计算主光源阴影)
  
  
  
  • MainLightRealtimeShadow (_MAIN_LIGHT_SHADOWS_SCREEN开启采样_ScreenSpaceShadowmapTexture, 否则采样_MainLightShadowmapTexture)
    
  
  
• AdditionalLightShadow (计算额外光源阴影)
  
  
  
  • AdditionalLightRealtimeShadow (采样_AdditionalLightsShadowmapTexture)
    
  
  

<hr/>其他 (Misc)

Macros.hlsl

• PI、INV_PI (圆周率、圆周率倒数)
  
• FLT_EPS、HALF_EPS (32位高精度浮点、16位半精度浮点的Epsilon值)
  
• TRANSFORM_TEX (纹理坐标缩放、偏移)
  

D3D11.hlsl、Vulkan.hlsl、Metal.hlsl

• UNITY_UV_STARTS_AT_TOP、UNITY_REVERSED_Z、UNITY_NEAR_CLIP_VALUE (1.0)、UNITY_RAW_FAR_CLIP_VALUE (0.0)
  
• VERTEXID_SEMANTIC (SV_VertexID)、INSTANCEID_SEMANTIC (SV_InstanceID)、FRONT_FACE_SEMANTIC (SV_IsFrontFace)、IS_FRONT_VFACE
  
• Flow Control Attributes
  
  
  
  • UNITY_BRANCH [branch] (动态分支, 逐个判断, 选择满足条件的一侧执行, 产生跳转指令)
    
  • UNITY_FLATTEN [flatten] (静态分支, 执行分支所有侧, 选择满足条件的一侧的结果, 不产生跳转指令)
    
  • UNITY_UNROLL [unroll] (循环展开)
    
  • UNITY_UNROLLX(_x) [unroll(_x)] (循环展开x次)
    
  • UNITY_LOOP [loop] (循环不展开)
    
  
  
• Texture & Sampler
  
  
  
  • TEXTURE2D、TEXTURE2D_ARRAY (2D纹理、2D纹理数组类型声明)
    
  • TEXTURECUBE、TEXTURECUBE_ARRAY (立方纹理、立方纹理数组类型声明)
    
  • TEXTURE3D (3D纹理类型声明)
    
  • RW_TEXTURE2D、RW_TEXTURE2D_ARRAY、RW_TEXTURE3D (可读写的2D、3D纹理类型声明, 用于Compute Shader)
    
  
  

GLES3.hlsl

• UNITY_NEAR_CLIP_VALUE (-1.0)、UNITY_RAW_FAR_CLIP_VALUE (1.0)
  
• VERTEXID_SEMANTIC (SV_VertexID)、INSTANCEID_SEMANTIC (SV_InstanceID)、FRONT_FACE_SEMANTIC (VFACE)、IS_FRONT_VFACE
  

Common.hlsl

• DegToRad、RadToDeg (角度转弧度、弧度转角度)
  
• Linear01Depth、LinearEyeDepth (深度贴图的非线性深度[0, 1]转为线性深度[0, 1]、非线性深度转为视图空间下的线性深度[near, far])
  
• Inverse (矩阵求逆)
  
• ComputeTextureLOD (根据uv、texelSize计算mipLevel)
  

ShaderVariablesFunctions.hlsl

• GetVertexPositionInputs (positionWS、positionVS、positionCS、positionNDC的计算)
  
• GetVertexNormalInputs (normalWS、tangentWS、bitangentWS的计算)
  
• GetCameraPositionWS (获取相机位置)
  
• GetWorldSpaceViewDir (相机位置V - 顶点位置P)
  
• ComputeFogFactor (根据positionCS.z值计算雾因子)
  
• MixFog (计算雾颜色)
  
  
  
  • ComputeFogIntensity (根据雾模式 (FOG_LINEAR、FOG_EXP、FOG_EXP2)、雾因子计算雾强度)
    
  
  
• LinearDepthToEyeDepth (从深度贴图的深度[0, 1]转为视空间深度[near, far])
  
• GetNormalizedScreenSpaceUV (根据positionCS转为屏幕空间uv)
  

NormalReconstruction.hlsl

• ReconstructNormalDerivative (根据positionCS、深度贴图的深度重建法线)
  
• ViewSpacePosAtPixelPosition (根据uv、深度贴图的深度转为视图空间下的Ray)
  

Color.hlsl

• SRGBToLinear、LinearToSRGB (sRGB与Linear的颜色空间转换)
  
• RgbToHsv、HsvToRgb、RotateHue (RGB与HSV的颜色空间转换、色环Hue值旋转)
  
• ApplyLut2D (Lut校色贴图采样)
  
• NeutralTonemap、AcesTonemap (NEUTRAL模式的Tonemapping、ACES模式的Tonemapping)
  
• EncodeRGBM、DecodeRGBM (RGBM编码、RGBM解码)
  

<hr/>延迟渲染 (Deferred Shading)

UnityGBuffer.hlsl

• FragmentOutput (GBuffer输出的SV_Target数据结构体)
  
• PackMaterialFlags、UnpackMaterialFlags (材质标记的编码/解码, uint转为float)
  
• PackNormal、UnpackNormal (法线的编码/解码, 正八面体映射)
  
• SurfaceDataToGbuffer、SurfaceDataFromGbuffer (SurfaceData数据与GBuffer数据的编码/解码)
  

R	G	B	A
Gbuffer0	albedo	albedo	albedo	materialFlags (sRGB rendertarget)
Gbuffer1	specular	specular	specular	occlusion
Gbuffer2	encoded-normal	encoded-normal	encoded-normal	smoothness
Gbuffer3	GI	GI	GI	[optional: see OutputAlpha()] (lighting buffer)

• BRDFDataToGbuffer、BRDFDataFromGbuffer (BRDFData数据与GBuffer数据的编码/解码)
  

R	G	B	A
Gbuffer0	diffuse	diffuse	diffuse	materialFlags (sRGB rendertarget)
Gbuffer1	metallic/specular	specular	specular	occlusion
Gbuffer2	encoded-normal	encoded-normal	encoded-normal	smoothness
Gbuffer3	GI	GI	GI	[optional: see OutputAlpha()] (lighting buffer)

StencilDeferred.shader

• Stencil Volume Pass (点光源、聚光源的像素遮挡剔除, 针对光源在几何体后面的情况)
  
• Deferred Punctual Light (Lit) Pass (点光源、聚光源的Lit光照计算)
  
• Deferred Punctual Light (SimpleLit) (点光源、聚光源的SimpleLit光照计算)
  
• Deferred Directional Light (Lit) (方向光源的Lit光照计算)
  
• Deferred Directional Light (SimpleLit) (方向光源的SimpleLit光照计算)
  
• Fog Pass (雾的计算)
  

<hr/>后处理 (Post Processing)

Common.hlsl

• ApplyTonemap (根据_TONEMAP_XXX宏使用对应的Tonemapping算法)
  
• ApplyColorGrading (LUT校色)
  
• ApplyFXAA (FXAA抗锯齿)
  

Bloom.shader

• Bloom Prefilter Pass (提取亮度)
  
• Bloom Blur Horizontal Pass (水平高斯模糊)
  
• Bloom Blur Vertical Pass (垂直高斯模糊)
  
• Bloom Upsample Pass (升采样)
  

UberPost.shader

• Bloom、Vignette、ColorGrading、FilmGrain、Dithering的结果合成 (P.S. FilmGrain、Dithering没有FinalPass才执行)
  

FinalPost.shader

• FXAA、FilmGrain、Dithering的结果合成 (P.S. FilmGrain、Dithering有FinalPass才执行)