# Lit 光照

### Include

```
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/FragInputs.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/ShaderPass.cs.hlsl"

#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitProperties.hlsl"

#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Material.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/Lighting.hlsl"

#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/LightLoopDef.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/Lit.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/LightLoop.hlsl"

#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/ShaderPass/LitSharePass.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Lit/LitData.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/ShaderPassForward.hlsl"
```

物体表面信息

```
struct SurfaceData
{
    half3 albedo;
    half3 specular;
    half  metallic;
    half  smoothness;
    half3 normalTS;
    half3 emission;
    half  occlusion;
    half  alpha;
    half  clearCoatMask;
    half  clearCoatSmoothness;
};
```

一些杂项效果效果和优化光照的信息

```
struct BuiltinData
{
    real opacity;
    real alphaClipTreshold;
    real3 bakeDiffuseLighting;
    real3 backBakeDiffuseLighting;
    real shadowMask0;
    real shadowMask1;
    real shadowMask2;
    real shadowMask3;
    real3 emissiveColor;
    real2 motionVector;
    real2 distortion;
    real distortionBlur;
    uint isLightmap;
    uint renderingLayers;
    float depthOffset;
    #if defined(UNITY_VIRTUAL_TEXTURING)
    real4 vtPackedFeedback;
    #endif
};
```

顶点着色器输出的顶点位置信息

```
struct PositionInputs
{
    float3 positionWS;  // World space position (could be camera-relative)
    float2 positionNDC; // Normalized screen coordinates within the viewport    : [0, 1) (with the half-pixel offset)
    uint2  positionSS;  // Screen space pixel coordinates                       : [0, NumPixels)
    uint2  tileCoord;   // Screen tile coordinates                              : [0, NumTiles)
    float  deviceDepth; // Depth from the depth buffer                          : [0, 1] (typically reversed)
    float  linearDepth; // View space Z coordinate                              : [Near, Far]
};
```

**bidirectional scattering distribution function** 光线双向传播分布函数所需参数

```
struct BSDFData
{
    uint materialFeatures;
    real3 diffuseColor;
    real3 fresnel0;
    real ambientOcclusion;
    real specularOcclusion;
    float3 normalWS;
    real perceptualRoughness;
    real coatMask;
    uint diffusionProfileIndex;
    real subsurfaceMask;
    real thickness;
    bool useThickObjectMode;
    real3 transmittance;
    float3 tangentWS;
    float3 bitangentWS;
    real roughnessT;
    real roughnessB;
    real anisotropy;
    real iridescenceThickness;
    real iridescenceMask;
    real coatRoughness;
    real3 geomNormalWS;
    real ior;
    real3 absorptionCoefficient;
    real transmittanceMask;
};
```

预计算光照参数

```
// Precomputed lighting data to send to the various lighting functions
struct PreLightData
{
    float NdotV;                     // Could be negative due to normal mapping, use ClampNdotV()

    // GGX
    float partLambdaV;
    float energyCompensation;

    // IBL
    float3 iblR;                     // Reflected specular direction, used for IBL in EvaluateBSDF_Env()
    float  iblPerceptualRoughness;

    float3 specularFGD;              // Store preintegrated BSDF for both specular and diffuse
    float  diffuseFGD;

    // Area lights (17 VGPRs)
    // TODO: 'orthoBasisViewNormal' is just a rotation around the normal and should thus be just 1x VGPR.
    float3x3 orthoBasisViewNormal;   // Right-handed view-dependent orthogonal basis around the normal (6x VGPRs)
    float3x3 ltcTransformDiffuse;    // Inverse transformation for Lambertian or Disney Diffuse        (4x VGPRs)
    float3x3 ltcTransformSpecular;   // Inverse transformation for GGX                                 (4x VGPRs)

    // Clear coat
    float    coatPartLambdaV;
    float3   coatIblR;
    float    coatIblF;               // Fresnel term for view vector
    float    clearCoatIndirectSpec;  // Weight used to support the clear coat's SSR/IBL blending
    float3x3 ltcTransformCoat;       // Inverse transformation for GGX                                 (4x VGPRs)

#if HAS_REFRACTION
    // Refraction
    float3 transparentRefractV;      // refracted view vector after exiting the shape
    float3 transparentPositionWS;    // start of the refracted ray after exiting the shape
    float3 transparentTransmittance; // transmittance due to absorption
    float transparentSSMipLevel;     // mip level of the screen space gaussian pyramid for rough refraction
#endif
};
```


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