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206 lines
6.9 KiB
Plaintext
206 lines
6.9 KiB
Plaintext
---
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title: Shader API
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---
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## 通用 API
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API 调用方式如下：
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```glsl
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#include "Common.glsl"
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float f2 = pow2(0.5);
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```
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### Common
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提供了`PI` 等常用宏，`gammaToLinear`、`pow2` 等通用方法，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/Common.glsl)。
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### Fog
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提供了深度雾化方法:
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```glsl
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vec4 fog(vec4 color, vec3 positionVS);
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```
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### Transform
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提供了模型空间、视图空间、世界空间、相机坐标等[系统变量](/docs/graphics/material/variables/):
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```glsl
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mat4 renderer_LocalMat;
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mat4 renderer_ModelMat;
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mat4 camera_ViewMat;
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mat4 camera_ProjMat;
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mat4 renderer_MVMat;
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mat4 renderer_MVPMat;
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mat4 renderer_NormalMat;
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vec3 camera_Position;
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vec3 camera_Forward;
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vec4 camera_ProjectionParams;
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```
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### Light
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提供了获取[引擎光照](/docs/graphics/light/light)，包括直接光、间接光的方法:
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```glsl
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// 直接光
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DirectLight getDirectLight(int index);
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PointLight getPointLight(int index);
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SpotLight getSpotLight(int index);
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// 间接光
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EnvMapLight scene_EnvMapLight;
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#ifdef SCENE_USE_SH
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vec3 scene_EnvSH[9];
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#endif
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#ifdef SCENE_USE_SPECULAR_ENV
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samplerCube scene_EnvSpecularSampler;
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#endif
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```
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### Normal
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提供了法线计算的一些通用方法：
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```glsl
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// 在切线空间进行法线贴图运算后的法线
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vec3 getNormalByNormalTexture(mat3 tbn, sampler2D normalTexture, float normalIntensity, vec2 uv, bool isFrontFacing);
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// 利用导数计算切线，针对本身没有切线的模型
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mat3 getTBNByDerivatives(vec2 uv, vec3 normal, vec3 position, bool isFrontFacing);
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```
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### Shadow
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提供了阴影相关的函数，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/Shadow.glsl)。
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```glsl
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// 获取级联阴影所属层级，比如级联数量设为4，则返回 0～3
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int computeCascadeIndex(vec3 positionWS);
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// 获取 shadowmap 中的坐标
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vec3 getShadowCoord(vec3 positionWS);
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// 获取阴影强度，包含采样方式、阴影衰减
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float sampleShadowMap(vec3 positionWS, vec3 shadowCoord);
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```
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### Skin
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提供骨骼计算方法：
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```glsl
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mat4 getSkinMatrix(Attributes attributes);
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```
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### BlendShape
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提供 BS 计算方法：
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```glsl
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void calculateBlendShape(Attributes attributes, inout vec4 position, inout vec3 normal, inout vec4 tangent);
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```
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## PBR API
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除了通用 API，PBR 也封装了一些列如 `BSDF` 光照模型的 API，用户拓展别的材质时可以尝试 `#include` 复用这些 API。
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### AttributesPBR
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封装了 PBR 所需要的所有 Attribute 变量，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/AttributesPBR.glsl)。
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### VaryingsPBR
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封装了 PBR 所需要的所有 Varyings 变量，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/VaryingsPBR.glsl)。
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### LightDirectPBR
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封装了基于 BSDF 光照模型的直接光计算，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/LightDirectPBR.glsl)。
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一般来说，直接调用即可：
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```glsl
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// Evaluate direct lighting
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evaluateDirectRadiance(varyings, surfaceData, bsdfData, shadowAttenuation, totalDiffuseColor, totalSpecularColor);
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```
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提供了以下函数重载宏覆盖光照模型的关键计算：
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```glsl
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#define FUNCTION_SURFACE_SHADING surfaceShading
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#define FUNCTION_DIFFUSE_LOBE diffuseLobe
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#define FUNCTION_SPECULAR_LOBE specularLobe
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#define FUNCTION_CLEAR_COAT_LOBE clearCoatLobe
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#define FUNCTION_SHEEN_LOBE sheenLobe
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void surfaceShading(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, vec3 incidentDirection, vec3 lightColor, inout vec3 totalDiffuseColor, inout vec3 totalSpecularColor);
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void diffuseLobe(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, vec3 attenuationIrradiance, inout vec3 diffuseColor);
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void specularLobe(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, vec3 incidentDirection, vec3 attenuationIrradiance, inout vec3 specularColor);
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float clearCoatLobe(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, vec3 incidentDirection, vec3 color, inout vec3 specularColor);
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void sheenLobe(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, vec3 incidentDirection, vec3 attenuationIrradiance, inout vec3 diffuseColor, inout vec3 specularColor);
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```
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### LightInDirectPBR
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封装了基于 BSDF 光照模型的[环境光](/docs/graphics/light/ambient)计算，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/LightIndirectPBR.glsl)。
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一般来说，直接调用即可：
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```glsl
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// IBL
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evaluateIBL(varyings, surfaceData, bsdfData, totalDiffuseColor, totalSpecularColor);
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```
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提供了以下函数重载宏覆盖光照模型的关键计算：
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```glsl
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#define FUNCTION_DIFFUSE_IBL evaluateDiffuseIBL
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#define FUNCTION_SPECULAR_IBL evaluateSpecularIBL
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#define FUNCTION_CLEAR_COAT_IBL evaluateClearCoatIBL
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#define FUNCTION_SHEEN_IBL evaluateSheenIBL
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void evaluateDiffuseIBL(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, inout vec3 diffuseColor);
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void evaluateSpecularIBL(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, float radianceAttenuation, inout vec3 outSpecularColor);
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float evaluateClearCoatIBL(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, inout vec3 specularColor);
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void evaluateSheenIBL(Varyings varyings, SurfaceData surfaceData, BSDFData bsdfData, float radianceAttenuation, inout vec3 diffuseColor, inout vec3 specularColor);
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```
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### VertexPBR
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PBR 顶点着色器所需要的一些方法，比如获取 TilingOffset 之后的 UV 坐标，获取骨骼、BS运算过后的世界坐标、法线、切线等，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/VertexPBR.glsl)。
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```glsl showLineNumbers
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VertexInputs vertexInputs = getVertexInputs(attributes);
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gl_Position = renderer_MVPMat * vertexInputs.positionOS;
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```
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### BSDF
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PBR 光照模型关键文件，封装了 BRDF、投射、折射等相关的通用计算函数， 以及用于后续光照模型计算的 `SurfaceData` 结构体和 `BSDFData` 结构体，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/BSDF.glsl)。
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### FragmentPBR
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包含了大量 CPU 传过来的金属度、粗糙度、贴图等变量，通过 `getSurfaceData` 初始化 `SurfaceData` 结构体，详见[源码](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/FragmentPBR.glsl)。
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```glsl showLineNumbers
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BSDFData bsdfData;
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// 初始化 SurfaceData 结构体
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SurfaceData surfaceData = getSurfaceData(varyings, aoUV, gl_FrontFacing);
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// 可以在这加工 SurfaceData 里面的数据
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initBSDFData(surfaceData, bsdfData);
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```
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### 最后
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除了关键 API 的功能和调用方式，关于整个文件的组织方式可以参考官网的 [ForwardPassPBR](https://github.com/galacean/engine/blob/main/packages/shader/src/shaders/shadingPBR/ForwardPassPBR.glsl)。
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