48 lines
2.1 KiB
Markdown
48 lines
2.1 KiB
Markdown
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---
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title: 自定义材质输出节点
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date: 2022-09-02 11:30:37
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excerpt:
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tags:
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rating: ⭐
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---
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## 前言
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参考文章：https://zhuanlan.zhihu.com/p/163121357
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## 自定义材质输出节点
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继承`UMaterialExpressionCustomOutput`类并实现对应函数即可。
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具体可以参考`BentNormal`材质输出节点。Shader代码位于BasePassPixelShader.usf的ApplyBentNormal()，CPP代码位于UMaterialExpressionBentNormalCustomOutput类中（UE4.27）。这种节点会生成`NUM_MATERIAL_OUTPUTS_节点名`的宏。
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之后就可以在BasePassPixelShader.usf中通过宏与函数获取到对应的节点计算结果。比如：
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```c++
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void ApplyBentNormal( in FMaterialPixelParameters MaterialParameters, in float Roughness, inout float3 BentNormal, inout float DiffOcclusion, inout float SpecOcclusion )
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{
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#if NUM_MATERIAL_OUTPUTS_GETBENTNORMAL > 0
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#if MATERIAL_TANGENTSPACENORMAL
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BentNormal = normalize( TransformTangentVectorToWorld( MaterialParameters.TangentToWorld, GetBentNormal0(MaterialParameters) ) );
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#else
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BentNormal = GetBentNormal0(MaterialParameters);
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#endif
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FSphericalGaussian HemisphereSG = Hemisphere_ToSphericalGaussian( MaterialParameters.WorldNormal );
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FSphericalGaussian NormalSG = ClampedCosine_ToSphericalGaussian( MaterialParameters.WorldNormal );
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FSphericalGaussian VisibleSG = BentNormalAO_ToSphericalGaussian( BentNormal, DiffOcclusion );
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FSphericalGaussian DiffuseSG = Mul( NormalSG, VisibleSG );
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float VisibleCosAngle = sqrt( 1 - DiffOcclusion );
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#if 1 // Mix full resolution normal with low res bent normal
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BentNormal = DiffuseSG.Axis;
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//DiffOcclusion = saturate( Integral( DiffuseSG ) / Dot( NormalSG, HemisphereSG ) );
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DiffOcclusion = saturate( Integral( DiffuseSG ) * 0.42276995 );
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#endif
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float3 N = MaterialParameters.WorldNormal;
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float3 V = MaterialParameters.CameraVector;
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SpecOcclusion = DotSpecularSG( Roughness, N, V, VisibleSG );
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SpecOcclusion /= DotSpecularSG( Roughness, N, V, HemisphereSG );
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SpecOcclusion = saturate( SpecOcclusion );
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#endif
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}
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```
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