87 lines
4.0 KiB
Markdown
87 lines
4.0 KiB
Markdown
---
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title: 未命名
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date: 2025-03-27 17:37:02
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excerpt:
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tags:
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rating: ⭐
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---
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# Toon Lumen
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## 抹平法线思路
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### ViewVector Fix WorldNormal
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参考：
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- [【UE5】环境光与GI 2：抹平法线](https://zhuanlan.zhihu.com/p/25839790454)
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在`LumenScreenProbeGather.usf`中对法线进行抹平处理。其Pass位于
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- DiffuseIndirectAndAO
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- LumenScreenProbeGather
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- Integrate
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- SimpleDiffuse/SupportImportanceSampleBRDF?/SupportAll?
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在如下位置添加代码：
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```c++
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if (IsValid(Material))
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{
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const float2 ScreenUV = (Coord.SvPosition + 0.5f) * View.BufferSizeAndInvSize.zw;
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const float3 WorldPosition = GetWorldPositionFromScreenUV(ScreenUV, Material.SceneDepth);
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const float3 WorldNormal = Material.WorldNormal;
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//BlueRose Modify
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if (Material.ShadingID == SHADINGMODELID_TOONSTANDARD)
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{
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//使用Yu-ki016的方法“抹平法线”
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float3 V = normalize(LWCHackToFloat(PrimaryView.WorldCameraOrigin) - WorldPosition);
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const uint ToonDataAssetID = GetToonDataAssetIDFromGBuffer(Material.GBufferData);
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float DiffuseIndirectLightingFlatten = GetDiffuseIndirectLightingFlatten(ToonDataAssetID);
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Material.WorldNormal = normalize(lerp(WorldNormal, V, DiffuseIndirectLightingFlatten));
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}
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//BlueRose Modify End
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...
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}
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}
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```
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该方法存在一些问题：**当相机围绕角色旋转时，角色身上的 GI变化会比较明显**。
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### 低频化WorldNormal & Spherical Harmonics
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参考：
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- [[UFSH2024]用虚幻引擎5为《幻塔》定制高品质动画流程风格化渲染管线 | 晨风 Neverwind 完美世界游戏】【精准空降到 12:55】](https://www.bilibili.com/video/BV1rW2LYvEox/?share_source=copy_web&vd_source=fe8142e8e12816535feaeabd6f6cdc8e&t=775)
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- [[UFSH2024]用虚幻引擎5为《幻塔》定制高品质动画流程风格化渲染管线 | 晨风 Neverwind 完美世界游戏】 【精准空降到 36:52】](https://www.bilibili.com/video/BV1rW2LYvEox/?share_source=copy_web&vd_source=fe8142e8e12816535feaeabd6f6cdc8e&t=2212)
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- [ ] 需要实现：法线平滑 => 饱和度平滑。（没说细节，不清楚算法）
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- [[UFSH2024]用虚幻引擎5为《幻塔》定制高品质动画流程风格化渲染管线 | 晨风 Neverwind 完美世界游戏】【精准空降到 35:09】](https://www.bilibili.com/video/BV1rW2LYvEox/?share_source=copy_web&vd_source=fe8142e8e12816535feaeabd6f6cdc8e&t=2109)
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- [ ] 小于等于High存储的是一个八面体，提前加一个Pass进行平滑：采样法线方向半球面的平均数值。
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- [ ] 大于等于Epic存储的是一个三阶球谐，保持1阶球谐数值不变，对2~3阶球谐按照系数进行平滑。并且添加能量补偿，大致与PBR的结果接近。
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![[Lumen_SHData.png|800]]
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![[Lumen_能量补偿1.png|800]]
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![[Lumen_能量补偿2.png|800]]
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UE5中采样球谐贴图方法(ReflectionEnvironmentShared.ush)：
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```c++
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/**
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* Computes sky diffuse lighting from the SH irradiance map.
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* This has the SH basis evaluation and diffuse convolution weights combined for minimal ALU's - see "Stupid Spherical Harmonics (SH) Tricks"
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*/
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float3 GetSkySHDiffuse(float3 Normal)
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{
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float4 NormalVector = float4(Normal, 1.0f);
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float3 Intermediate0, Intermediate1, Intermediate2;
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Intermediate0.x = dot(SkyIrradianceEnvironmentMap[0], NormalVector);
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Intermediate0.y = dot(SkyIrradianceEnvironmentMap[1], NormalVector);
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Intermediate0.z = dot(SkyIrradianceEnvironmentMap[2], NormalVector);
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float4 vB = NormalVector.xyzz * NormalVector.yzzx;
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Intermediate1.x = dot(SkyIrradianceEnvironmentMap[3], vB);
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Intermediate1.y = dot(SkyIrradianceEnvironmentMap[4], vB);
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Intermediate1.z = dot(SkyIrradianceEnvironmentMap[5], vB);
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float vC = NormalVector.x * NormalVector.x - NormalVector.y * NormalVector.y;
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Intermediate2 = SkyIrradianceEnvironmentMap[6].xyz * vC;
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// max to not get negative colors
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return max(0, Intermediate0 + Intermediate1 + Intermediate2);
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}
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```
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## Cel适配
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需要实现Cel多光源方案。
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大致的思路就是Copy Lumen结果，之后在[[Toon多光源参考|Toon多光源Pass]]中提取亮度，再根据亮度采样Ramp计算光影结果。 |