???????: ????????????????????

Chengsoul

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??????????????????????????????????????????????????????????

???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

???????????????????????????????????????????????????????????????

?????????

??????????????????????????????????????????????????

� ??? Elden Ring

� ???? ???

� The Last of us Part I Remake

� The Last of us Part II

� ?????2

� Hogwarts: Legacy

??????????????????+?????????????????????????????????????????????????

� Far Cry 6

� ?????2

� ????? Death Stranding

????????????????????????????????????????????????????????????????????????????????????????

� ???????????????

� ????????????????

� ????????????????

????????????????????????????????????????????

??????????????????????????????????????????????(Shallow Water/Wave Equation)?????????????????UE5.1????

?????????????

????????UE5.1????????????????

?????

?????????????????????????????mesh????????????????????????????????????????????????????????????????????????????GPU??????????????????(Texture)??????????

????

Shallow Water Equation?????Shallow Wave Equation?????????????????????????????????????????????????????????????????????????????????????�???????�???????????????????????????????Wikipedia???https://en.wikipedia.org/wiki/Shallow_water_equations?????????Games103???https://www.bilibili.com/video/BV12Q4y1S73g/?p=10?????????????????????????????????????

??ViscosityConstant, ?: SWE constant, hN(t-1): Height sum of the nearest four points

???????????????????????h(t)???????h(t-1)?h(t-2)???????????????????????????Damping???????????????????1?????0-0.5???Damping???0-1????????????

????

??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

??????????????????????????Neumann boundary condition?https://en.wikipedia.org/wiki/Neumann_boundary_condition????????????????????0???????????????????????hN(t-1)????????????X???4????????????????????????4?????????4?????Y??????Y???????X?????????????????????????????????????????????????????????????????

1. <p>// Suppose Y is the point up to X. YIndex = XIndex + (0, 1)?</p><p>
   
2. </p><p>float XHeight = WaterPreHeight.Load(XIndex).x;</p><p>
   
3. </p><p>float YHeight = WaterPreHeight.Load(YIndex).x;</p><p>
   
4. </p><p>if (IsBoundary(YHeight))</p><p>
   
5. </p><p>{</p><p>
   
6. </p><p>YHeight = XHeight;</p><p>
   
7. </p><p>}</p>

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????

??????????????????

1. ???????????????????????????????

2. ?????????????

3. ???????

4. ????????????????

??????

???????????????????????????????????????????????????????????????GameThread????????????????????????????????????????????????????????????????????????????????????????????????????????????

?UE??????????SceneCaptureComponent????????????????????????????????????SceneCapture????????????????????????????????????????SceneCapture??????????Shader???????????????????????????????????????????????????????????????

???????????????????????pass?????????????????????????(ShadowDepth)?????UE?????https://docs.unrealengine.com/5.1/en-US/mesh-drawing-pipeline-in-unreal-engine/??

????????FParallelMeshDrawCommandPass???????????????DepthBuffer???????????????MeshProcessor?????CullingMode???????PS???????????????????????

????????Pass?????????????????????????SceneRenderer?????????????????????DrawCall????

???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

????????????????????????????????????????????????�?�?????????????????????ResolvePass????R8???????????????????????????

?UE Insight??????????9????????????ResolvePass??????0.08ms?????2080S???

????????????

??????????Pass?????????????????????????????????????????2?R8????????????????????????????+?????????????

??????????????????????????????????????????????????????????????????????????????????????????????????Games103???https://www.bilibili.com/video/BV12Q4y1S73g/?p=10?????????????????????????????

???????????????????????????float_max?????????

1. <p>if(bIsBoundary)</p><p>
   
2. </p><p>{</p><p>
   
3. </p><p>WaterHeight[SimulationIndex] = BOUNDARY_HEIGHT;</p><p>
   
4. </p><p>}</p><p>
   
5. </p><p>else</p><p>
   
6. </p><p>{</p><p>
   
7. </p><p>CapturedDepthVal = saturate(CapturedDepthVal);</p><p>
   
8. </p><p>float CurrentWaterHeight = WaterHeight[SimulationIndex];</p><p>
   
9. </p><p>// Object depth above water has no effect</p><p>
   
10. </p><p>WaterHeight[SimulationIndex] = CapturedDepthVal == 0.0f ? CurrentWaterHeight : min(CurrentWaterHeight, - CapturedDepthVal);</p><p>
    
11. </p><p>}</p>

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??????

???????????????????????????????????????Damping???????????????????????????????????????????????????????????????????????????????????????CS?????????????????????????????????????????????????PCG????????????Games103??????VirtualHeight????https://www.bilibili.com/video/BV12Q4y1S73g?t=4855.3&p=10????????????????

?????????????????????WaterLinePro????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

??Shader?????????2???????????????????1????????????????????CS/??PS????????????????ping-pong??????????????????????????????????

????????????????

1. <p>// Boundary pixels.</p><p>
   
2. </p><p>if(IsBoundary(PrevHeight))</p><p>
   
3. </p><p>{</p><p>
   
4. </p><p>// Skip iteration.</p><p>
   
5. </p><p>return;</p><p>
   
6. </p><p>}</p><p>
   
7. </p><p>// SWE</p><p>
   
8. </p><p>float NearHeight = UpPrevHeight + DownPrevHeight + LeftPrevHeight + RightPrevHeight;</p><p>
   
9. </p><p>float OutHeight = Damping * (PrevHeight + (PrevHeight - PrevPrevHeight) + TravelSpeed * 0.5f * (NearHeight - PrevHeight * 4));</p><p>
   
10. </p><p>// Store to output texture</p><p>
    
11. </p><p>OutWaterHeight[CurrentIndex] = OutHeight;</p>

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??????

?????????????????????????????????????

????????????????????

??????????ENQUEUE_RENDER_COMMAND??????????????????????????????????????????????????????????????????Normal/Displacement??????

??????????????????Normal?????????????????????PhotonWater???????Normal/Displacement Pass?????????????????????

????????????????????????????????????????????Norma?????????????????Mesh?????????????PhotonWater?????CDLOD???Mesh Tessellation?Screen-Space Displacement Mapping???????????????????????

???????????

??????????????????????????????????????????????????????????????????2??????????????????????????????????????????????????????????????????????????????????????????????

???????????????????????????????????????????????????????????????????????

?????????????????�??�??

??????????????????????????????????????????Mesh?????????????Clip???????????????????????BuildMeshDrawCommand??????CullMode?

1. <p>ERasterizerCullMode MeshCullMode = ComputeMeshCullMode(MaterialResource, OverrideSettings);</p><p>
   
2. </p><p>// Always render back faces</p><p>
   
3. </p><p>MeshCullMode = MeshCullMode == CM_CCW ? CM_CW : CM_CCW;</p><p>
   
4. </p><p>BuildMeshDrawCommmands(</p><p>
   
5. </p><p>...,</p><p>
   
6. </p><p>MeshCullMode,</p><p>
   
7. </p><p>...</p><p>
   
8. </p><p>);</p>

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??????PS???????????Pass???PS???????????????????????????????????????????????????????????????????????????

1. <p>// CustomCapturePS.usf</p><p>
   
2. </p><p>// Clip using water level, water level is already converted to device Z</p><p>
   
3. </p><p>clip(WaterLevelVal - SvPosition.z);</p>

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???????????????(Proxy)Mesh???????????????????????Hogwarts: Legacy?????????????????????????Mesh??????????????????Sphere/Capsule?????????????????????Artists???????????????????????????4????Attach??????????????Mesh????????????????

???Shader??

????????????Buffer???????????Buffer???????????????????1024x1024???????4096x4096?????????????????????????????????????????

� 3?????? R16F * 3

� ????????? R8 * 2

� ???????DS * 1

?????????Pass?

� ??????????)-CustomCapturePass

� ?????????????

� Resolve????-PhotonWaterCopyCaptureDepth

� ???????????-ComputeWaves

� ??????-IterateSWE

???1024X1024??????????UnrealInsight???????(2080S)?

????????????????????????????????????????????????????????????????

??????

???????????????????????PC/Console???????

?????????????????Pass??????????????????????S20??????????

� 1024x1024?????????????3ms?

� 512x512??????????????1ms???

???????????????????????????????????????????????????????????????????????256x256?????????????

???????????????

??????????????????????????????????????????????????????????????????????????????????????????????????????

???????????????????????????????????????????????????????????????????????

???????????????

??????????????????????????????????????????????

??????????????????????????????????????????????????????????????

??????????????????????????????????????????????????????????????????????????????????????

???????????????????????????????????????????2 (Red Dead Redemption 2)?????????????????

????????

??????????????????+flowmap?????????�??�???????????

?????2?

?????????

Cities Skylines:

Uncharted:

??Unreal????

??????Photon Water System???????????????????(flowmap)?????

????????????????????????????????????(Flowmap)????PhotonWater???????Flowmap??????????

????????????????????????????????????????????????????

????????????

?????????????????????????

???????????????????????

??????

??????????????????????????????????????????????????????????????????????????????????????????????????????????????????PhotonWater??Flowmap???????????????????????

????????????????????????????????????�???�??????????????????????????Flowmap Advection Pass??????????????????????????????Advection?????????????????????�??�???????????????????????????????????????????????

Advection

????????????????????????????/??/????????????????????????????????Flowmap??????????Advection????????????????????????????

???????????????????????????????????????????????????????????????????????????? https://www.youtube.com/watch?v=qsYE1wMEMPA??

???????????????????????????????????????????????????????????????????????????????????????4???????????GPU?????????

?????????????????????????????????????????????????????????????:

?????????????????????????????????????????????Sample?????????????????????????????????????Advection???????????????????GPU????????????

1. int2 CurrentIndex = dispatchThreadId.xy;
   
2. 
   
3. float2 FlowmapVector = GetFlowmapVec(CurrentIndex);
   
4. 
   
5. // Get traced back indices by -FlowmapVector
   
6. 
   
7. float2 TraceBackIndex = CurrentIndex - FlowmapVector * FlowmapStrength;
   
8. 
   
9. // Handle boundary conditions inside the bilinear sample
   
10. 
    
11. OutCurrentHeight[CurrentIndex] = BilinearSampleHeightsAtIndex(TraceBackIndex);
    
12. 
    
13. // We need to update history height at the same time because the simulation depends on two frames of history data.
    
14. 
    
15. OutHistoryHeight[CurrentIndex] = BilinearSampleHistoryHeightsAtIndex(TraceBackIndex);

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???????

????????????????????????????????Flowmap???Flowmap?????????????????????????????????

?????????????????????????????????????????????????????????????????????Volume Conservation??????????????Flowmap Advection??????????????????????????????????????????????????????????Damping???????????????????Damping????????????????????Flowmap????????damping????

????????Flowmap???Artists??????????????????????????Flowmap??

?????????????????????????????????????(Divergence)???(Curl)?????????????

?????????????Curl????????Divergence?????????????????????????????????????0????????????????????????????????????????????Helmholtz's theorem????????????????0???0???????

??????????????divergence-free?flowmap??????????????????????????????????????????????????????????????????????????https://youtu.be/qsYE1wMEMPA?list=PLi3obdsHfCiIjjfoF43df61WR1aXNhNID&t=699???????????https://en.wikipedia.org/wiki/Helmholtz_decomposition???????

?PhotonWater?????Flowmap???????????????????

????

?????????????????????????????????????????????????????????????????????Wrap???????????????????????????

????

???????Pass?Flowmap Advection?????????????????????????????????????Pass????????

???????????????????????????Flowmap?TextureSample??????????????????????????????????????????Flowmap???????????????????????????2080S???Pass GPU?????0.1ms??????????????????????????????????????

>>??
1. Games103?https://www.bilibili.com/video/BV12Q4y1S73g/?p=10? -??Surface Waves?SWE?????????
2. Waterline Pro Plugin?https://www.unrealengine.com/marketplace/en-US/product/waterline? -??????????????SceneCapture?????????????????
3. Kass, Michael, and Gavin Miller. "Rapid, stable fluid dynamics for computer graphics." Proceedings of the 17th annual conference on Computer graphics and interactive techniques. 1990.
4. But How DO Fluid Simulations Work? (https://www.youtube.com/watch?v=qsYE1wMEMPA) ????????Advection???
5. 3B1B???????? (https://www.youtube.com/watch?v=rB83DpBJQsE)
6. PhotonWater?GDC?? (https://www.youtube.com/watch?v=rB83DpBJQsE)???Flowmap?????

?/Byreave
?????????