???????????

?? · 发表于 2019-12-9 11:05:00

?GPU Gems 3???�Chapter 14. Advanced Techniques for Realistic Real-Time Skin Rendering�??????????????????????????????????????????????????

????????????GPU Gems 3???????????????????????????????????????

????GPU Gems 3???????????????????????????????????????????????????????????????????????????????????????????

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

???????20?????????????????????

??????????Subsurface Light Transport, SSLT?[2001]
?????Diffusion Profile? [2001]
????dipole? [2001]
???????Texture Space Blur?[2003]
????multipole? [2005]
???????Screen Space Blur????????????SSSSS,Screen Space SubSurface Scattering?[2009]
??????????Path-Traced Subsurface Scattering???????Ray Marching?[2009]
?????????Pre-Integrated Skin Shading?[2010]
??????????SSSS,Separable Subsurface Scattering?[2015]
?

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

???????????????????????????????????????????????????20???????????????????????

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

??????????5?????????????????????????????????????????????????????????

OK??????????????????????????

??????5????

??????5???????

?????4??

? ?????4???????

?????????

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

??????????????? UE4?Siren?

? ???Siren????? @UE4

??????????

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

????????????????????????????????????????????????????????????????????????????????????????????????94%????????????6%????

? ??????

?????????????????????????????[Krishnaswamy and Baranoski 2004]???????????????????????????????????????????????epidermis?????????????[Poirer 2004]?????????????????????????????????????????????????????????????????????specular???Donner?Jensen[Donner and Jensen 2005]?2005??????????????????????????????????????

? ??????

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

???????BRDF(bidirectional reflectance distribution function)????????????????????????BSSDF?

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

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

?????specular reflection?
??????subsurface scattering?

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

3.1 ?????specular reflection?

??????specular reflection?????????Gems 3???Kelemen and Szirmay-Kalos specular BRDF???????????????Kelemen and Szirmay-Kalos specular BRDF????Torrance-Sparrow?????????????????????????????????????????????????????

3.2 ??????Subsurface Scattering?

3.2.1 ????????????Translucent and Subsurface Scattering?

???????????????????????????????????????????????????????????????????????(Subsurface Light Transport,SSLT)??[Pharr 2010]????????

???????????????????????????????????????????6%?????????????????????????????????????94%??????????????????????????????????????????????????????????????????????

????????????????????????????????????????????3D??????????????????????????????????Transmittance??

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

??????????Jensen?2001?????A Practical Model for Subsurface Light Transport??????????????????????????????????????????????????????????????????????????????????????????????

3.2.2 BRDF?BSSRDF

????????????????Volumetric Path Tracing?Volumetric Photon Mapping?BSSRDF?

???BSSRDF?Bidirectional Surface Scattering Reflectance Distribution Function???????????????????????

???????? BRDF ??? BSSRDF??????BSSRDF?BRDF????????BSSRDF????????????????????

?? BRDF?BSSRDF????????????

??BRDF???????????????????????????????????BSSRDF??????????????????????????????????????

??BSSRDF?????

????????????????????????????????????????????BSSRDF??????????????????????????????????????????????????????????????????????????????????????BSSRDF?????????????????????????????????????????????????????????????:

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

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

3. ?????????????

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

???????????????????????????????????????????????????????????????????????????????BSSRDF????????????

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

??? ????

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

3.2.3 BTDF????Transmittance?

????????????????????????????????????????????????????????????????????Transmittance????????????????????

? ???Transmittance????

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

????????BTDF?????????? Bidirectional Transmittance Distribution Function?????

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

BRDF??????????Bidirectional Reflectance Distribution Function?
BSSRDF?????????????, Bidirectional Surface Scattering Reflectance Distribution Function?
BTDF?????????? Bidirectional Transmittance Distribution Function?
BSDF??????????Bidirectional Scattering Distribution Function?

???????????????https://zhuanlan.zhihu.com/p/27014447???BRDF?BTDF?BSDF????????????????????

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

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

???

BRDF??????????????radiance????????????irradiance?????????????????????????????????????????BRDF??
BTDF??????????????????????????????????????????BTDF??
BSDF?????????????????????????????????????????BSDF???BSDF = BRDF + BTDF?

? BSDF = BRDF + BTDF

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

?1?????????????????

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

?3????????BTDF?????????????BTDF????????????????????

????GPU Gems 3??????????????????Translucent Shadow Maps?TSMs?????????????????????????????????

3.2.4 ??BRDF?BSSRDF?BTDF?BSDF???

????????PPT???????BRDF?BSSRDF?BTDF?BSDF????

? BRDF?BSSRDF?BTDF?BSDF???

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

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

?????????BRDF??
?????????? BSSRDF??
???????BTDF??

??????

?????BRDF ? BSSRDF ?????
BSDF???????????????BSDF = BRDF + BTDF

???????Diffusion Profile?

?????Diffusion Profile??????????????????????

???????????Diffusion Profiles????????????Diffusion Profiles???????????????????????????????Diffusion Profiles?????????????????????????????????????????????????????�????�??Diffusion Profiles??????????????Diffusion ??Diffuse Scattering???????????????????????????

??????????diffusion profile??????????????????????????

?????diffusion profile?????????????????�??�???????????LUT?????????????????????�???�??????????????????????????

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

?????????????diffusion profile???????????????Dipole????????Multipole????????Sum-of-Gaussians?????????????????Diffusion Profiles???????

?????????????????????????????????????????????????????????????????????????????????????RGB????????????????????diffusion profile????????????????(??)???

??????????diffusion profile??????????????????????????????????????????????

????????????????????????????????????????????????????????????????????(a)???

?????diffusion profile?????????????????????????? ??????????????????????????????????????

??????????????????????????????(b)???

? ????????diffusion profile?

?????????RGB?????????????????????????????????????????????????????????????????????????????

??????2001??Jensen ?????????[Jensen et al.2001]????????????????????????????????????dipole??????????????

????????????????????r???????????????????????????????????????????????????

? ?r?????????diffusion??????

???????????????dipole????????????????dipole?????????????????????????????????Dipole Profiles?????????dipole??????????diffusion profile??

? ?????????????????????[Jensen 2001]

??????????R(r)???????????????????????????????????R(r)??????????????

?1???????????????????????r=0??????????????????????????????????????????????????????

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

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

?1?????????????????

?2????????diffusion profile???1??????????????????????????????????

4.1 ????Multipole???

???????????diffusion profile??????????????Dipole??????Multipole??????Sum-of-Gaussians???????????????Diffusion Profiles???????

2005??Donner and Jensen?????Light Diffusion in Multi-Layered Translucent Materials?[Donner and Jensen 2005]?????multipole????????diffusion profiles?????????????????????????

??????????????????????????????2\^n????????????????????????????n=0????????n=1???????Dipole??n=2???????n?2????????Multipole??

? ?????????????????????????????[Donner 2005]

????????????diffusion profile????????????Light Diffusion in Multi-Layered Translucent Materials??http://jbit.net/~sparky/layered.pdf

4.2 ?????????Sum-of-Gaussians Diffusion Profile?

????????????????????????????e^-r2????????????????????????????????????????????????????????????????????????????diffusion profile??

? ????????diffusion profile?

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

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

????????R(r)?????????w i???v i?k??????

??????????v???????

????1/?2v???G?v?r??????2D??????????????????????????unit impulse response???

??????????diffusion profile???????????????????????????????

????[Jensen et al. 2001]?????????

? ??????????????Dipole Profile?

???????2???????Profile???????4??????????????Profile???????????

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

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

??????????????????????????????????????????????http://gad.qq.com/article/detail/33372????Matlab??????????????????,??https://cn.mathworks.com/help/curvefit/gaussian.html

Matlab??????????????8???????1????2??3??2?????????????

? Matlab???????

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

4.3 ??????????????A Sum-of-Gaussians Fit for Skin?

???????????????Sum-of-Gaussians Diffusion Profile???????????????????????????????????

????????????????????????Dipole Profile??????????????????????????????Dipole Profile????????????????????????Dipole???????3?????Dipole?????????????????3?????Dipole???????Jensen?????????????Profile???

?3???????Dipole Profile?????????????????4????????????????????????6????????????????

????????????Matlab?????????????6???????3?Dipole Profile?RGB????????????????????????????????????????

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

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

????????????????????????1.0??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

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

??????????diffusion profile??????????????????????????

???????diffusion profile????????????????????????????????????????????????????????

?????????????????diffusion profile????????????????????????????????????

???????Texture Space Blur?
???????Screen Space Blur?

???????????

5.1 ???????Texture Space Blur?

????????Texture-Space Diffusion???????Texture Space Blur????????????[Borshukov and Lewis 2003]???????????????????????????????????????subsurface scattering??

??????????????????????????????????????3D????2D?????????????

? ?????????????????????Texture Space Blur???????

GDC 2007?????NVIDIA?talk �Advanced Skin Rendering�?http://developer.download.nvidia ... /Advanced_Skin.pdf.??????Texture Space Blur?????Gems 3????????

??????????6???????????????????Dipole???????????????????Texture Space Blur????????????????????????????????????????????6????????????????????????????????????????????

? ?GPU Gems 3????????????Texture Space Blur?????

???????Texture Space Blur???Combining blurs?????shader?????

float3 diffuseLight= nonBlur* E1 * pow( diffuseCol, 0.5 );

float3 blur2tap = f3tex2D( blur2Tex, v2f.c_texCoord.xy );

float3 blur4tap = f3tex2D( blur4Tex, v2f.c_texCoord.xy );

float3 blur8tap = f3tex2D( blur8Tex, v2f.c_texCoord.xy );

float3 blur16tap = f3tex2D( blur16Tex, v2f.c_texCoord.xy );

float3 blur32tap = f3tex2D( blur32Tex, v2f.c_texCoord.xy );

diffuseLight+= blur2 * blur2tap.xyz;

diffuseLight+= blur4 * blur4tap.xyz;

diffuseLight+= blur8 * blur8tap.xyz;

diffuseLight+= blur16 * blur16tap.xyz;

diffuseLight+= blur32 * blur32tap.xyz;

// renormalize weights so they sum to 1.0

float3 norm2 = nonBlur+ blur2 + blur4 + blur8 + blur16 + blur32;

diffuseLight/= norm2;

diffuseLight*= pow( diffuseCol, 0.5 );

5.2 ???????Screen Space Blur?[2009]

???????Screen Space Blur? [Jimenez et al.2009]???????????????Screen Space SubSurfaceScattering??SSSSS?

? ?????????Screen Space Blur?????

????????Texture Space Blur?????????????Screen Space Blur?[Jimenez et al.2009]??????Stencil????Skin??????????Blur??????????????????

??????????Stencil??????????????????????????????Diffusion Profile????????????????????????d(x,y)??????dFdx(d(x,y))?dFdy(d(x,y))?????

? ???????Screen Space Blur?????

? ???????Screen Space Blur??????

? ???????Screen Space Blur?

?????????????????????????????????????????????????????????????????????????????????????Diffusion Profile?????????????????

??????????

6.1 ????????Translucent Shadow Maps?TSMs?

?GPU Gems 3???????????????Translucent Shadow Maps?TSMs?????????????????

???????????Texture-Space Diffusion??????????????????????????????????????????????????????GPU Gems 3????????????Translucent Shadow Maps?TSMs?(Dachsbacher and Stamminger 2004)????????????????????????????????????

? ?GPU Gems 3?????Translucent Shadow Maps????

? ??????????

???ShaderX7??�Real-Time Subsurface Scattering using Shadow Maps�??????????????Shadow Maps???????????????

? Rendering AAA-QualityCharacters of Project �A1� @ NDC 2016 Programming Session

6.2 ?????????Pre-Integrated Skin Rendering?

?????????Pre-Integrated Skin Shading???GPU Pro 2??� Pre-Integrated Skin Shading�?????????????

?????????Pre-Integrated Skin Shading?????????????????????????????????????????????????????dot(N,L)???????????????????????????

? ?????????Pre-Integrated Skin Shading????

??????????????????????|??????????????N�L??????BRDF???The diffuse BRDF lookup?|?????????BRDF????r??????????????

???????????????????????Texture-Space Diffusion????????????????????????????????????

? ???????????????Texture-Space Diffusion???

???????15?????????????????????????????????????

? ?? Pre-Integrated Skin Shading??????15???????????????????????????

???????????Pre-Integrated Skin Rendering??????????GPU Pro 2???� Pre-Integrated Skin Shading�???

6.3 SSSS,??????????Separable Subsurface Scattering?

??????Subsurface Scattering????SSS,?3S????????????Separable Subsurface Scattering??????SSSS?4S, Separable Subsurface Scattering??Jimenez???2015??????????[Jimenez J 2015]?

??????????????Screen Space Blur???????????Texture Space Blur???????6???????12?pass(?????????????????)?

???Jorge????GDC 2013,?talk�Next-Generation Character Rendering�?http://www.iryoku.com/images/pos ... ndering-Teaser.pptx???????SSSS???????2015??????????SSSS(?????????,Separable Subsurface Scattering)(http://iryoku.com/separable-sss)??????????2?Pass????????????????????????????Unreal?????????

? ??????Separable Convolution?

? ??SSSS????? @GDC 2013 by Activision-Blizzard

??Separable Subsurface Scattering?????SSSS??? @ COMPUTER GRAPHICS forum 2015 by Jorge Jimenez @ Activision-Blizzard

6.4 ??????????Path-Traced Subsurface Scattering???????Ray Marching?

??????????Path-Traced Subsurface Scattering?????????????????Monte-Carlo Subsurface Scattering??????????????????????????????????????Ray Marching??????

?SIGGRAPH 2017 Course: Physically Based Shading in Theory and Practice????�Volumetric Skin and Fabric Shading at Framestore�?http://blog.selfshadow.com/publi ... olumetric_notes.pdf????????????????Course??????????????????????

???NDC 2016 Programming Session??Rendering AAA-QualityCharacters of Project�A1�?????????PPT?????

? Rendering AAA-QualityCharacters of Project �A1� @ NDC 2016 Programming Session

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

https://www.cs.rpi.edu/~cutler/c ... _projects/white.pdf

6.5 Deferred Single Scattering

??????????????????????PPT:

? Rendering AAA-QualityCharacters of Project �A1� @ NDC 2016 Programming Session

????????

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

1. ??????

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

?????specular reflection?
??????subsurface scattering?

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

2. ??????

?????specular reflection???????????

Torrance-Sparrow
Kelemen and Szirmay-Kalos specular BRDF
??????????

???Kelemen and Szirmay-Kalos specular BRDF????Torrance-Sparrow???????????????????

3. ???????

3.1 ?????Diffusion Profile?

?????diffusion profile??????????????????????????

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

????Dipole???
????Multipole???
????Sum-of-Gaussians???

???????????????Diffusion Profiles??????????????diffusion profile?????????????????????????????????????????????????????????????????????????diffusion profile?????????????????

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

???????Texture Space Blur?
???????Screen Space Blur??????????????Screen Space SubSurfaceScattering??SSSSS?

3.2 ????????

????????Translucent Shadow Maps?TSMs?
?????????Pre-Integrated Skin Rendering?
??????????SSSS , Separable Subsurface Scattering?
??????????Path-Traced Subsurface Scattering???????Ray Marching?
Deferred Single Scattering

4. ?????????

??????????Subsurface Light Transport, SSLT?[2001]
?????Diffusion Profile? [2001]
????dipole? [2001]
???????Texture Space Blur?[2003]
????multipole? [2005]
???????Screen Space Blur????????????SSSSS,Screen Space SubSurface Scattering?[2009]
??????????Path-Traced Subsurface Scattering???????Ray Marching?[2009]
?????????Pre-Integrated Skin Shading?[2010]
??????????SSSS,Separable Subsurface Scattering?[2015]
?

?????GitHub?

????????GitHub????????????

???MarkDown????????????????????????????????GitHub??????????????????????????????????Git?????????????????????,???????????????GitHub?Repo????

????GitHub???????

QianMo/Game-Programmer-Study-Notesgithub.com

??????

[1] Eugene d'Eon, David Luebke. GPU Gems 3, Chapter 14. Advanced Techniques for Realistic Real-Time Skin Rendering,2007.(https://developer.nvidia.com/gpugems/GPUGems3/gpugems3_ch14.html)
[2] Volumetric Skin and Fabric Shading at Framestore , SIGGRAPH 2017 Course: Physically Based Shading in Theory and Practice?http://blog.selfshadow.com/publi ... olumetric_notes.pdf?
[3] Rendering AAA-QualityCharacters of Project �A1�, NDC 2016 Programming Session
[4] https://zhuanlan.zhihu.com/p/27014447
[5] http://gad.qq.com/article/detail/33372
[6] http://gad.qq.com/article/detail/33373
[7] http://www.iryoku.com/next-generation-life
[8] https://gamingbolt.com/final-fan ... e-pre-rendered-ones
[9] Next-Generation-Character-Rendering ?GDC 2013 http://www.iryoku.com/images/pos ... ndering-Teaser.pptx
[10] https://en.wikipedia.org/wiki/Bi ... stribution_function
[11] Jensen, Henrik Wann, Stephen R. Marschner, Marc Levoy, and Pat Hanrahan.2001. "A Practical Model for Subsurface Light Transport." In Proceedings of SIGGRAPH 2001.
[12] Matlab online doc https://cn.mathworks.com/help/curvefit/gaussian.html
[13]d'Eon, Eugene."NVIDIA Demo Team Secrets�Advanced Skin Rendering." Presentation at Game Developer Conference 2007. http://developer.download.nvidia ... /Advanced_Skin.pdf.
[14] Jorge Jimenez, K�roly Zsolnai, etc. Separable Subsurface Scattering(http://iryoku.com/separable-sss/)
[15] Faceworks https://github.com/NVIDIAGameWorks/FaceWorks
[16] Colin Barre-Brisebois,Marc Bouchard. 2011. Presentation at Game Developer Conference 2011. https://colinbarrebrisebois.com/ ... ce-scattering-look/
[17] Jorge Jimenez, David Whelan, etc. Real-Time Realistic Skin Translucency(http://iryoku.com/translucency/d ... in-Translucency.pdf)
[18] orge Jimenez. Next Gen Character Rendering GDC 2013.
[19] Koki Nagano?Graham Fyffe?Oleg Alexander etc."Skin Microstructure Deformation with Displacement Map Convolution"http://gl.ict.usc.edu/Research/SkinStretch/
[20] RenderDoc. https://github.com/baldurk/renderdoc
[21] Per H. Christensen, Brent Burley. "Approximate Reflectance Profiles for Efficient Subsurface Scattering" Presentation at SIGGRAPH 2015. https://graphics.pixar.com/library/ApproxBSSRDF/paper.pdf
[22] Per H. Christensen, Brent Burley. "Approximate Reflectance Profiles for Efficient Subsurface Scattering" Presentation at SIGGRAPH 2015. https://graphics.pixar.com/library/ApproxBSSRDF/paper.pdf

??????
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