Chapter 14. Advanced Techniques for Realistic Real-Time Skin Rendering

Chapter 14. Advanced Techniques for Realistic Real-Time Skin Rendering

1. The Appearance of Skin2. An Overview of the Skin-Rendering System3. Specular Surface Reflectance4. Scattering Theory5. Advanced Subsurface Scattering6. A Fast Bloom Filter7. Conclusion0. KeywordsSubsurface scattering Human skin and facesPhysically accurate models Real-time implementation1. The Appearance of Skin . ., , , , . .Whats missing?(a) (b) ?

A Multilayer Skin Model 2 .Surface reflectanceSubsurface scattering Subsurface scattering diffuse term Approximation Approximation .Skin Surface Reflectance , 6% (White) . , , .BRDF .

Skin Subsurface Reflectance subsurface .Sub-surface , , , , . 2-layered .2. An Overview of the Skin-Rendering System 3 Analytic BRDF (Kelemen and Szirmay-Kalos 2001) 4 Diffusion profiles 5 6 subsurface scattering .BRDF

3. Specular Surface Reflectance , .BRDF .

Comparing the Kelemen/Szirmay-Kalos Specular BRDF to the Phong ModelspecularLight+=lightColor[i]*lightShadow[i]*rho_s* specBRDF(N,V,L[i],eta,m)*saturate(dot(N,L[i]));Specular ModelComparing Direct Computation of the Specular Model to the Fast Version

Models of microfacetsPhong distribution

Gaussian distribution

Beckmann distribution

where m is the average slope of the surface microfacets.Beckmann Texture

Computing Kelemen BRDF

rho_sTorrance/Sparrow specular BRDF model with the Beckmann microfacet distribution functionA survey of human faces presented by Weyrich et al.4. Scattering Theory BRDF . () ?

Diffusion Profile scattering approximation . .

Diffusion Profile .

Reflectance

R(r) = 0.070G(0.036, r) + 0.18G(0.14, r) + 0.21G(0.91, r) + 0.29G(7.0, r)Adequate parameters

Figure 14-13 Our Sum-of-Gaussians Parameters for a Three-Layer Skin ModelFigure 14-14 Plot of the Sum-of-Gaussians Fit for a Three-Layer Skin Model5. Advanced Subsurface Scattering

Irradiance Texture

Why we use six Gaussians

Visualizing Diffusion of RGB

Figure 14-19 Visualizing Diffusion in Skin for Red, Green, and Blue LightThe Final Shader

Final Image