A Practical Model for Subsurface Light Transport

1. A Practical Model for Subsurface Light Transport Henrik Wann Jensen Stephen R. Marschner Marc Levoy Pat Hanrahan

2. Outlines • Diffusion Theory • Measuring the BSSRDF • Rendering the BSSRDF • Results

3. Diffusion Theory

4. phase function mean cosine g:

5. first-order scattering of Lri：

6. Equation (1) scalar irradiance： vector irradiance： Light source：

7. Diffusion Approximation • The light distribution in highly scattering media tends to become isotropic. -----Equation (2)

8. Substituting equation2 into equation1 classic diffusion equation：

9. Boundary condition： ---equation (3)

10. Diffuse Fresnel reflectance Fr：Fresnel formula new boundary condition：

12. diffuse BSSRDF Rd Rd is equal to the radiant exitance divided by the incident flux subsurface reflection,which is often modeled as a semi-finite plane parallel medium.

13. The dipole method

14. (4) (5)

15. Single Scattering Term

16. ----flat surface

17. The BSSRDF Model

18. Measuring the BSSRDF

19. Rendering using the BSSRDF • Efficient integration of the BSSRDF including importance sampling • Single scattering evaluation for arbitrary geometry • Diffusion approximation for arbitrary geometry • Texture (spatial variation on the object surface).

20. Integrating the BSSRDF stochastically sampling the location of both endpoints of the shadow ray We sample the two terms of BSSRDF separately density：

21. Single scattering evaluation for arbitrary geometry • pick a random distance

22. Results