1 / 21

BSSRDF: Bidirectional Surface Scattering Reflectance Distribution Functions

BSSRDF: Bidirectional Surface Scattering Reflectance Distribution Functions. Based on: "A Practical Model for Subsurface Light Transport" Henrik Wann Jensen, Steve Marschner, Marc Levoy and Pat Hanrahan. Jared M. Dunne C95 Adv. Graphics Feb. 7, 2002. What is BSSRDF?.

gstokes
Download Presentation

BSSRDF: Bidirectional Surface Scattering Reflectance Distribution Functions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BSSRDF: Bidirectional Surface Scattering ReflectanceDistribution Functions Based on: "A Practical Model for Subsurface Light Transport" Henrik Wann Jensen, Steve Marschner, Marc Levoy and Pat Hanrahan Jared M. Dunne C95 Adv. Graphics Feb. 7, 2002

  2. What is BSSRDF? • Bidirectional surface scattering reflectance distribution function • In other words… An equation that determines how incident light reflects and scatters from a surface • Also, simulates how light reflects off of and throughout a surface

  3. Example: Skin

  4. BRDF • Bidirectional reflectance distribution function • Simplification of BSSRDF • Assumes that light entering a material leaves it at the same point • Usually tries to approximate surface scattering in some way

  5. BSSRDF v. BRDF • BSSRDF allows simulation of light transport • Light can enter a material at one point and be reflected at another point. • BSSRDF  Translucence, Color Bleeding • BRDF  Opague, Hard-looking… • But… BSSRDF is EXPENSIVE

  6. BSSRDF v. BRDF BSSRDF BRDF

  7. Example BRDF BSSRDF

  8. The Theory • Outgoing radiance at point x0 is computed by integrating incident radiance at points xi over the surrounding area and incoming directions wi.

  9. Hendrik Wann Jensen et al • Basic Idea: Break into two parts • Diffuse = the radiance at a given point due to light transport within the media, via an approximation of the scatting • Single Scattering = the first order scattering from a surface… BRDF reflection + light refracted through the material

  10. Diffuse vs. Single Scatter

  11. The Diffusion Approximation • In highly scattering media (like milk), light scatters many times (often several hundred) • Causes a lot more calculations, more expensive (if you use full BSSRDF)

  12. Diff. Approx. (cont.) = Sd • It is observed that in such materials the scattering becomes isotropic (in all directions) even with a highly focused light distribution. • So the following two-term approximation is used: radiant fluence vector irradiance

  13. Single Scattering Term = S(1) • The light which refracts directly through or reflects off of the material • Directional component of incident light • Jensen (et al) extend a BRDF model (Hanrahan and Krueger) to achieve this scatter

  14. Putting the two together… • So Jensen’s model of BSSRDF becomes: • Or: • BSSRDF = Diffuse Approximation + Single Scatter Term

  15. Light propagation • sa= Absorption Coefficient • ss = Scattering Coefficient • st = Extinction Coefficient = sa +ss • These are used in the volume rendering equation, which describes how light moves through a medium

  16. Getting the Coefficients

  17. Got Milk?

  18. Marble bust 1.3 Million Triangles BRDF: 2 minutes BSSRDF: <5 minutes Monte Carlo: 1250 minutes

  19. Stanford Bunny

  20. Future Plans of Hendrik Wann Jensen • In an interview of Jensen by CGarchitect.com:“I would like to combine the BSSRDF with photon mapping, and also work on making these algorithms generally available and easy to use for complex models.”

  21. FinalRender • First Render Engine to support BSSRDF • More Info: http://trinity3d.comhttp://trinity3d.com/productinfo/FinalRender/finalrender.shtml

More Related