its ultra-photorealistic digital look-alikes. The team was the first in the world to isolate the subsurface scattering component (a specialized case of BTDF) using the simplest light stage, consisting on moveable light source, moveable high-res digital camera, 2 polarizers in a few positions and really simple algorithms on a modest computer. The team utilized the existing scientific knowledge that light that is reflected and scattered from the air-to-oil layer retains its polarization while light that travels within the skin loses its polarization. The subsurface scattering component can be simulated as a steady high-scatter glow of light from within the models, without which the skin does not look realistic. ESC Entertainment, a company set up by Warner Brothers Pictures specially to do the visual effects / virtual cinematography system for The Matrix Reloaded and The Matrix Revolutions isolated the parameters for an approximate analytical BRDF which consisted of Lambertian diffusion component and a modified specular Phong component with a Fresnel type of effect. Overview of the BxDF functions BRDF (Bidirectional reflectance distribution function) is a simplified BSSRDF, assuming that light enters and leaves at the same point (see the image on the right). BTDF (Bidirectional transmittance distribution function) is similar to BRDF but for the opposite side of the surface. (see the top image). BDF (Bidirectional distribution function) is collectively defined by BRDF and BTDF. BSSRDF (Bidirectional scattering-surface reflectance distribution function or Bidirectional surface scattering RDF) describes the relation between outgoing radiance and the incident flux, including the phenomena like subsurface scattering (SSS). The BSSRDF describes how light is transported between any two rays that hit a surface. BSSTDF (Bidirectional scattering-surface transmittance distribution function) is like BTDF but with subsurface scattering. BSSDF (Bidirectional scattering-surface distribution function) is collectively defined by BSSTDF and BSSRDF. Also known as BSDF (Bidirectional scattering distribution function). See also BRDF Radiometry Reflectance Radiance BTF References Radiometry Astrophysics 3D rendering