• Blinn-Torrance-Sparrow (1977)
  - isotropic reflectors with smooth microstructure
• Cook-Torrance (1982)
  - wavelength dependent Fresnel term
• He-Torrance-Sillion-Greenberg (1991)
  - adds polarization, statistical microstructure, self-reflectance

Very little of this work has made its way into graphics H/W. Why?