Physically Based Rendering, 3rd Edition

15: Light Transport II: Volume Rendering

Just as BSDFs characterize reflection from the surfaces in a scene, Medium class implementations represent scattering that occurs between surfaces; examples include atmospheric scattering effects such as haze, absorption in a stained glass window, or scattering by fat globules in a bottle of milk. Technically, all of these phenomena are due to surface interactions with a vast number of microscopic particles, though it is preferable to find a less cumbersome way of modeling them than considering them individually. With the models described in this chapter, the particles are assumed to be so numerous that they can be represented using statistical distributions instead of an explicit enumeration.

This chapter ...