An Optical Model for Translucent Volume Rendering and Its Implementation Using the Preintegrated Shear-Warp Algorithm

Table 1

Important terms used in the paper.

Symbol	Definition
𝑥	Space coordinate of a voxel
𝑠, 𝑙	Distance along the view direction
𝑥(𝑠)	3D coordinate along the view direction
𝜔	View direction
𝜔^′	Ray direction
𝐼(x,𝜔)	Intensity at position 𝑥 along 𝜔
𝑇(𝑠,𝑙)	Attenuation from 𝑥(𝑠) to 𝑥(𝑙) along the view direction
𝜏	Attenuation coefficient
𝑅(𝑥)	Surface reflectivity color in position 𝑥
𝐵𝑠(𝑥)	Value of Blinn-Phong surface shading model
𝑆	Scattering lighting intensity
𝑟(x,𝜔,𝜔^′)	A bi-directional reflection distribution function (BRDF).
𝑔	Ray direction
𝐿𝑔	Intensity of light source
𝑙𝑔	Distance along ray direction
𝑑	Direct scattering
𝑖	Indirect scattering