GPU Pro 5

106 II Lighting and Shading

coefficient over the path, which is given by the following equation:

T (A → B)=



B

A

(β

e

R

e

−h(t)/H

R

+ β

e

M

e

−h(t)/H

M

)dt. (2.1)

Scattering by molecules and aerosols happens independently and is propor-

tional to the corresponding scattering coefficient (β

s

R/M

)atsealevelandtothe

particle density scale factor (e

−h/H

R/M

)atP. The fraction of scattered light

going in the view direction is given by the phase function p

R/M

(θ)foreachtype.

Light in-scattered at P is attenuated on the way to the camera by a factor of

e

−T (P →C)

. Finally, to account for shadowing, we also need to introduce a visi-

bility term V (P ), which equals 1 if P is visible ...