GPU Pro 5

132 II Lighting and Shading

g = 0.0

g = 0.3

g = 0.5

g = 0.7

g = 0.8

0.12

0.06

–180° 0° 180°

Figure 3.6. Henyey-Greenstein phase function result for different values of g.

in the atmosphere that cause the light to scatter, but for practical reasons we use

a constant value for it which can be tweaked by artists.

Then, we calculate the scattering factor f

SF

for a certain view angle as

f

SF

(θ)=f

HG

(θ) · scattering amount. (3.2)

3.3 Low-Resolution Rendering

The straightforward ray-marching approach we use is nice because it’s relatively

simple to implement. However, the drawback is that we need quite a lot of

samples to make it look good. The more samples we take,