GPU Pro 6

4. Real-Time Rendering of Physically Based Clouds Using Precomputed Scattering 151

one to store the J

(n)

term, the other to store the current order scattering L

(n)

In

,

and the third to accumulate higher-order scattering. Note that these intermediate

tables cover the entire volume.

Computing every scattering order consists of three steps, as discussed in Sec-

tion 4.3.3. The first step is evaluating the J

(n)

term according to Equation (4.5).

This step is implemented by the shader shown in Listing 4.3.

The first step in this shader, like the prior shaders, retrieves the world-

space parameters from the 4D texture coordinates (lines 3–6). In the next

step,