GPU Pro 6

480 VI Compute

(a) (b) (c)

Figure 3.5. Volumetric obscurance using (a) ray tracing (256 rays/voxel), (b) mipmap

filtering, and (c) N-buffer filtering.

Please note that Equation (3.1) can be rewritten as

average

S

=

1

1 −

S

1

S

2



A

2

−



S

1

S

2



A

1



.

Consequently, only the average and the relative change in size (S

1

/S

2

) is needed

to deduce average

S

, which facilitates computations further. Imagine that each

cube is obtained by doubling the length of each edge of the predecessor. Then,

the ratio would be 1 : 8, resulting in average

S

=

8

7

(A

2

−

1

8

A

1

).

3.2.3 Fast Cube Averages

In the previous section, we assumed to have a quick method to determine the

average inside of a cube. Here, ...