GPU Pro 6

4. Physically Based Light Probe Generation on GPU 263

0.0

1

0

BRDF IS

ENV IS

128

0

128

0

0

128

64

64

0.5 1.00.75

Roughness

0.25

Figure 4.17. Number of samples in each method for a specular probe.

0.0 0.25 0.5

Roughness

0.75 1.0

Figure 4.18. The ground truth render using 10,000 samples.

thermore, we only use environment map importance sampling when the roughness

is greater than 0.7. With lower roughness values, BRDF importance sampling

worked well alone. Figure 4.17 shows the number of samples for both methods

with different roughness values.

Listing 4.6 demonstrates the final preintegration function that uses the com-

bination of both methods.

Using the combined importance ...