Fixed issue with incorrect sphere texture sampling

Adaptive Halton sampling. Min 4 spp, max 64 spp. 95% confidence, delta_max = 0.01. Time: 2s : 756ms

Adaptive Halton sampling. Min 4 spp, max 64 spp. 95% confidence, delta_max = 0.01. Time: 2s : 756ms

Adaptive Halton sampling. Min 4 spp, max 64 spp. 95% confidence, delta_max = 0.005. Time: 3s : 442ms

Adaptive Halton sampling. Min 4 spp, max 64 spp. 95% confidence, delta_max = 0.005. Time: 3s : 442ms

Adaptive Halton sampling. Min 4 spp, max 64 spp. 95% confidence, delta_max = 0.001. Time: 7s : 784ms

Adaptive Halton sampling. Min 4 spp, max 64 spp. 95% confidence, delta_max = 0.001. Time: 7s : 784ms

Halton, 64 samples. Time: 10s : 288ms

Halton, 16 samples. Time: 2s : 715ms

Halton, 4 samples. Time: 699ms

1000 random samples. Time: 320s : 482ms

4 random samples. Time: 742ms

1 Random sample. Time: 200ms