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Fix #108316: CUDA error rendering Attic scene

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The light tree dependent on the first threshold to evaluate to 1
when picking up an emitter.

Pull Request: https://projects.blender.org/blender/blender/pulls/108323
This commit is contained in:
Sergey Sharybin 2023-05-27 14:19:19 +02:00
parent bdf5649f36
commit 50ba227740
1 changed files with 17 additions and 2 deletions
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19
intern/cycles/kernel/light/tree.h
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@ -509,6 +509,19 @@ ccl_device void sample_resevoir(const int current_index,
return;
}
total_weight += current_weight;
/* When `-ffast-math` is used it is possible that the threshold is almost 1 but not quite.
* For this case we check the first assignment explicitly (instead of relying on the threshold to
* be 1, giving it certain probability). */
if (selected_index == -1) {
selected_index = current_index;
selected_weight = current_weight;
/* The threshold is expected to be 1 in this case with strict mathematics, so no need to divide
* the rand. In fact, division in such case could lead the rand to exceed 1 because of division
* by something smaller than 1. */
return;
}
float thresh = current_weight / total_weight;
if (rand <= thresh) {
selected_index = current_index;
@ -518,8 +531,10 @@ ccl_device void sample_resevoir(const int current_index,
else {
rand = (rand - thresh) / (1.0f - thresh);
}
kernel_assert(rand >= 0.0f && rand <= 1.0f);
return;
/* Ensure the `rand` is always within 0..1 range, which could be violated above when
* `-ffast-math` is used. */
rand = saturatef(rand);
}
/* Pick an emitter from a leaf node using resevoir sampling, keep two reservoirs for upper and