Noise: Fix PcgRandom::randNormalDist() when range contains negative numbers

This fixes an issue with erroneous float-to-int rounding that resulted in
truncation toward 0, causing a biased distribution.

diff --git a/src/noise.cpp b/src/noise.cpp
index 2e4588124213be8566cff2b1abb095b689646607..614234aa4c52bbf9370fe86f85ecf4f63be3eff1 100644 (file)
--- a/src/noise.cpp
+++ b/src/noise.cpp
@@ -148,7 +148,7 @@ s32 PcgRandom::randNormalDist(s32 min, s32 max, int num_trials)
        s32 accum = 0;
        for (int i = 0; i != num_trials; i++)
                accum += range(min, max);
-       return ((float)accum / num_trials) + 0.5f;
+       return round((float)accum / num_trials);
 }
 
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