From: kwolekr <kwolekr@minetest.net>
Date: Mon, 27 Apr 2015 08:05:25 +0000 (-0400)
Subject: Noise: Fix PcgRandom::randNormalDist() when range contains negative numbers
X-Git-Tag: 0.4.13~326
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=415167b228dea8b4108d7fe164c7fec8c061dcf5;p=oweals%2Fminetest.git

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 2e4588124..614234aa4 100644
--- 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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