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

kwolekr · kwolekr · commit 415167b228de · 2015-04-27T04:05:25.000-04:00
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
@@ -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);
 }
 
 ///////////////////////////////////////////////////////////////////////////////

Original file line number	Diff line number	Diff line change
`@@ -148,7 +148,7 @@ s32 PcgRandom::randNormalDist(s32 min, s32 max, int num_trials)`
`148`	`148`	`s32 accum = 0;`
`149`	`149`	`for (int i = 0; i != num_trials; i++)`
`150`	`150`	`accum += range(min, max);`
`151`		`- return ((float)accum / num_trials) + 0.5f;`
	`151`	`+ return round((float)accum / num_trials);`
`152`	`152`	`}`
`153`	`153`
`154`	`154`	`///////////////////////////////////////////////////////////////////////////////`