[PATCH] dsound: Correctly calculate angle between vectors with equal and opposite directions

[Andrew Eikum]

Signed-off-by: Andrew Eikum <aeikum(a)codeweavers.com>
---
 dlls/dsound/sound3d.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/dlls/dsound/sound3d.c b/dlls/dsound/sound3d.c
index 03fd3d4678..8dafa1dd64 100644
--- a/dlls/dsound/sound3d.c
+++ b/dlls/dsound/sound3d.c
@@ -111,6 +111,13 @@ static inline D3DVALUE AngleBetweenVectorsRad (const D3DVECTOR *a, const D3DVECT
 		return 0;
 
 	cos = product/(la*lb);
+	if(fabs(1 - cos) < 0.0001f){
+		angle = 0;
+	}else if(fabs(-1 - cos) < 0.0001f){
+		angle = M_PI;
+	}else{
+		angle = acos(cos);
+	}
 	angle = acos(cos);
 	TRACE("angle between (%f,%f,%f) and (%f,%f,%f) = %f radians (%f degrees)\n",  a->x, a->y, a->z, b->x,
 	      b->y, b->z, angle, RadToDeg(angle));
-- 
2.18.0