From 3d84a147f0ae781a71f74d9d7ad0b07f9b1ccb43 Mon Sep 17 00:00:00 2001
From: Alexander Gavriliuk <alexandrgproductengine@lindenlab.com>
Date: Fri, 14 Jun 2024 08:06:31 +0200
Subject: #1611 Regression in anti-flipping mechanism for mouselook camera

---
 indra/llmath/v2math.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'indra/llmath/v2math.cpp')

diff --git a/indra/llmath/v2math.cpp b/indra/llmath/v2math.cpp
index ecbfe7378c..78d349f2f0 100644
--- a/indra/llmath/v2math.cpp
+++ b/indra/llmath/v2math.cpp
@@ -67,7 +67,14 @@ F32 angle_between(const LLVector2& a, const LLVector2& b)
     return angle;
 }
 
-BOOL are_parallel(const LLVector2 &a, const LLVector2 &b, float epsilon)
+F32 signed_angle_between(const LLVector2& a, const LLVector2& b)
+{
+    F32 angle = angle_between(a, b);
+    F32 rhombus_square = a[VX] * b[VY] - b[VX] * a[VY];
+    return rhombus_square < 0 ? -angle : angle;
+}
+
+BOOL are_parallel(const LLVector2 &a, const LLVector2 &b, F32 epsilon)
 {
     LLVector2 an = a;
     LLVector2 bn = b;
-- 
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