From e1cf41b94bcd30af56348befa7c06852d8474a6f Mon Sep 17 00:00:00 2001
From: Zode <jonzqzode@gmail.com>
Date: Wed, 17 Jul 2024 01:12:17 +0300
Subject: [PATCH] Fix Quaternion.FromDirection giving bogus output when fed a
 perfect down vector

---
 Source/Engine/Core/Math/Quaternion.cpp | 4 ++++
 Source/Engine/Core/Math/Quaternion.cs  | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/Source/Engine/Core/Math/Quaternion.cpp b/Source/Engine/Core/Math/Quaternion.cpp
index 03989dab5..5927e0665 100644
--- a/Source/Engine/Core/Math/Quaternion.cpp
+++ b/Source/Engine/Core/Math/Quaternion.cpp
@@ -294,6 +294,10 @@ Quaternion Quaternion::FromDirection(const Float3& direction)
     {
         RotationAxis(Float3::Left, PI_OVER_2, orientation);
     }
+    else if (Float3::Dot(direction, Float3::Down) >= 0.999f)
+    {
+        RotationAxis(Float3::Right, PI_OVER_2, orientation);
+    }
     else
     {
         Float3 right, up;
diff --git a/Source/Engine/Core/Math/Quaternion.cs b/Source/Engine/Core/Math/Quaternion.cs
index 86a6e4e2d..d4d0fe96c 100644
--- a/Source/Engine/Core/Math/Quaternion.cs
+++ b/Source/Engine/Core/Math/Quaternion.cs
@@ -654,6 +654,10 @@ namespace FlaxEngine
             {
                 orientation = RotationAxis(Float3.Left, Mathf.PiOverTwo);
             }
+            else if (Float3.Dot(direction, Float3.Down) >= 0.999f)
+            {
+                orientation = RotationAxis(Float3.Right, Mathf.PiOverTwo);
+            }
             else
             {
                 var right = Float3.Cross(direction, Float3.Up);