From 895dcf4aa6d856f672a09f37a7c02cb7f0c8608f Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Thu, 12 Mar 2026 00:00:28 +0100
Subject: [PATCH] Add auto-converting old point/spot lights brightness when
 using `Inverse Squared Falloff` to match new shader math

#3907
---
 Flax.flaxproj                             |  2 +-
 Source/Engine/Level/Actors/PointLight.cpp |  9 +++++++++
 Source/Engine/Level/Actors/SpotLight.cpp  | 10 ++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Flax.flaxproj b/Flax.flaxproj
index c9c27281b..78c03fce6 100644
--- a/Flax.flaxproj
+++ b/Flax.flaxproj
@@ -4,7 +4,7 @@
     "Major": 1,
     "Minor": 11,
     "Revision": 0,
-    "Build": 6807
+    "Build": 6808
   },
   "Company": "Flax",
   "Copyright": "Copyright (c) 2012-2026 Wojciech Figat. All rights reserved.",
diff --git a/Source/Engine/Level/Actors/PointLight.cpp b/Source/Engine/Level/Actors/PointLight.cpp
index 607bf1bc4..b5801166e 100644
--- a/Source/Engine/Level/Actors/PointLight.cpp
+++ b/Source/Engine/Level/Actors/PointLight.cpp
@@ -1,6 +1,7 @@
 // Copyright (c) Wojciech Figat. All rights reserved.
 
 #include "PointLight.h"
+#include "Engine/Content/Deprecated.h"
 #include "Engine/Graphics/RenderTask.h"
 #include "Engine/Graphics/RenderTools.h"
 #include "Engine/Graphics/RenderView.h"
@@ -196,6 +197,14 @@ void PointLight::Deserialize(DeserializeStream& stream, ISerializeModifier* modi
     DESERIALIZE(UseInverseSquaredFalloff);
     DESERIALIZE(UseIESBrightness);
     DESERIALIZE(IESBrightnessScale);
+
+    // [Deprecated on 12.03.2026, expires on 12.03.2028]
+    if (modifier->EngineBuild <= 6807 && SERIALIZE_FIND_MEMBER(stream, "UseInverseSquaredFalloff") != stream.MemberEnd() && UseInverseSquaredFalloff)
+    {
+        // Convert old non-physical brightness value that was used for Inverse Squared Falloff which wasn't based on proper cm/m units calculations
+        MARK_CONTENT_DEPRECATED();
+        Brightness = Math::Sqrt(Brightness * 0.01f);
+    }
 }
 
 bool PointLight::IntersectsItself(const Ray& ray, Real& distance, Vector3& normal)
diff --git a/Source/Engine/Level/Actors/SpotLight.cpp b/Source/Engine/Level/Actors/SpotLight.cpp
index 85b77647a..38502cf1b 100644
--- a/Source/Engine/Level/Actors/SpotLight.cpp
+++ b/Source/Engine/Level/Actors/SpotLight.cpp
@@ -1,6 +1,8 @@
 // Copyright (c) Wojciech Figat. All rights reserved.
 
 #include "SpotLight.h"
+
+#include "Engine/Content/Deprecated.h"
 #include "Engine/Graphics/RenderView.h"
 #include "Engine/Renderer/RenderList.h"
 #include "Engine/Content/Assets/IESProfile.h"
@@ -282,6 +284,14 @@ void SpotLight::Deserialize(DeserializeStream& stream, ISerializeModifier* modif
     DESERIALIZE(UseInverseSquaredFalloff);
     DESERIALIZE(UseIESBrightness);
     DESERIALIZE(IESBrightnessScale);
+
+    // [Deprecated on 12.03.2026, expires on 12.03.2028]
+    if (modifier->EngineBuild <= 6807 && SERIALIZE_FIND_MEMBER(stream, "UseInverseSquaredFalloff") != stream.MemberEnd() && UseInverseSquaredFalloff)
+    {
+        // Convert old non-physical brightness value that was used for Inverse Squared Falloff which wasn't based on proper cm/m units calculations
+        MARK_CONTENT_DEPRECATED();
+        Brightness = Math::Sqrt(Brightness * 0.01f);
+    }
 }
 
 bool SpotLight::IntersectsItself(const Ray& ray, Real& distance, Vector3& normal)