From e0e4b84e40cd7fd969e6f80f67193ad31b8670b0 Mon Sep 17 00:00:00 2001
From: Alexei Kotov <alexdobrohotov@yandex.ru>
Date: Fri, 24 May 2024 00:22:52 +0300
Subject: [PATCH] Disable specularity for negative lights

---
 components/sceneutil/lightcontroller.cpp | 12 +++++++++---
 components/sceneutil/lightcontroller.hpp |  2 ++
 components/sceneutil/lightutil.cpp       |  6 +++++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/components/sceneutil/lightcontroller.cpp b/components/sceneutil/lightcontroller.cpp
index caff6826f5..18b4580571 100644
--- a/components/sceneutil/lightcontroller.cpp
+++ b/components/sceneutil/lightcontroller.cpp
@@ -41,6 +41,7 @@ namespace SceneUtil
         if (mType == LT_Normal)
         {
             light->setDiffuse(mDiffuseColor);
+            light->setSpecular(mSpecularColor);
             traverse(node, nv);
             return;
         }
@@ -65,10 +66,10 @@ namespace SceneUtil
                 mPhase = mPhase <= 0.5f ? 1.f : 0.25f;
         }
 
-        osg::Vec4f result = mDiffuseColor * mBrightness * node->getActorFade();
+        const float result = mBrightness * node->getActorFade();
 
-        light->setDiffuse(result);
-        light->setSpecular(result);
+        light->setDiffuse(mDiffuseColor * result);
+        light->setSpecular(mSpecularColor * result);
 
         traverse(node, nv);
     }
@@ -78,4 +79,9 @@ namespace SceneUtil
         mDiffuseColor = color;
     }
 
+    void LightController::setSpecular(const osg::Vec4f& color)
+    {
+        mSpecularColor = color;
+    }
+
 }
diff --git a/components/sceneutil/lightcontroller.hpp b/components/sceneutil/lightcontroller.hpp
index 13f5501bf9..0c088d579f 100644
--- a/components/sceneutil/lightcontroller.hpp
+++ b/components/sceneutil/lightcontroller.hpp
@@ -27,12 +27,14 @@ namespace SceneUtil
         void setType(LightType type);
 
         void setDiffuse(const osg::Vec4f& color);
+        void setSpecular(const osg::Vec4f& color);
 
         void operator()(SceneUtil::LightSource* node, osg::NodeVisitor* nv);
 
     private:
         LightType mType;
         osg::Vec4f mDiffuseColor;
+        osg::Vec4f mSpecularColor;
         float mPhase;
         float mBrightness;
         double mStartTime;
diff --git a/components/sceneutil/lightutil.cpp b/components/sceneutil/lightutil.cpp
index f69461fa3c..8a38ee9b72 100644
--- a/components/sceneutil/lightutil.cpp
+++ b/components/sceneutil/lightutil.cpp
@@ -117,19 +117,23 @@ namespace SceneUtil
         configureLight(light, radius, isExterior);
 
         osg::Vec4f diffuse = esmLight.mColor;
+        osg::Vec4f specular = esmLight.mColor; // ESM format doesn't provide specular
         if (esmLight.mNegative)
         {
             diffuse *= -1;
             diffuse.a() = 1;
+            // Using specular lighting for negative lights is unreasonable
+            specular = osg::Vec4f();
         }
         light->setDiffuse(diffuse);
         light->setAmbient(ambient);
-        light->setSpecular(diffuse); // ESM format doesn't provide specular
+        light->setSpecular(specular);
 
         lightSource->setLight(light);
 
         osg::ref_ptr<SceneUtil::LightController> ctrl(new SceneUtil::LightController);
         ctrl->setDiffuse(light->getDiffuse());
+        ctrl->setSpecular(light->getSpecular());
         if (esmLight.mFlicker)
             ctrl->setType(SceneUtil::LightController::LT_Flicker);
         if (esmLight.mFlickerSlow)