add white ambient to spell VFX as in Morrowind

CHANGELOG.md

@@ -18,6 +18,7 @@
     Bug #4602: Robert's Bodies: crash inside createInstance()
     Bug #4700: Editor: Incorrect command implementation
     Bug #4744: Invisible particles must still be processed
+    Bug #4949: Incorrect particle lighting
     Bug #5088: Sky abruptly changes direction during certain weather transitions
     Bug #5100: Persuasion doesn't always clamp the resulting disposition
     Bug #5120: Scripted object spawning updates physics system

apps/openmw/mwrender/animation.cpp

@@ -7,6 +7,7 @@
 #include <osg/BlendFunc>
 #include <osg/Material>
 #include <osg/Switch>
+#include <osg/LightModel>
 
 #include <osgParticle/ParticleSystem>
 #include <osgParticle/ParticleProcessor>
@@ -372,6 +373,19 @@ namespace
     private:
         int mEffectId;
     };
+
+    osg::ref_ptr<osg::LightModel> getVFXLightModelInstance()
+    {
+        static osg::ref_ptr<osg::LightModel> lightModel = nullptr;
+
+        if (!lightModel)
+        {
+            lightModel = new osg::LightModel;
+            lightModel->setAmbientIntensity({1,1,1,1});
+        }
+
+        return lightModel;
+    }
 }
 
 namespace MWRender
@@ -1547,7 +1561,9 @@ namespace MWRender
         parentNode->addChild(trans);
 
         osg::ref_ptr<osg::Node> node = mResourceSystem->getSceneManager()->getInstance(model, trans);
-        node->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
+
+        // Morrowind has a white ambient light attached to the root VFX node of the scenegraph
+        node->getOrCreateStateSet()->setAttributeAndModes(getVFXLightModelInstance(), osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
 
         SceneUtil::FindMaxControllerLengthVisitor findMaxLengthVisitor;
         node->accept(findMaxLengthVisitor);