Fix interior sun direction (bug #7585)

CHANGELOG.md

@@ -89,6 +89,7 @@
     Bug #7553: Faction reaction loading is incorrect
     Bug #7557: Terrain::ChunkManager::createChunk is called twice for the same position, lod on initial loading
     Bug #7573: Drain Fatigue can't bring fatigue below zero by default
+    Bug #7585: Difference in interior lighting between OpenMW with legacy lighting method enabled and vanilla Morrowind
     Bug #7603: Scripts menu size is not updated properly
     Bug #7604: Goblins Grunt becomes idle once injured
     Bug #7609: ForceGreeting should not open dialogue for werewolves

apps/openmw/mwrender/renderingmanager.cpp

@@ -693,8 +693,9 @@ namespace MWRender
         osg::Vec4f diffuse = SceneUtil::colourFromRGB(cell.getMood().mDirectionalColor);
 
         setSunColour(diffuse, diffuse, 1.f);
-
-        const osg::Vec4f interiorSunPos = osg::Vec4f(-0.15f, 0.15f, 1.f, 0.f);
+        // This is total nonsense but it's what Morrowind uses
+        static const osg::Vec4f interiorSunPos
+            = osg::Vec4f(-1.f, osg::DegreesToRadians(45.f), osg::DegreesToRadians(45.f), 0.f);
         mPostProcessor->getStateUpdater()->setSunPos(interiorSunPos, false);
         mSunLight->setPosition(interiorSunPos);
     }