Fix exterior sun direction/position (bug #4898)

CHANGELOG.md

@@ -16,6 +16,7 @@
     Bug #4754: Stack of ammunition cannot be equipped partially
     Bug #4816: GetWeaponDrawn returns 1 before weapon is attached
     Bug #4822: Non-weapon equipment and body parts can't inherit time from parent animation
+    Bug #4898: Odd/Incorrect lighting on meshes
     Bug #5057: Weapon swing sound plays at same pitch whether it hits or misses
     Bug #5062: Root bone rotations for NPC animation don't work the same as for creature animation
     Bug #5066: Quirks with starting and stopping scripted animations

apps/openmw/mwrender/renderingmanager.cpp

@@ -716,6 +716,9 @@ namespace MWRender
         // need to wrap this in a StateUpdater?
         mSunLight->setPosition(osg::Vec4(position.x(), position.y(), position.z(), 0));
 
+        // The sun is not synchronized with the sunlight because sunlight origin can't reach the horizon
+        // This is based on exterior sun orbit and won't make sense for interiors, see WeatherManager::update
+        position.z() = 400.f - std::abs(position.x());
         mSky->setSunDirection(position);
 
         mPostProcessor->getStateUpdater()->setSunPos(mSunLight->getPosition(), mNight);

apps/openmw/mwworld/weather.cpp

@@ -752,21 +752,21 @@ namespace MWWorld
             const float dayDuration = adjustedNightStart - mSunriseTime;
             const float nightDuration = 24.f - dayDuration;
 
-            double theta;
+            float orbit;
             if (!is_night)
             {
-                theta = static_cast<float>(osg::PI) * (adjustedHour - mSunriseTime) / dayDuration;
+                float t = (adjustedHour - mSunriseTime) / dayDuration;
+                orbit = 1.f - 2.f * t;
             }
             else
             {
-                theta = static_cast<float>(osg::PI)
-                    - static_cast<float>(osg::PI) * (adjustedHour - adjustedNightStart) / nightDuration;
+                float t = (adjustedHour - adjustedNightStart) / nightDuration;
+                orbit = 2.f * t - 1.f;
             }
 
-            osg::Vec3f final(static_cast<float>(cos(theta)),
-                -0.268f, // approx tan( -15 degrees )
-                static_cast<float>(sin(theta)));
-            mRendering.setSunDirection(final * -1);
+            // Hardcoded constant from Morrowind
+            const osg::Vec3f sunDir(-400.f * orbit, 75.f, -100.f);
+            mRendering.setSunDirection(sunDir);
             mRendering.setNight(is_night);
         }