Implement vanilla-style wind speed calculations (bug #4449)

CHANGELOG.md

@@ -27,6 +27,7 @@
     Bug #4383: Bow model obscures crosshair when arrow is drawn
     Bug #4384: Resist Normal Weapons only checks ammunition for ranged weapons
     Bug #4411: Reloading a saved game while falling prevents damage in some cases
+    Bug #4449: Value returned by GetWindSpeed is incorrect
     Bug #4540: Rain delay when exiting water
     Bug #4600: Crash when no sound output is available or --no-sound is used.
     Bug #4639: Black screen after completing first mages guild mission + training

apps/openmw/mwrender/sky.cpp

@@ -1625,7 +1625,8 @@ void SkyManager::updateRainParameters()
 {
     if (mRainShooter)
     {
-        float windFactor = mWindSpeed/3.f;
+        // Note: an arbitrary value. An original engine seems to use a different approach to rotate raindrops.
+        float windFactor = mWindSpeed/32.f;
         float angle = windFactor * osg::PI/4;
         mRainShooter->setVelocity(osg::Vec3f(0, mRainSpeed * windFactor, -mRainSpeed));
         mRainShooter->setAngle(angle);

apps/openmw/mwrender/sky.hpp

@@ -68,6 +68,8 @@ namespace MWRender
         float mDLFogOffset;
 
         float mWindSpeed;
+        float mCurrentWindSpeed;
+        float mNextWindSpeed;
 
         float mCloudSpeed;
 

apps/openmw/mwworld/weather.cpp

@@ -538,6 +538,8 @@ WeatherManager::WeatherManager(MWRender::RenderingManager& rendering, MWWorld::E
     , mMasser("Masser")
     , mSecunda("Secunda")
     , mWindSpeed(0.f)
+    , mCurrentWindSpeed(0.f)
+    , mNextWindSpeed(0.f)
     , mIsStorm(false)
     , mPrecipitation(false)
     , mStormDirection(0,1,0)
@@ -663,6 +665,40 @@ void WeatherManager::playerTeleported(const std::string& playerRegion, bool isEx
     }
 }
 
+osg::Vec3f WeatherManager::calculateStormDirection()
+{
+    osg::Vec3f playerPos (MWMechanics::getPlayer().getRefData().getPosition().asVec3());
+    playerPos.z() = 0;
+    osg::Vec3f redMountainPos (25000, 70000, 0);
+    osg::Vec3f stormDirection = (playerPos - redMountainPos);
+    stormDirection.normalize();
+
+    return stormDirection;
+}
+
+float WeatherManager::calculateWindSpeed(int weatherId, float currentSpeed)
+{
+    float targetSpeed = std::min(8.0f * mWeatherSettings[weatherId].mWindSpeed, 70.f);
+    if (currentSpeed == 0.f)
+        currentSpeed = targetSpeed;
+
+    float multiplier = mWeatherSettings[weatherId].mRainEffect.empty() ? 1.f : 0.5f;
+    float updatedSpeed = (Misc::Rng::rollClosedProbability() - 0.5f) * multiplier * targetSpeed + currentSpeed;
+
+    if (updatedSpeed > 0.5f * targetSpeed && updatedSpeed < 2.f * targetSpeed)
+    {
+        currentSpeed = updatedSpeed;
+    }
+
+    // Take in account direction to the Red Mountain, when needed
+    if (weatherId == 6 || weatherId == 7)
+    {
+        currentSpeed = (calculateStormDirection() * currentSpeed).length();
+    }
+
+    return currentSpeed;
+}
+
 void WeatherManager::update(float duration, bool paused, const TimeStamp& time, bool isExterior)
 {
     MWWorld::ConstPtr player = MWMechanics::getPlayer();
@@ -695,12 +731,21 @@ void WeatherManager::update(float duration, bool paused, const TimeStamp& time,
     {
         mRendering.setSkyEnabled(false);
         stopSounds();
+        mWindSpeed = 0.f;
+        mCurrentWindSpeed = 0.f;
+        mNextWindSpeed = 0.f;
         return;
     }
 
     calculateWeatherResult(time.getHour(), duration, paused);
 
+    if (!paused)
+    {
         mWindSpeed = mResult.mWindSpeed;
+        mCurrentWindSpeed = mResult.mCurrentWindSpeed;
+        mNextWindSpeed = mResult.mNextWindSpeed;
+    }
+
     mIsStorm = mResult.mIsStorm;
 
     // For some reason Ash Storm is not considered as a precipitation weather in game
@@ -709,11 +754,7 @@ void WeatherManager::update(float duration, bool paused, const TimeStamp& time,
 
     if (mIsStorm)
     {
-        osg::Vec3f playerPos (player.getRefData().getPosition().asVec3());
+        mStormDirection = calculateStormDirection();
-        playerPos.z() = 0;
-        osg::Vec3f redMountainPos (25000, 70000, 0);
-        mStormDirection = (playerPos - redMountainPos);
-        mStormDirection.normalize();
         mRendering.getSkyManager()->setStormDirection(mStormDirection);
     }
 
@@ -1096,7 +1137,9 @@ inline void WeatherManager::calculateResult(const int weatherID, const float gam
 
     mResult.mCloudTexture = current.mCloudTexture;
     mResult.mCloudBlendFactor = 0;
-    mResult.mWindSpeed = current.mWindSpeed;
+    mResult.mNextWindSpeed = 0;
+    mResult.mWindSpeed = mResult.mCurrentWindSpeed = calculateWindSpeed(weatherID, mWindSpeed);
+
     mResult.mCloudSpeed = current.mCloudSpeed;
     mResult.mGlareView = current.mGlareView;
     mResult.mAmbientLoopSoundID = current.mAmbientLoopSoundID;
@@ -1180,7 +1223,11 @@ inline void WeatherManager::calculateTransitionResult(const float factor, const
     mResult.mFogDepth = lerp(current.mFogDepth, other.mFogDepth, factor);
     mResult.mDLFogFactor = lerp(current.mDLFogFactor, other.mDLFogFactor, factor);
     mResult.mDLFogOffset = lerp(current.mDLFogOffset, other.mDLFogOffset, factor);
-    mResult.mWindSpeed = lerp(current.mWindSpeed, other.mWindSpeed, factor);
+
+    mResult.mCurrentWindSpeed = calculateWindSpeed(mCurrentWeather, mCurrentWindSpeed);
+    mResult.mNextWindSpeed = calculateWindSpeed(mNextWeather, mNextWindSpeed);
+
+    mResult.mWindSpeed = lerp(mResult.mCurrentWindSpeed, mResult.mNextWindSpeed, factor);
     mResult.mCloudSpeed = lerp(current.mCloudSpeed, other.mCloudSpeed, factor);
     mResult.mGlareView = lerp(current.mGlareView, other.mGlareView, factor);
     mResult.mNightFade = lerp(current.mNightFade, other.mNightFade, factor);

apps/openmw/mwworld/weather.hpp

@@ -325,6 +325,8 @@ namespace MWWorld
         MoonModel mSecunda;
 
         float mWindSpeed;
+        float mCurrentWindSpeed;
+        float mNextWindSpeed;
         bool mIsStorm;
         bool mPrecipitation;
         osg::Vec3f mStormDirection;
@@ -355,6 +357,7 @@ namespace MWWorld
         bool updateWeatherRegion(const std::string& playerRegion);
         void updateWeatherTransitions(const float elapsedRealSeconds);
         void forceWeather(const int weatherID);
+        osg::Vec3f calculateStormDirection();
 
         bool inTransition();
         void addWeatherTransition(const int weatherID);
@@ -362,6 +365,7 @@ namespace MWWorld
         void calculateWeatherResult(const float gameHour, const float elapsedSeconds, const bool isPaused);
         void calculateResult(const int weatherID, const float gameHour);
         void calculateTransitionResult(const float factor, const float gameHour);
+        float calculateWindSpeed(int weatherId, float currentSpeed);
     };
 }