Make sure sky particles always fall vertically

src/karts/controller/local_player_controller.cpp

@@ -54,6 +54,8 @@
 #include "input/gamepad_device.hpp"
 #include "input/sdl_controller.hpp"
 
+#include "LinearMath/btTransform.h"
+
 /** The constructor for a loca player kart, i.e. a player that is playing
  *  on this machine (non-local player would be network clients).
  *  \param kart_name Name of the kart.
@@ -263,25 +265,23 @@ void LocalPlayerController::update(int ticks)
     {
         if (m_controls->getLookBack() || (UserConfigParams::m_reverse_look_threshold > 0 &&
             m_kart->getSpeed() < -UserConfigParams::m_reverse_look_threshold))
-        {
             camera->setMode(Camera::CM_REVERSE);
-            if (m_sky_particles_emitter)
-            {
-                m_sky_particles_emitter->setPosition(Vec3(0, 30, -100));
-                m_sky_particles_emitter->setRotation(Vec3(0, 180, 0));
-            }
-        }
         else
         {
             if (camera->getMode() == Camera::CM_REVERSE)
-            {
                 camera->setMode(Camera::CM_NORMAL);
-                if (m_sky_particles_emitter)
+        }
-                {
+        if (m_sky_particles_emitter)
-                    m_sky_particles_emitter->setPosition(Vec3(0, 30, 100));
+        {
-                    m_sky_particles_emitter->setRotation(Vec3(0, 0, 0));
+            // Need to set it every frame to account for heading changes
-                }
+            btTransform local_trans(btQuaternion(Vec3(0, 1, 0), 0),
+                Vec3(0, 30, 100));
+            if (camera->getMode() == Camera::CM_REVERSE)
+            {
+                local_trans = btTransform (btQuaternion(Vec3(0, 1, 0),
+                    180.0 * DEGREE_TO_RAD), Vec3(0, 30, -100));
             }
+            setParticleEmitterPosition(local_trans);
         }
     }
 
@@ -300,6 +300,22 @@ void LocalPlayerController::update(int ticks)
     }
 }   // update
 
+//-----------------------------------------------------------------------------
+void LocalPlayerController::setParticleEmitterPosition(const btTransform& t)
+{
+#ifndef SERVER_ONLY
+    btTransform world_trans(btQuaternion(Vec3(0, 1, 0), m_kart->getHeading()),
+        m_kart->getXYZ());
+    world_trans *= t;
+    btTransform inv_kart = m_kart->getTrans().inverse();
+    inv_kart *= world_trans;
+    m_sky_particles_emitter->setPosition(Vec3(inv_kart.getOrigin()));
+    Vec3 rotation;
+    rotation.setHPR(inv_kart.getRotation());
+    m_sky_particles_emitter->setRotation(rotation.toIrrHPR());
+#endif
+}   // setParticleEmitterPosition
+
 //-----------------------------------------------------------------------------
 /** Displays a penalty warning for player controlled karts. Called from
  *  LocalPlayerKart::update() if necessary.

src/karts/controller/local_player_controller.hpp

@@ -28,6 +28,7 @@ class AbstractKart;
 class ParticleEmitter;
 class SFXBase;
 class SFXBuffer;
+class btTransform;
 
 /** PlayerKart manages control events from the player and moves
   * them to the Kart
@@ -68,6 +69,7 @@ private:
     void         nitroNotFullSound();
 
     void doCrashHaptics();
+    void setParticleEmitterPosition(const btTransform& t);
 
 public:
                  LocalPlayerController(AbstractKart *kart,