Fix explosion animation on upside down area

src/karts/explosion_animation.cpp

@@ -77,6 +77,7 @@ ExplosionAnimation::ExplosionAnimation(AbstractKart *kart,
  {
     m_xyz = m_kart->getXYZ();
     m_orig_xyz = m_xyz;
+    m_normal = m_kart->getNormal();
     m_kart->playCustomSFX(SFXManager::CUSTOM_EXPLODE);
     m_timer = m_kart->getKartProperties()->getExplosionDuration();
 
@@ -141,11 +142,10 @@ ExplosionAnimation::~ExplosionAnimation()
 void ExplosionAnimation::update(float dt)
 {
     m_velocity -= dt*World::getWorld()->getTrack()->getGravity();
-    Vec3 normal = -1.0f*m_kart->getBody()->getGravity().normalized();
-    m_xyz = Vec3(m_xyz + dt*m_velocity*normal);
+    m_xyz = m_xyz + dt*m_velocity*m_normal;
 
     // Make sure the kart does not end up under the track
-    if ((m_xyz - m_orig_xyz).dot(normal)<0)
+    if ((m_xyz - m_orig_xyz).dot(m_normal)<0)
     {
         m_xyz = m_orig_xyz;
         // This will trigger the end of the animations

src/karts/explosion_animation.hpp

@@ -37,14 +37,18 @@
 class ExplosionAnimation: public AbstractKartAnimation
 {
 protected:
-    /** The coordinates where the kart was hit originally. */
+    /** The coordinates where the kart was hit originally, it will be increased
+     *  later. */
     Vec3 m_xyz;
 
-    /** The original Y coordinate. The kart needs to be restored accurately
+    /** The original coordinates. The kart needs to be restored accurately
      *  otherwise due to floating point errors, time step size variations,
      *  a kart can be restarted under the track. */
     Vec3 m_orig_xyz;
 
+    /** The normal of kart when it started to explode. */
+    Vec3 m_normal;
+
     /** The kart's current rotation. */
     Vec3 m_curr_rotation;