Avoid setting gravity in btKart

src/karts/kart.cpp

@@ -1370,6 +1370,13 @@ void Kart::update(float dt)
     const Material* material=m_terrain_info->getMaterial();
     if (!material)   // kart falling off the track
     {
+        if (!m_flying)
+        {
+            float g = World::getWorld()->getTrack()->getGravity();
+            Vec3 gravity(0, -g, 0);
+            btRigidBody *body = getVehicle()->getRigidBody();
+            body->setGravity(gravity);
+        }
         // let kart fall a bit before rescuing
         const Vec3 *min, *max;
         World::getWorld()->getTrack()->getAABB(&min, &max);
@@ -1380,6 +1387,19 @@ void Kart::update(float dt)
     }
     else
     {
+        if (!m_flying)
+        {
+            float g = World::getWorld()->getTrack()->getGravity();
+            Vec3 gravity(0.0f, -g, 0.0f);
+            btRigidBody *body = getVehicle()->getRigidBody();
+            // If the material should overwrite the gravity,
+            if (material->hasGravity())
+            {
+                Vec3 normal = m_terrain_info->getNormal();
+                gravity = normal * -g;
+            }
+            body->setGravity(gravity);
+        }   // if !flying
         handleMaterialSFX(material);
         if     (material->isDriveReset() && isOnGround())
             new RescueAnimation(this);

src/modes/world.cpp

@@ -27,6 +27,7 @@
 #include "config/user_config.hpp"
 #include "graphics/camera.hpp"
 #include "graphics/irr_driver.hpp"
+#include "graphics/material.hpp"
 #include "graphics/render_info.hpp"
 #include "io/file_manager.hpp"
 #include "input/device_manager.hpp"
@@ -695,6 +696,13 @@ void World::resetAllKarts()
 
     // Do a longer initial simulation, which should be long enough for all
     // karts to be firmly on ground.
+    float g = World::getWorld()->getTrack()->getGravity();
+    for (KartList::iterator i = m_karts.begin(); i != m_karts.end(); i++)
+    {
+        if ((*i)->isGhostKart()) continue;
+        (*i)->getBody()->setGravity((*i)->getMaterial()->hasGravity() ?
+            (*i)->getNormal() * -g : Vec3(0, -g, 0));
+    }
     for(int i=0; i<60; i++) m_physics->update(1.f/60.f);
 
     for ( KartList::iterator i=m_karts.begin(); i!=m_karts.end(); i++)

src/physics/btKart.cpp

@@ -25,7 +25,6 @@
 #include "graphics/material.hpp"
 #include "karts/kart.hpp"
 #include "modes/world.hpp"
-#include "physics/physics.hpp"
 #include "physics/triangle_mesh.hpp"
 #include "tracks/terrain_info.hpp"
 #include "tracks/track.hpp"
@@ -376,18 +375,6 @@ void btKart::updateAllWheelPositions()
 // ----------------------------------------------------------------------------
 void btKart::updateVehicle( btScalar step )
 {
-    bool new_g = m_kart->getMaterial() && m_kart->getMaterial()->hasGravity();
-    if (new_g && !m_kart->isFlying())
-    {
-        getRigidBody()->setGravity(m_kart->getNormal() * World::getWorld()
-            ->getPhysics()->getPhysicsWorld()->getGravity().y());
-    }
-    else if (!m_kart->isFlying())
-    {
-        getRigidBody()->setGravity(World::getWorld()
-            ->getPhysics()->getPhysicsWorld()->getGravity());
-    }
-
     updateAllWheelPositions();
 
     const btTransform& chassisTrans = getChassisWorldTransform();
@@ -459,7 +446,9 @@ void btKart::updateVehicle( btScalar step )
     if(m_num_wheels_on_ground==0)
     {
         btVector3 kart_up    = getChassisWorldTransform().getBasis().getColumn(1);
-        btVector3 terrain_up = new_g ? m_kart->getNormal() : Vec3(0, 1, 0);
+        btVector3 terrain_up =
+            m_kart->getMaterial() && m_kart->getMaterial()->hasGravity() ?
+            m_kart->getNormal() : Vec3(0, 1, 0);
         // Length of axis depends on the angle - i.e. the further awat
         // the kart is from being upright, the larger the applied impulse
         // will be, resulting in fast changes when the kart is on its