Update m_hardPointWS after a rewind to make sure the current

terrain is computed based on the new (rewound) kart position.

src/karts/kart_rewinder.cpp

@@ -150,6 +150,12 @@ void KartRewinder::restoreState(BareNetworkString *buffer, int count)
     float time_rot = buffer->getFloat();
     // Set timed rotation divides by time_rot
     m_vehicle->setTimedRotation(time_rot, time_rot*buffer->getVec3());
+    // For the raycast to determine the current material under the kart
+    // the m_hardPointWS of the wheels is used. So after a rewind we
+    // must restore the m_hardPointWS to the new values, otherwise they
+    // would still point at the kart position at the previous rewind
+    // (i.e. different terrain --> different slowdown).
+    m_vehicle->updateAllWheelTransformsWS();
 
     // 2) Steering and other controls
     // ------------------------------

src/physics/btKart.cpp

@@ -212,6 +212,20 @@ void btKart::updateWheelTransformsWS(btWheelInfo& wheel,
                                                 wheel.m_wheelAxleCS;
 }   // updateWheelTransformsWS
 
+// ----------------------------------------------------------------------------
+/** Updates all wheel transform informations. This is used just after a rewind
+ *  to update all m_hardPointWS (which is used by stk to determine the terrain
+ *  under the kart).
+ */
+void btKart::updateAllWheelTransformsWS()
+{
+    for (unsigned int i = 0; i < m_wheelInfo.size(); i++)
+    {
+        btWheelInfo &wheel = m_wheelInfo[i];
+        updateWheelTransformsWS(wheel, false, 1.0f);
+    }
+}   // updateAllWheelTransformsWS
+
 // ----------------------------------------------------------------------------
 /**
  */

src/physics/btKart.hpp

@@ -166,6 +166,7 @@ public:
     void               updateWheelTransformsWS(btWheelInfo& wheel,
                                                bool interpolatedTransform=true,
                                                float fraction = 1.0f);
+    void               updateAllWheelTransformsWS();
     void               setAllBrakes(btScalar brake);
     void               updateSuspension(btScalar deltaTime);
     virtual void       updateFriction(btScalar timeStep);