Try to reduce likelihood of karts 'driving' over a fence (by

collisions that pushes them with away with an upwards component
in the impulse vector).


git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@12528 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/karts/kart.cpp

@@ -1600,7 +1600,13 @@ void Kart::crashed(const Material *m, const Vec3 &normal)
                              ==KartProperties::IMPULSE_NORMAL &&
         m_vehicle->getCentralImpulseTime()<=0                     )
     {
-        Vec3 impulse = normal;
+        // Restrict impule to plane defined by gravity (i.e. X/Z plane).
+        // This avoids the problem that karts can be pushed up, e.g. above
+        // a fence.
+        btVector3 gravity = m_body->getGravity();
+        gravity.normalize();
+        // Cast necessary since otherwise to operator- (vec3/btvector) exists
+        Vec3 impulse =  (btVector3)normal - gravity* btDot(normal, gravity);
         if(impulse.getX() || impulse.getZ())
             impulse.normalize();
         else