void ComputeForce()
 {
     force = Vector3.zero;
     for (int i = 0; i < behaviours.Count; i++)
     {
         Steering behaviour = behaviours[i];
         if (behaviour.isActiveAndEnabled == false)
         {
             continue;
         }
         force = force + behaviour.GetForce() * behaviour.weighting;
         if (force.magnitude > maxVelocity)
         {
             force = force.normalized * maxVelocity;
             break;
         }
     }
 }