Проблемы с физикой 2д машины из статьи "Физика автомобиля для игр"

#define  DRAG    5.0         /* factor for air resistance (drag)   */
#define  RESISTANCE  30.0      /* factor for rolling resistance */
#define CA_R    -5.20      /* cornering stiffness */
#define CA_F    -5.0      /* cornering stiffness */
#define MAX_GRIP  2.0        /* maximum (normalised) friction force, =diameter of friction circle */


void Update()
{
  sn = Math.sin(car_angle);
  cs = Math.cos(car_angle);

  // SAE convention: x is to the front of the car, y is to the right, z is down
  
  // transform velocity in world reference frame to velocity in car reference frame
  velocity_x =  cs * car_velocity_wc_y + sn * car_velocity_wc_x;
  velocity_y = -sn * car_velocity_wc_y + cs * car_velocity_wc_x;

// Lateral force on wheels
//  
  // Resulting velocity of the wheels as result of the yaw rate of the car body
  // v = yawrate * r where r is distance of wheel to CG (approx_ half wheel base)
  // yawrate (ang_velocity) must be in rad/s
  //
  yawspeed = car_cartype_wheelbase * 0.5 * car_angularvelocity;  

  if( velocity_x == 0 )    // TODO: fix singularity
    rot_angle = 0;
  else
    rot_angle = Math.atan2( yawspeed, velocity_x);

  // Calculate the side slip angle of the car (a_k_a_ beta)
  if( velocity_x == 0 )    // TODO: fix singularity
    sideslip = 0;
  else
    sideslip = Math.atan2( velocity_y, velocity_x);    

  // Calculate slip angles for front and rear wheels (a_k_a_ alpha)
  slipanglefront = sideslip + rot_angle - car_steerangle;
  slipanglerear  = sideslip - rot_angle;

  // weight per axle = half car mass times 1G (=9_8m/s^2) 
  weight = car_cartype_mass * 9.8 * 0.5;  
  
  // lateral force on front wheels = (Ca * slip angle) capped to friction circle * load
  flatf_x = 0;
  flatf_y = CA_F * slipanglefront;
  flatf_y = Math.min(MAX_GRIP, flatf_y);
  flatf_y = Math.max(-MAX_GRIP, flatf_y);
  flatf_y *= weight;
  if(front_slip)
    flatf_y *= 0.5;

  // lateral force on rear wheels
  flatr_x = 0;
  flatr_y = CA_R * slipanglerear;
  flatr_y = Math.min(MAX_GRIP, flatr_y);
  flatr_y = Math.max(-MAX_GRIP, flatr_y);
  flatr_y *= weight;
  if(rear_slip)
    flatr_y *= 0.5;

  // longtitudinal force on rear wheels - very simple traction model

  ftraction_x = 100*(car_throttle - car_brake*velocity_x);  
  ftraction_y = 0;
  if(rear_slip)
    ftraction_x *= 0.5;

// Forces and tor2 on body
  
  // drag and rolling resistance
  resistance_x = -( RESISTANCE*velocity_x + DRAG*velocity_x*Math.abs(velocity_x) );
  resistance_y = -( RESISTANCE*velocity_y + DRAG*velocity_y*Math.abs(velocity_y) );

  // sum forces
  force_x = ftraction_x + Math.sin(car_steerangle) * flatf_x + flatr_x + resistance_x;
  force_y = ftraction_y + Math.cos(car_steerangle) * flatf_y + flatr_y + resistance_y;  

  // tor2 on body from lateral forces
  tor2 = car_cartype_b * flatf_y - car_cartype_c * flatr_y;

// Acceleration
  
  // Newton F = m_a, therefore a = F/m
  acceleration_x = force_x/car_cartype_mass;
  acceleration_y = force_y/car_cartype_mass;
  
  angular_acceleration = tor2 / car_cartype_inertia;

// Velocity and position

  // transform acceleration from car reference frame to world reference frame
  acceleration_wc_x =  cs * acceleration_y + sn * acceleration_x;
  acceleration_wc_y = -sn * acceleration_y + cs * acceleration_x;

  // velocity is integrated acceleration
  //
  car_velocity_wc_x += delta_t * acceleration_wc_x;
  car_velocity_wc_y += delta_t * acceleration_wc_y;

  // position is integrated velocity
  //
  
    
  car_position_wc_x += delta_t * car_velocity_wc_x;
  car_position_wc_y += delta_t * car_velocity_wc_y;
  


// Angular velocity and heading

  // integrate angular acceleration to get angular velocity
  //
  car_angularvelocity += delta_t * angular_acceleration;

  // integrate angular velocity to get angular orientation
  //
  car_angle += delta_t * car_angularvelocity ;
    
    
    
    
    

}