shoot a cannon ball cannot run !!

Dear everyone . I'm doing game kingdomrush in 2D space (demo by cocos2d-x) i've a cannon shoot shoot bullet like a ball move in a parabol path. i see this link : http://answers.unity3d.com/questions/148399/shooting-a-cannonball.html

with this code in unity :

 function BallisticVel(target: Transform, angle: float): Vector3 {
     var dir = target.position - transform.position;  // get target direction
     var h = dir.y;  // get height difference
     dir.y = 0;  // retain only the horizontal direction
     var dist = dir.magnitude ;  // get horizontal distance
     var a = angle * Mathf.Deg2Rad;  // convert angle to radians
     dir.y = dist * Mathf.Tan(a);  // set dir to the elevation angle
     dist += h / Mathf.Tan(a);  // correct for small height differences
     // calculate the velocity magnitude
     var vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 * a));
     return vel * dir.normalized;
 }
 
 var myTarget: Transform;  // drag the target here
 var cannonball: GameObject;  // drag the cannonball prefab here
 var shootAngle: float = 30;  // elevation angle
 
 function Update(){
     if (Input.GetKeyDown("b")){  // press b to shoot
         var ball: GameObject = Instantiate(cannonball, transform.position, Quaternion.identity);
         ball.rigidbody.velocity = BallisticVel(myTarget, shootAngle);
         Destroy(ball, 10);
     }
 }

i convert to cocos2d-x :

 CCPoint Boom :: canculateFiringSolution()
 {
     CCPoint dir = ccpSub(m_target, m_start); //m_start is start postion of bullet
     float h = dir.y;
     dir.y = 0;
     float dist = ccpLength(dir);
     float a = CC_DEGREES_TO_RADIANS(45);
     
     dir.y = (float)dist* tan(a);
     dist = dist + h/tan(a);
 
     float vel = sqrt(dist * 0.01/sin(2*a)); // i must set gravity = 0.01 because if i set -1 same code below. i will run wrong
 
 
     return ccpMult (ccpNormalize(dir),vel);
 }
 
 void Boom::update(float dt)
 {
     m_V = canculateFiringSolution(); //m_v is vector of velocity
     m_bullet->setPosition(CCPoint (m_bullet->getPositionX() + m_V.x, m_bullet->getPositionY() + m_V.y  ));
     
 
 }

i see i convert exactly. but bullet just move linearly, not in parabol path :( Please help me.i've spent many days for this :( Thank you everyone !!! sorry if i post cocos2d-x code in unity3d forum.