Quick tip

RaycastHit hit;
rayDirection = playerTransform.position - transform.position;

if ((Vector3.Angle (rayDirection, transform.forward)) < fieldOfView)
{
    if (Physics.Raycast (transform.position, rayDirection, out hit, ViewDistance))
    {
        var collider = hit.collider;
       //....
    }
}


// testowanie
void OnDrawGizmos() {
 if (playerTransform == null) {
 return;
 }

 Debug.DrawLine (transform.position, playerTransform .position, Color.red);

 Vector3 frontRayPoint = transform.position + (transform.forward * ViewDistance);

 Vector3 leftRayPoint = frontRayPoint;
 leftRayPoint.x += fieldOfView * 0.5f;

 Vector3 rightRayPoint = frontRayPoint;
 rightRayPoint.x -= fieldOfView * 0.5f;

 Debug.DrawLine (transform.position, frontRayPoint, Color.green);
 Debug.DrawLine (transform.position, leftRayPoint, Color.green);
 Debug.DrawLine (transform.position, rightRayPoint, Color.green);
}