Quaternion.LookRotation & Vector subtraction

Today, we talk about two very interesting features, vector subtraction and Quaternion.LookRotation on a missile example.

First, we need to find a direction from point A to point B, and we do this by subtracting two Vectors:

Direction = Target position — Missile position

Then, we translate the direction into rotation. In Unity we use Quaternions to handle rotations.

There is a good method that Unity offers named Quaternion.LookRotation(). It takes direction and calculates rotation around Y axis (which is sky by default).

private void AimMissile()
{
    foreach (var missile in missiles)
    {
        // Distance/Direction between missile and target
        var shootingDistance = target.position - missile.transform.position;
        // Quaternion.LookRotation takes shootingDistance Vector3
        // to rotate missile in target's direction
        var missileRotationToTarget = Quaternion.LookRotation(shootingDistance);
        // And finally update missile transform
        missile.transform.rotation = missileRotationToTarget;
    }
}

So, every frame, this method executes a loop throughout missiles array. Every missile individually calculates its own and target coordinates. LookRotation understands the angle at which to rotate each missile. As a result, even if the target shifts to the side, all missiles synchronously adjust their course in flight.