Greatly varying projectile speed on different devices

Unity Engine
1

Hello again everybody,
so I am working on a FPS tower defense game and of course there are bullets to move. I do that using the following code in a script attached to the bullet:

        GetComponent<Rigidbody>().velocity = direction * Time.deltaTime * bulletSpeed;

with a bulletspeed of 10k which I set up on a low fps laptop and the speed seemed just fine.
Back on my main PC with way higher fps the bullet is extremely slow.
Now I am still pretty new to Unity and C# scripting in general but in pretty much every tutorial I watched they said using Time.deltaTime would fix that exact problem. Is there another way to fix it? My limited knowledge doesn’t allow me to come up with a solution myself.

Thanks in advance :wink:

2

You shouldn’t set velocity, you should change position. On your better PC fps is higher, i.e Time.deltaTime is lower, of course result velocity will be very low. It should be:

private void Update()
{
    rigidbody.position += direction * (Time.deltaTime * speed);
}

For more consistency you can use FixedUpdate, since even with Time.deltaTime it won’t be 100% accurate, to make everything smooth you can change projectile rigidbody to interpolation.

private void Awake()
{
   rigidbody.interpolation = RigidbodyInterpolation.Interpolate
}

private void FixedUpdate()
{
    //deltaTime will be automatically fixedDeltaTime
    rigidbody.position += direction * (Time.deltaTime * speed);
}
3

oh wait did I just mix up position and velocity? Is velocity independent from fps and setting velocity without Time.deltaTime would archieve the same speed on different devices? Because I really liked just setting the velocity once instead of moving the bullet each frame

4

If projectile isn’t stopped by anything and have constant speed, then you can simply set velocity one time in Awake/Start without Time.deltaTime, and yes, this will work.

5

thanks a lot :slight_smile: