CODEWITHSUNDEEP
javaandroidlibgdx
Crigges
Crigges

Reputation: 1243

Moving an object unaffected by FPS

Hello I am currently trying to move objects in my libgdx android application. The main issue is that i can't move my objects unaffected by the fps. Up to now i was using the delta time like this:

public void move(float delta){
    this.setX(this.getX() + this.speed.x * delta); //moving just along x axis to keep it simple
    this.speed.x += 1 * delta //some acceleration;
}

The move method is called on each frame. Imagine I have two devices, one with 1fps and one with 2fps, and now we move a object for 1 second with a start speed of zero. The object wouldn't have moved on the first device while it would have on the second one. To sum up if the fps is increased the object moves slightly faster.

Up to now this little differnce was no problem but in this case it is important that the object moves 100% synchronous, because i want to measure the time the objects needs to reach some point.

So what is the right way to go here?

Upvotes: 0

Views: 231

Answers (2)

Crigges
Crigges

Reputation: 1243

Thanks to m.antkowicz provided informations i could do some better research and found some interesting artices. According to my current knowlege it is pretty hard move objects with dynamic accelleration based on the deltatime. The right way to go is to use fixed time stamps.

Upvotes: 0

m.antkowicz
m.antkowicz

Reputation: 13571

Actually... the way you are moving your objects when multiplying it by delta makes it FPS independent already :) Let see below graphic to understand it better:

enter image description here

open the picture in full size!

Atlhough you are adding some value to x twice per second when having 2FPS the value is twice smaller than when having 1FPS what means that in the every integer point of time the x of the object will be the same.

The situation you are afraid of would be true if you wouldn't multiply it by delta - then every second you would add the same value twice when having 2FPS than when having 1FPS - it means that after one second the object would be twice far more when having 2FPS than when having 1FPS.

Only thing affect by the FPS is rendering smoothness - but if you are refreshing the screen twice times more it is obvious that it will be more smooth.

By the way - if you are using Scene2D and looking for some other ways to move object look at Actions especially MoveToAction. Take a look at this tutorial to get some information.

Upvotes: 2

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