Why do i need to create game loop like those on yt with delta and other stuff if my game loop works

[brittle karma]

Why do i need to create game loop like those on yt with delta and other stuff if my game loop works fine
​​​​java
public void run(){

    while(gameThread != null){

        update();
        repaint();
        try {
            Thread.sleep(9);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }


    }
}

​​​​

[ripe reef]

<@&987246399047479336> please have a look, thanks.

[coral hinge]

I'm not sure what exactly do you mean by delta, but

in your example, your thread will always sleep 9 milliseconds no matter how long the update and repaint took

but if you want to maintain a constant tickrate and fps, you need to only sleep for the amount you actually need

[crimson crystal]

If your player moves 5 pixels each time your loop runs, faster pc's will make the player move faster, and slower pc's will make it move slower

and even if you have a sleep, the time it takes to run update and repaint changes, so you still have that issue

And that's just a simplified explanation

[mental patio]

different computers will run at different speeds based on how fast they update

[brittle karma]

ah okay

can you help me write correct loop

like pseudocode

[pearl wigeon]

https://gafferongames.com/post/fix_your_timestep/

This is THE classic article on game loops

I came back to this a year or two ago when I was testing real time sound generation in Java

[mental patio]

I had to take myself step by step through how game loops worked, I can help you out if you're missing specific concepts

[brittle karma]

i watched some vids on yt but i cant understand what every element doeas

public void run(){

    double drawInterval = 1000000000/FPS;
    double delta = 0;
    long lastTime = System.nanoTime();
    long currentTime;
    long timer = 0;
    int drawCount = 0;



    while (gameThread != null) {

        currentTime = System.nanoTime();

        delta = delta + (currentTime - lastTime) / drawInterval;
        timer = timer + (currentTime - lastTime);
        lastTime = currentTime;

        if(delta >= 1) {

            update();

            repaint();

            delta--;

            drawCount++;
        }
            if(timer >= 1000000000){
                System.out.println("FPS:" + drawCount );
                drawCount = 0;
                timer = 0;
            }
    }
}

this game looop i used

but i have hard time breaking it in my mind

[mental patio]

so this looks really complicated, but it's literally just a loop that updates and renders every 1/FPS

[brittle karma]

okay can you explein this currentTime = System.nanoTime();

        delta = delta + (currentTime - lastTime) / drawInterval;
        timer = timer + (currentTime - lastTime);
        lastTime = currentTime;

also thanks for all help

[mental patio]

So what this does it it gets the current time and subtracts it from the time of the last tick. Then divides it by the drawInterval in nanoseconds, then adds it to delta. Same thing with the timer without the division. Then it gets the current time as the time of last frame so it can be used later.

[mental patio]

I wouldn’t suggest using this loop. It calculates update by tick instead of real time

I would actually suggest using the delta time loop

Delta is the time between ticks so you can calculate what fraction of a second that is and multiply it with your movement to get movement/second instead of movement/tick

So say your game is running at 100 FPS, every tick (if it’s running at a consistent speed which it’s not) is taking 0.01 seconds because 1/FPS is 0.01. Now say you want to move an object across the screen at a rate of 200 pixels per second. You would do velocityX = 200 * delta. This works because 200 * delta (0.01) is 2 meaning the object is moving right at a rate of 2px/tick, and if there’s 100 ticks per second, that’s 200px/second. This works with any FPS, say 60, 200 pixels * delta (0.016667), 3.3333px/tick, 3.3333*60 = 200.