I´m playing around and trying to make myself an easy platformer using the Box2D physics, before that I was not using it and was using my own physics implementation(just simple movements with timestep). My gameloop architecture now works like this:
while (_isRunning) {
//Processing input events
processInput();
update();
//Rendering stuff
startFPSCap();
render();
delayFPS();
}
The update function is consisting of updating a game world (normal update function without deltatime) - inside this I´m calling a Box2D step function, with desired timestep at 1/60(wanted to have simulation at 60 fps) and then I call my own timestep function to update entity components(so they can be updated also with timestep not just the physics).
void update()
{
_physics->Step(1.0f / 60.0f, 6, 2);
updateEntitiesWithOwnTimestep();
}
However when I tried to run it on slower FPS, the simulation slow downs (even when I capped the FPS to like 200 at the start, so running it at 100 fps is like a slowmotion). I thought that when I set the desired physics simulation for 60 fps it will be no problem when reducing the FPS, but it seems like I´m missing something. Or is there something wrong? I mean, maybe the fact I´m running also my own timestep function.. Thanks for help.
Edit1 - according to Timos answer
Do you mean I should put the delta value I pass to my update function during each step in my own timestep? Like this:
void TimestepManager::update() {
int i = 0;
while ((_totalDeltaTime>0.0f) && (i<MAX_PHYSICS_STEPS)) {
_deltaTime = std::min(_totalDeltaTime, MAX_DELTA_TIME);
//This is std::function - i can define my own behavior via this
_f.exec(_deltaTime);
_physics.Step(_deltaTime, 6, 2);
_totalDeltaTime -= _deltaTime;
i++;
}
}
Or should I pass the total deltaTime? Because I thought that I should keep this unchanged because I don´t want to tie the simulation with the FPS.
