[ODE] Re: variable physics rate

[Scott Johnson]

> From: "Vianney Lecroart" <lecroart@noos.fr>
> To: <ode@q12.org>
> Date: Mon, 16 Dec 2002 22:36:50 +0100
> Subject: [ODE] dWorldStep() on non constant frame rate
> 
> Hello,
> 
> I use your great physics engine for a little game I made. I have a
> really strange problem, my loop is like that:
> 
> While (true)
> {
>  newframe = currentime;
>  dt = lasttime-newtime;
>  lastframe = newframe;
>  dWorldStep(dt);
>  sleep(100);
> }
> 
> But the server, sometime slowdown a lot and the dt can be 100ms and some
> time, it near 300ms for one or 2 loops. So we call dWorldStep with 0.3.
> I think it s the good way to do but in all samples you set the
> dWorldStep with a constant value, so it s means that it s frame rate
> depend (0.05). No? It means that if the framerate is 50ms, the physics
> step is 50ms, the rendering is as fast as the realtime, but if the
> framerate is 5ms, the physics will go 10 times faster than the realtime.
> Is is correct?
> 
> I don't really know the good way to manage the problem to manage
> variable framerate.
> 
> Thanks for you help.
> 
> Vianney Lecroart
> 

Vianney,

I am new to ODE but I have done this before in games

dt = 0.0f;
While (true)
{
    newframe = currentTime();
    dt += lasttime - newtime;
    
    while (dt > 1/60.0f )
    {
        TimeStep( 1/60.0f );
        dt -= 1/60.0f;
    }

    // Render, etc
}

I hope that helps.

Scott Johnson
milkboy@austin.rr.com