>If it hasn't been x millis, skip it. Render.
>x millis, run it. Render.
>4x millis, run it four times. Render.

This is really fine. This is what I'm doing in my own racing game. There's only a small difference..

In the case you render a frame without running the simulation, it would be really important for the renderer to linearly interpolate the position of the moving object (along its velocity) according to the time passed since the last fixed timestep.

It should look much smoother since vehicles will move every frame. But the calculated position by the renderer is only an approximation it does not really move the body for the simulation. The simulation always move the vehicle with proper physics. If you do not interpolate between frames it will be jerky.

And with the fixed timestep scheme, you almost get instant replay for free if you take some care. : )

[edited by - nosfy on October 24, 2002 8:56:11 AM]

Im using opengl. The game is almost finished and is runs at 86 fps in my computer. what i think i will do is to keep the logic
running at a certain speed. and render the scene multipling the data by a timerfactor (like deyja´s way). This is how i tried to explain, but i think it was not clear.
Thanks for all the answers.