There's another another way to do this, which I have used successfully for years - The fixed time step simulation is the ground truth "goal", and the "render s

There's another another way to do this, which I have used successfully for years - The fixed time step simulation is the ground truth "goal", and the "render simulation" is "pulled" towards the goal using an exponential moving average interpolation. I find that moving the render simulation 90% of the way to the goal every 80 milliseconds feels good for UI interactions. That means that the rendered version is 99% of the way to the goal after 160 msec, 99.9% after 240 msec, etcetera. This also has the nice property that the render sim is always smooth regardless of tick rate and it never overshoots the goal sim.