Usually a constant time step is used, and you throttle the rate at which you run physics ticks to make that match wall clock time. It’s common for game physics

Usually a constant time step is used, and you throttle the rate at which you run physics ticks to make that match wall clock time. It’s common for game physics engines to also run iterative integrators for a fixed number of steps per tick instead of to convergence, which reduces variation in work per tick. If the system can’t keep up, you start dropping physics frames. You keep animation smooth by decoupling it from physics; the output of your physics engine will generally include at least linear and angular velocities you can use for interpolation. This kind of thing is necessary anyway if you’re running your physics simulation on a server and have to communicate to the renderer over the network.