Time and Physics Steps

Trial includes its own way to deal with physics updates and time passage separate from the rendering. This logic is typically handled by the render-loop class, which is a superclass of display (and thus main). The render-loop keeps a separate thread to perform physics steps and rendering, and to keep the main thread free to handle inputs and OS interactions.

The render-loop will periodically call update on itself in a fixed time step, determined by delta-time, defaulting to 0.01s. This is suitable for physics updates. Despite the fact that the time step (dt) is kept fixed, you should nevertheless not rely on that, and instead only rely on the dt value for all your physics updates. This will make your code more robust and allow the implementation of features such as time slowdown or speedup. The update calls will typically happen in lock-step with real-time. If rendering causes things to slow down beyond real-time, update will be repeatedly called until physics have "caught up", unless the delay is beyond ten seconds, in which case lost time is simply dropped.

The render-loop will also call render on itself as frequently as possible by default. You can force a frame limit using target-framerate (see settings), in which case a fast system will slow itself down automatically to avoid overuse of resources. Another way to restrict frame rate is to enable vsync on the context, though it should be left up to the end user to choose whether to activate vsync or to impose a frame limit.

Typically with main the calls to update are translated to a tick event, which carries the associated information:

• tt A double-float holding the total physics run-time so far.

• dt A single-float holding the period this update should advance physics by.

• fc An integer holding the count of updates so far.

Every update, events are then issued and processed. This will cause the tick to be processed last, after any other pending events, though before any events issued during the event processing itself.