Fixed time-step

In some cases, the code for time management that we've written doesn't really apply correctly. Let's say we only want to call certain methods at a fixed rate of 60 times per second. It could be a physics system that requires updating only a certain amount of times, or it can be useful if the game is grid-based. Whatever the case is, when an update rate is really important, a fixed time-step is your friend. Unlike the variable time-step, where the next update and draw happens as soon as the previous one is done, the fixed time-step approach will ensure that certain game logic is only happening at a provided rate. It's fairly simple to implement a fixed time-step. First, we must make sure that instead of overwriting the elapsed time value of the previous iteration, we add to it like so:

void Game::RestartClock(){
    m_elapsed += m_clock.restart();
}

The basic expression for calculating the amount of time for an individual update throughout a 1 second interval is illustrated...