gistfile1.cpp

void MovableObject::update()
{
    Time newTime = Clock::now();
    double frameTime = toSeconds(newTime-currentTime).count();
    currentTime = Clock::now();

    accumulator += frameTime;

    while (accumulator >= dt)
    {
        prevState = currState;

        Vector2d d1 = currState.vel;
        Vector2d d2 = currState.vel + currState.acc * dt * 0.5;
        Vector2d d3 = currState.vel + currState.acc * dt * 0.5;
        Vector2d d4 = currState.vel + currState.acc * dt;

        Vector2d dpdt = (1.0 / 6.0) * (d1 + (d2 + d3) * 2.0 + d4);

        currState.pos = currState.pos + dpdt * dt;
        currState.vel = currState.vel + currState.acc * dt;

        accumulator -= dt;
    }
    const double alpha = accumulator / dt;
    rect.setPosition(sf::Vector2f(currState.pos * alpha + prevState.pos * (1.0 - alpha)));
}