void AccelerateAction::apply(const DrawablePtr& target, const DateTime& thisFrameStartTime, const TimeDuration& deltaTime)
{
// basic physics
// v = a t
// d = v t
// d = 1/2 a t^2
// delta_d = 1/2 a t^2 - 1/2 a (t-delta_t)^2 : 6 *, 2 -
// alternate forms (thanks to wolfram alpha)
// delta_d = -1/2 a delta_t (delta_t - 2 t) : 4 *, 1 - (using this one)
// delta_d = a delta_t t - (a delta_t^2)/2 : 4 *, 1 /, 1 -
// delta_d = 1/2 a delta_t (2 t - delta_t) : 4 *, 1 -
elapsedTime += deltaTime;
double delta_t = deltaTime.realSeconds();
double t = elapsedTime.realSeconds();
Point position = target->position();
currentSpeed = t * yPixelsPerSecondSquared;
if( (useMaxSpeed && (currentSpeed <= maxSpd)) || (!useMaxSpeed))
{
position.y() += -.5 * yPixelsPerSecondSquared * delta_t * (delta_t - 2 * t);
}
else
{
position.y() += maxSpd *delta_t;
}
position.x() += -.5 * xPixelsPerSecondSquared * delta_t * (delta_t - 2 * t);
target->setPosition(position);
}
