void Entity::sync_visible(const b2Body * source, sf::Transformable& target)
{
if( source == NULL )
{
BOOST_THROW_EXCEPTION(Game::Exception());
}
// sync position
{
b2Vec2 b2_position = source->GetPosition();
sf::Vector2f sf_position(
Game::Util::meter_to_pixel(b2_position.x),
Game::Util::meter_to_pixel(b2_position.y)
);
target.setPosition(sf_position);
}
// sync angle
{
target.setRotation(
Game::Util::rad_to_deg(source->GetAngle())
);
}
}
// Simple integrator. Accumulates error as time passes.
void Integrator::Euler(PhysicState& physics,
sf::Transformable& transf,
const HiResDuration& dt)
{
float dtValue = ((float)dt.count()/ONE_SECOND.count());
transf.setPosition(transf.getPosition() + physics.getVelocity() * dtValue);
physics.setVelocity(physics.getVelocity() + (physics.getForce() / physics.getMass()) * dtValue);
}
// More accurate than Euler, but a bit more resource-consuming.
void Integrator::RK4(PhysicState& physics,
sf::Transformable& transf,
const HiResDuration& dt)
{
float dtValue = ((float)dt.count()/ONE_SECOND.count());
Derivative a,b,c,d;
Derivative initial;
a = evaluateRK4(physics, transf, HiResDuration::zero(), initial);
b = evaluateRK4(physics, transf, dt / 2, a);
c = evaluateRK4(physics, transf, dt / 2, b);
d = evaluateRK4(physics, transf, dt, c);
sf::Vector2f dpdt = 1.0f / 6.0f *
( a.dp + 2.0f * (b.dp + c.dp) + d.dp );
sf::Vector2f dvdt = 1.0f / 6.0f *
( a.dv + 2.0f * (b.dv + c.dv) + d.dv );
transf.setPosition(transf.getPosition() + dpdt * dtValue);
physics.setVelocity(physics.getVelocity() + dvdt * dtValue);
}