// 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);
}
// Auxiliar function for RK4 integrator
Derivative Integrator::evaluateRK4(const PhysicState& initialPhysics,
const sf::Transformable& initialTransf,
const HiResDuration& dt,
const Derivative& d)
{
float dtValue = ((float)dt.count()/ONE_SECOND.count());
PhysicState physics;
sf::Transformable transf;
transf.setPosition(initialTransf.getPosition() + d.dp * dtValue); // Add the velocity to position
physics.setVelocity(initialPhysics.getVelocity() + d.dv * dtValue); // Add the acceleration to velocity
physics.setForce(initialPhysics.getForce());
physics.setMass(initialPhysics.getMass());
Derivative output;
output.dp = physics.getVelocity();
output.dv = accelerationRK4(physics);
return output;
}
// 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);
}
void Game::Shoot(sf::Transformable& performer)
{
mNewDrawables.push_back(std::make_shared<Shot>(performer.getPosition(), performer.getRotation(), mShotTex));
}
