/**
* Step the simulation. Currently anything other than 1/60f as a step leads to unpredictable
* results - hence the default step fixes us to this step
*
* @param dt The amount of time to step
*/
public void step(float dt) {
for (int i = 0; i < bodies.size(); ++i) {
for (int j = 0; j < sources.size(); j++) {
((ForceSource) sources.get(j)).apply(bodies.get(i), dt);
}
}
BodyList bodies = getActiveBodies();
JointList joints = getActiveJoints();
float invDT = dt > 0.0f ? 1.0f / dt : 0.0f;
if (restingBodyDetection) {
for (int i = 0; i < bodies.size(); ++i) {
Body b = bodies.get(i);
b.startFrame();
}
for (int i = 0; i < joints.size(); ++i) {
Joint j = joints.get(i);
j.getBody1().setIsResting(false);
j.getBody2().setIsResting(false);
}
}
broadPhase(dt);
for (int i = 0; i < bodies.size(); ++i) {
Body b = bodies.get(i);
if (b.getInvMass() == 0.0f) {
continue;
}
if (b.isResting() && restingBodyDetection) {
continue;
}
Vector2f temp = new Vector2f(b.getForce());
temp.scale(b.getInvMass());
if (b.getGravityEffected()) {
temp.add(gravity);
}
temp.scale(dt);
b.adjustVelocity(temp);
Vector2f damping = new Vector2f(b.getVelocity());
damping.scale(-b.getDamping() * b.getInvMass());
b.adjustVelocity(damping);
b.adjustAngularVelocity(dt * b.getInvI() * b.getTorque());
b.adjustAngularVelocity(-b.getAngularVelocity() * b.getInvI() * b.getRotDamping());
}
for (int i = 0; i < arbiters.size(); i++) {
Arbiter arb = arbiters.get(i);
if (!restingBodyDetection || !arb.hasRestingPair()) {
arb.preStep(invDT, dt, damping);
}
}
for (int i = 0; i < joints.size(); ++i) {
Joint j = joints.get(i);
j.preStep(invDT);
}
for (int i = 0; i < iterations; ++i) {
for (int k = 0; k < arbiters.size(); k++) {
Arbiter arb = arbiters.get(k);
if (!restingBodyDetection || !arb.hasRestingPair()) {
arb.applyImpulse();
} else {
arb.getBody1().collided(arb.getBody2());
arb.getBody2().collided(arb.getBody1());
}
}
for (int k = 0; k < joints.size(); ++k) {
Joint j = joints.get(k);
j.applyImpulse();
}
}
for (int i = 0; i < bodies.size(); ++i) {
Body b = bodies.get(i);
if (b.getInvMass() == 0.0f) {
continue;
}
if (restingBodyDetection) {
if (b.isResting()) {
continue;
}
}
b.adjustPosition(b.getVelocity(), dt);
b.adjustPosition(b.getBiasedVelocity(), dt);
b.adjustRotation(dt * b.getAngularVelocity());
b.adjustRotation(dt * b.getBiasedAngularVelocity());
b.resetBias();
b.setForce(0, 0);
b.setTorque(0);
}
if (restingBodyDetection) {
for (int i = 0; i < bodies.size(); ++i) {
Body b = bodies.get(i);
b.endFrame();
}
}
cleanUpArbiters();
}
/**
* Set the gravity applied in the world
*
* @param x The x component of the gravity factor
* @param y The y component of the gravity factor
*/
public void setGravity(float x, float y) {
gravity.x = x;
gravity.y = y;
}