@Test
public void testMomentumTransferFactor() throws Exception {
int iterationCountPerStep = Defaults.ITERATION_COUNT_PER_STEP;
int stepCountPerTimeUnit = 1;
double originalVelocityModule = 0.1D;
World world = new World(iterationCountPerStep, stepCountPerTimeUnit);
Body bodyA = new Body();
bodyA.setForm(new CircularForm(1.0D));
bodyA.setMass(1.0D);
bodyA.setMomentumTransferFactor(0.5D);
world.addBody(bodyA);
bodyA.setPosition(0.0D, 0.0D);
bodyA.setVelocity(originalVelocityModule, 0.0D);
Body bodyB = new Body();
bodyB.setForm(new CircularForm(1.0D));
bodyB.setMass(1.0D);
bodyB.setMomentumTransferFactor(0.5D);
world.addBody(bodyB);
bodyB.setPosition(3.0D, 0.0D);
bodyB.setVelocity(-originalVelocityModule, 0.0D);
for (int i = 1; i <= 10; ++i) {
world.proceed();
}
Assert.assertEquals(
"Inelastic collision test. Illegal speed module "
+ bodyA.getVelocity().getLength()
+ " of body A.",
originalVelocityModule
* bodyA.getMomentumTransferFactor()
* bodyB.getMomentumTransferFactor(),
bodyA.getVelocity().getLength(),
Defaults.EPSILON);
Assert.assertEquals(
"Inelastic collision test. Illegal speed module "
+ bodyB.getVelocity().getLength()
+ " of body B.",
originalVelocityModule
* bodyA.getMomentumTransferFactor()
* bodyB.getMomentumTransferFactor(),
bodyB.getVelocity().getLength(),
Defaults.EPSILON);
}
/** Resets the widget to start state. */
public void resetWidget() {
// Reset has been made, so we CAN activate this later.
reset = true;
// Make inactive
active = false;
// Not collided.
collided = false;
bounces = 0;
currentDirection = direction;
image = frames.get(0);
body.setEnabled(false);
// Move to initial position.
body.set(shape, MASS);
body.setPosition(position.x + WIDTH / 2, position.y + HEIGHT / 2);
// Make sure the gameplay didn't mess with any initial properties.
body.setCanRest(true);
body.setDamping(0.0f);
body.setFriction(0.01f);
body.setGravityEffected(false);
body.setIsResting(true);
body.setMoveable(true);
body.setRestitution(1.5f);
body.setRotatable(true);
body.setRotation(0.0f);
body.setRotDamping(0.0f);
body.setMaxVelocity(50f, 50f);
body.setForce(-body.getForce().getX(), -body.getForce().getY());
if (currentDirection == Direction.WEST) {
body.setForce(-MOVEMENT_SPEED, 0);
} else if (currentDirection == Direction.EAST) {
body.setForce(MOVEMENT_SPEED, 0);
}
if (currentDirection == Direction.NORTH) {
body.setForce(0, -MOVEMENT_SPEED);
} else if (currentDirection == Direction.SOUTH) {
body.setForce(0, MOVEMENT_SPEED);
}
body.adjustVelocity(new Vector2f(-body.getVelocity().getX(), -body.getVelocity().getY()));
body.adjustAngularVelocity(-body.getAngularVelocity());
}
/**
* 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();
}
