@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);
}
@Test
public void testMovement() throws Exception {
int iterationCountPerStep = Defaults.ITERATION_COUNT_PER_STEP;
int stepCountPerTimeUnit = 10;
World world = new World(iterationCountPerStep, stepCountPerTimeUnit);
Body body = new Body();
body.setForm(new CircularForm(1.0D));
body.setMass(1.0D);
world.addBody(body);
body.setPosition(0.0D, 0.0D);
body.setVelocity(1.0D, 0.0D);
for (int i = 1; i <= 1000; ++i) {
world.proceed();
Assert.assertEquals(
"Simple movement. Illegal 'x' after step " + i + '.',
0.1D * i,
body.getX(),
world.getEpsilon());
Assert.assertEquals(
"Simple movement. Illegal 'y' after step " + i + '.',
0.0D,
body.getY(),
world.getEpsilon());
}
body.setPosition(0.0D, 0.0D);
body.setVelocity(1.0D, 0.0D);
body.setMovementFrictionFactor(0.1D);
double expectedPositionX = 0.0D;
double expectedVelocityX = 1.0D;
for (int i = 1; i <= 1000; ++i) {
for (int j = 0; j < stepCountPerTimeUnit; ++j) {
expectedPositionX += 0.01D * expectedVelocityX;
expectedVelocityX = max(expectedVelocityX - 0.001D, 0.0D);
}
world.proceed();
Assert.assertEquals(
"Movement with ground friction. Illegal 'x' after step " + i + '.',
expectedPositionX,
body.getX(),
world.getEpsilon());
Assert.assertEquals(
"Movement with ground friction. Illegal 'y' after step " + i + '.',
0.0D,
body.getY(),
world.getEpsilon());
}
body.setPosition(0.0D, 0.0D);
body.setVelocity(1.0D, 0.0D);
body.setMovementFrictionFactor(0.0D);
body.setMovementAirFrictionFactor(0.1D);
expectedPositionX = 0.0D;
expectedVelocityX = 1.0D;
for (int i = 1; i <= 1000; ++i) {
for (int j = 0; j < stepCountPerTimeUnit; ++j) {
expectedPositionX += 0.01D * expectedVelocityX;
expectedVelocityX *= pow(1.0D - 0.1D, 0.01D);
}
world.proceed();
Assert.assertEquals(
"Movement with air friction. Illegal 'x' after step " + i + '.',
expectedPositionX,
body.getX(),
world.getEpsilon());
Assert.assertEquals(
"Movement with air friction. Illegal 'y' after step " + i + '.',
0.0D,
body.getY(),
world.getEpsilon());
}
}
