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* Copyright (c) 2013, Daniel Murphy
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******************************************************************************/
/**
* Created at 5:18:10 AM Jan 14, 2011
*/
package org.jbox2d.testbed.tests;
import org.jbox2d.callbacks.ContactImpulse;
import org.jbox2d.collision.shapes.EdgeShape;
import org.jbox2d.collision.shapes.PolygonShape;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.BodyType;
import org.jbox2d.dynamics.Fixture;
import org.jbox2d.dynamics.contacts.Contact;
import org.jbox2d.testbed.framework.TestbedSettings;
import org.jbox2d.testbed.framework.TestbedTest;
/**
* @author Daniel Murphy
*/
public class Breakable extends TestbedTest {
Body m_body1;
Vec2 m_velocity = new Vec2();
float m_angularVelocity;
PolygonShape m_shape1;
PolygonShape m_shape2;
Fixture m_piece1;
Fixture m_piece2;
boolean m_broke;
boolean m_break;
@Override
public void initTest(boolean argDeserialized) {
// Ground body
{
BodyDef bd = new BodyDef();
Body ground = getWorld().createBody(bd);
EdgeShape shape = new EdgeShape();
shape.set(new Vec2(-40.0f, 0.0f), new Vec2(40.0f, 0.0f));
ground.createFixture(shape, 0.0f);
}
// Breakable dynamic body
{
BodyDef bd = new BodyDef();
bd.type = BodyType.DYNAMIC;
bd.position.set(0.0f, 40.0f);
bd.angle = 0.25f * MathUtils.PI;
m_body1 = getWorld().createBody(bd);
m_shape1 = new PolygonShape();
m_shape1.setAsBox(0.5f, 0.5f, new Vec2(-0.5f, 0.0f), 0.0f);
m_piece1 = m_body1.createFixture(m_shape1, 1.0f);
m_shape2 = new PolygonShape();
m_shape2.setAsBox(0.5f, 0.5f, new Vec2(0.5f, 0.0f), 0.0f);
m_piece2 = m_body1.createFixture(m_shape2, 1.0f);
}
m_break = false;
m_broke = false;
}
@Override
public void postSolve(Contact contact, ContactImpulse impulse) {
if (m_broke) {
// The body already broke.
return;
}
// Should the body break?
int count = contact.getManifold().pointCount;
float maxImpulse = 0.0f;
for (int i = 0; i < count; ++i) {
maxImpulse = MathUtils.max(maxImpulse, impulse.normalImpulses[i]);
}
if (maxImpulse > 40.0f) {
// Flag the body for breaking.
m_break = true;
}
}
void Break() {
// Create two bodies from one.
Body body1 = m_piece1.getBody();
Vec2 center = body1.getWorldCenter();
body1.destroyFixture(m_piece2);
m_piece2 = null;
BodyDef bd = new BodyDef();
bd.type = BodyType.DYNAMIC;
bd.position = body1.getPosition();
bd.angle = body1.getAngle();
Body body2 = getWorld().createBody(bd);
m_piece2 = body2.createFixture(m_shape2, 1.0f);
// Compute consistent velocities for new bodies based on
// cached velocity.
Vec2 center1 = body1.getWorldCenter();
Vec2 center2 = body2.getWorldCenter();
Vec2 velocity1 = m_velocity.add(Vec2.cross(m_angularVelocity, center1.sub(center)));
Vec2 velocity2 = m_velocity.add(Vec2.cross(m_angularVelocity, center2.sub(center)));
body1.setAngularVelocity(m_angularVelocity);
body1.setLinearVelocity(velocity1);
body2.setAngularVelocity(m_angularVelocity);
body2.setLinearVelocity(velocity2);
}
@Override
public void step(TestbedSettings settings) {
super.step(settings);
if (m_break) {
Break();
m_broke = true;
m_break = false;
}
// Cache velocities to improve movement on breakage.
if (m_broke == false) {
m_velocity.set(m_body1.getLinearVelocity());
m_angularVelocity = m_body1.getAngularVelocity();
}
}
@Override
public String getTestName() {
return "Breakable";
}
}