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The testbed for JBox2D, a 2d java physics engine, ported from the C++ Box2d engine.
/*******************************************************************************
* Copyright (c) 2013, Daniel Murphy
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
******************************************************************************/
/**
* Created at 7:50:04 AM Jan 20, 2011
*/
package org.jbox2d.testbed.tests;
import org.jbox2d.collision.shapes.PolygonShape;
import org.jbox2d.common.Mat22;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Transform;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.BodyType;
import org.jbox2d.dynamics.FixtureDef;
import org.jbox2d.dynamics.joints.FrictionJointDef;
import org.jbox2d.testbed.framework.TestbedSettings;
import org.jbox2d.testbed.framework.TestbedTest;
/**
* @author Daniel Murphy
*/
public class ApplyForce extends TestbedTest {
private static final long BODY_TAG = 1;
Body m_body;
/**
* @see org.jbox2d.testbed.framework.TestbedTest#initTest(boolean)
*/
@Override
public void initTest(boolean argDeserialized) {
if(argDeserialized){
return;
}
getWorld().setGravity(new Vec2(0.0f, 0.0f));
final float k_restitution = 0.4f;
Body ground;
{
BodyDef bd = new BodyDef();
bd.position.set(0.0f, 20.0f);
ground = getWorld().createBody(bd);
PolygonShape shape = new PolygonShape();
FixtureDef sd = new FixtureDef();
sd.shape = shape;
sd.density = 0.0f;
sd.restitution = k_restitution;
// Left vertical
shape.setAsEdge(new Vec2(-20.0f, -20.0f), new Vec2(-20.0f, 20.0f));
ground.createFixture(sd);
// Right vertical
shape.setAsEdge(new Vec2(20.0f, -20.0f), new Vec2(20.0f, 20.0f));
ground.createFixture(sd);
// Top horizontal
shape.setAsEdge(new Vec2(-20.0f, 20.0f), new Vec2(20.0f, 20.0f));
ground.createFixture(sd);
// Bottom horizontal
shape.setAsEdge(new Vec2(-20.0f, -20.0f), new Vec2(20.0f, -20.0f));
ground.createFixture(sd);
}
{
Transform xf1 = new Transform();
xf1.R.set(0.3524f * MathUtils.PI);
Mat22.mulToOut(xf1.R, new Vec2(1.0f, 0.0f), xf1.position);
Vec2 vertices[] = new Vec2[3];
vertices[0] = Transform.mul(xf1, new Vec2(-1.0f, 0.0f));
vertices[1] = Transform.mul(xf1, new Vec2(1.0f, 0.0f));
vertices[2] = Transform.mul(xf1, new Vec2(0.0f, 0.5f));
PolygonShape poly1 = new PolygonShape();
poly1.set(vertices, 3);
FixtureDef sd1 = new FixtureDef();
sd1.shape = poly1;
sd1.density = 4.0f;
Transform xf2 = new Transform();
xf2.R.set(-0.3524f * MathUtils.PI);
Mat22.mulToOut(xf2.R, new Vec2(-1.0f, 0.0f), xf2.position);
vertices[0] = Transform.mul(xf2, new Vec2(-1.0f, 0.0f));
vertices[1] = Transform.mul(xf2, new Vec2(1.0f, 0.0f));
vertices[2] = Transform.mul(xf2, new Vec2(0.0f, 0.5f));
PolygonShape poly2 = new PolygonShape();
poly2.set(vertices, 3);
FixtureDef sd2 = new FixtureDef();
sd2.shape = poly2;
sd2.density = 2.0f;
BodyDef bd = new BodyDef();
bd.type = BodyType.DYNAMIC;
bd.angularDamping = 5.0f;
bd.linearDamping = 0.1f;
bd.position.set(0.0f, 2.0f);
bd.angle = MathUtils.PI;
bd.allowSleep = false;
m_body = getWorld().createBody(bd);
m_body.createFixture(sd1);
m_body.createFixture(sd2);
}
{
PolygonShape shape = new PolygonShape();
shape.setAsBox(0.5f, 0.5f);
FixtureDef fd = new FixtureDef();
fd.shape = shape;
fd.density = 1.0f;
fd.friction = 0.3f;
for (int i = 0; i < 10; ++i) {
BodyDef bd = new BodyDef();
bd.type = BodyType.DYNAMIC;
bd.position.set(0.0f, 5.0f + 1.54f * i);
Body body = getWorld().createBody(bd);
body.createFixture(fd);
float gravity = 10.0f;
float I = body.getInertia();
float mass = body.getMass();
// For a circle: I = 0.5 * m * r * r ==> r = sqrt(2 * I / m)
float radius = MathUtils.sqrt(2.0f * I / mass);
FrictionJointDef jd = new FrictionJointDef();
jd.localAnchorA.setZero();
jd.localAnchorB.setZero();
jd.bodyA = ground;
jd.bodyB = body;
jd.collideConnected = true;
jd.maxForce = mass * gravity;
jd.maxTorque = mass * radius * gravity;
getWorld().createJoint(jd);
}
}
}
/**
* @see org.jbox2d.testbed.framework.TestbedTest#step(org.jbox2d.testbed.framework.TestbedSettings)
*/
@Override
public void step(TestbedSettings settings) {
super.step(settings);
addTextLine("Use 'wasd' to move, 'e' and 's' drift.");
if(getModel().getKeys()['w']){
Vec2 f = m_body.getWorldVector(new Vec2(0.0f, -30.0f));
Vec2 p = m_body.getWorldPoint(m_body.getLocalCenter().add(new Vec2(0.0f, 2.0f)));
m_body.applyForce(f, p);
}
else if(getModel().getKeys()['q']){
Vec2 f = m_body.getWorldVector(new Vec2(0.0f, -30.0f));
Vec2 p = m_body.getWorldPoint(m_body.getLocalCenter().add(new Vec2(-.2f, 0f)));
m_body.applyForce(f, p);
}
else if(getModel().getKeys()['e']){
Vec2 f = m_body.getWorldVector(new Vec2(0.0f, -30.0f));
Vec2 p = m_body.getWorldPoint(m_body.getLocalCenter().add(new Vec2(.2f, 0f)));
m_body.applyForce(f, p);
}
else if(getModel().getKeys()['s']){
Vec2 f = m_body.getWorldVector(new Vec2(0.0f, 30.0f));
Vec2 p = m_body.getWorldCenter();
m_body.applyForce(f, p);
}
if(getModel().getKeys()['a']){
m_body.applyTorque(20.0f);
}
if(getModel().getKeys()['d']){
m_body.applyTorque(-20.0f);
}
}
@Override
public boolean isSaveLoadEnabled() {
return true;
}
@Override
public Long getTag(Body argBody) {
if(argBody == m_body){
return BODY_TAG;
}
return null;
}
@Override
public void processBody(Body argBody, Long argTag) {
if(argTag == BODY_TAG){
m_body = argBody;
}
}
/**
* @see org.jbox2d.testbed.framework.TestbedTest#getTestName()
*/
@Override
public String getTestName() {
return "Apply Force";
}
}