Fun simulation of a Chain in Android

In this post I simulate a Chain in Android using AndEngine & Box2D physics. Simulating a Chain is fairly straightforward. Initially I create a static point as an anchor point to suspend the Chain from

link[0] = new Sprite((float) 360, (float) 20, this.mLinkTextureRegion, this.getVertexBufferObjectManager());

linkBody[0] = PhysicsFactory.createBoxBody(this.mPhysicsWorld, link[0], BodyType.DynamicBody, FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(link[0], linkBody[0], true, true));

this.mScene.attachChild(link[0]);

Then I create succeeding links to the initial link with revolute joints between them as follows

// Add links to chain with revolute joint between each link

for(int i =1; i < nBodies ; i++){

x[i] = x[i-1] + 8 * Math.cos(PI/4);

y[i] = y[i-1] + 8 * Math.sin(PI/4);

link[i] = new Sprite((float) x[i], (float) y[i], this.mLinkTextureRegion, this.getVertexBufferObjectManager());

linkBody[i] = PhysicsFactory.createBoxBody(this.mPhysicsWorld, link[i], BodyType.DynamicBody, FIXTURE_DEF);

this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(link[i], linkBody[i], true, true));

this.mScene.attachChild(link[i]);

revoluteJointDef = new RevoluteJointDef();

revoluteJointDef.initialize(linkBody[i], linkBody[i-1], linkBody[i-1].getWorldCenter());

revoluteJointDef.enableMotor = false;

revoluteJointDef.motorSpeed = 0;

revoluteJointDef.maxMotorTorque = 0;

this.mPhysicsWorld.createJoint(revoluteJointDef);

Finally I suspend a monkey as the last body to the Chain.

I have added plated for the 2 walls (right & left) and also the floor as collisions can be detected between bodies.

@Override

protectedvoid onManagedUpdate(finalfloat pSecondsElapsed) {

// Check collisions

if(rWall.collidesWith(this) ){

x = this.getX();

y = this.getY();

bText.setPosition(x-40,y - 20);

bText.setText("Bonk!");

}

if(lWall.collidesWith(this)){

x = this.getX();

y = this.getY();

bText.setPosition(x + 20,y - 20);

bText.setText("Thump!");

}

if(floor.collidesWith(this)){

x = this.getX();

y = this.getY();

bText.setPosition(x - 20,y - 20);

bText.setText("Thud!");

}

With all these under gravity we have a nice Chain effect!

You see the video at Fun simulation of a Chain in Android - I

The project can be cloned from GitHib at Chain

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