# 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

You can see the video at Fun simulation of a Chain in Android – I on Youtube

The project can be cloned from GitHib at Chain

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

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);

revoluteJointDef = new RevoluteJointDef();

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

Take a look at some cool simulations using AndEngine & Box2D
1. The making of Total Control Android game
2. Simulating an Edge Shape in Android
3. Simulating a Web Joint in Android
4. Modeling a Car in Android
5. A closer look at “Robot horse on a Trot! in Android”
and a couple more