title: Coordinate system and sprite transformation
body: <p>I'm using andengine to create a physic simulation via box2d.</p>
  
  <p>The bodies are created through PhysicsFactory using Sprites.</p>
  
  <p>My idea is to procedurally position these sprites, following this pattern:<img src="https://i.stack.imgur.com/LaSoQ.png" alt="rotation around externalPoint"></p>
  
  <p>basically one central sprites which represent my world coordinates center, and a series of cloned sprites that are created by rotating the base sprite around myWorld center (the "X" inside the circle).</p>
  
  <p>I've tried to use opengl way inside andengine (translate, rotate, back-translate) </p>
  
  <pre><code>super(stamiRadious, 0, image);     //stamiDoadious is te distance from radix (world center) and "petal" attach point
  this.setRotationCenter(0, 0);
  this.setRotation((float) Math.toDegrees(angleRad));
  this.setPosition(this.getX()+radixX, this.getY()+radixY);
  </code></pre>
  
  <p>but i failed: results are not right (wrong final position, and wrong box2d body property as if the sprite is much larger than the image)</p>
  
  <p>I belive part of the problem relies on my interpretation on <code>setRotation</code> and <code>setRotationCenter</code>, and in general on my understanding of andengine coordinates system + box2d cordinates system.</p>
  
  <p>Any thoughts/links to doc/explanation?</p>