title: How to detect collision but do not collide in box2d?
body: <p>How to detect if body collides other body but do not react on this collision. </p>
  
  <p>By <em>default</em> i - detect collision and bodies collide. </p>
  
  <p>If i set fixtureDef filter - bodies do not collide but i can not detect collision. </p>
  
  <p>Help please!</p>