title: SKPhysicsBody does not work on SKShapeNode
body: <p>I am drawing a ShapeNode using UITouch as below:</p>
  
  <p>The line draws correctly.  However, my problem is with adding the physicsbody to the shapenode(I want a SKSpriteNode to collide and bounce). But it's as if the physicsbody never attaches to the shapenode.  I've used YMCPhysicsDebugger to see where the physicsbody is, relative to the shapenode, but it doesn't detect anything.</p>
  
  <p>Has anyone encountered this before? How do you successfully add  a physicsbody to a dynamic shapenode?</p>
  
  <pre><code>`-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
  {
      touch = [touches anyObject];
      CGPoint positionInScene = [touch locationInNode:self];
  
      pathToDraw = CGPathCreateMutable();
      CGPathMoveToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
  
      selectorLine = [SKShapeNode node];
      selectorLine.path = pathToDraw;
      selectorLine.strokeColor = [SKColor greenColor];
      selectorLine.lineWidth = 10;
      selectorLine.physicsBody=[SKPhysicsBody bodyWithPolygonFromPath:pathToDraw];
      selectorLine.physicsBody.restitution=1.0f;
      selectorLine.physicsBody.dynamic=YES;
      selectorLine.physicsBody.usesPreciseCollisionDetection=YES;
      selectorLine.physicsBody.mass=0.2;
      selectorLine.zPosition=1.5;
  
      [self addChild:selectorLine];
  }
  -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
  {
  
   touch = [touches anyObject];
   CGPoint positionInScene = [touch locationInNode:self];
   CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
   selectorLine.path = pathToDraw;
  
  }
  </code></pre>
  
  <p>Thanks,
  Doug</p>