title: Draw a line with a CALayer
body: <p>I'm trying to draw a line between two points using a CALayer. Here is my code:</p>
  
  <pre><code>//positions a CALayer to be a line between a parent node and its subnodes.
  
  -(void)makeLineLayer:(CALayer *)layer lineFromPointA:(CGPoint)pointA toPointB:(CGPoint)pointB{
      NSLog([NSString stringWithFormat:@"Coordinates: \n Ax: %f Ay: %f Bx: %f By: %f", pointA.x,pointA.y,pointB.x,pointB.y]);
  
      //find the length of the line:
      CGFloat length = sqrt((pointA.x - pointB.x) * (pointA.x - pointB.x) + (pointA.y -     pointB.y) * (pointA.y - pointB.y));
      layer.frame = CGRectMake(0, 0, 1, length);
  
      //calculate and set the layer's center:
      CGPoint center = CGPointMake((pointA.x+pointB.x)/2, (pointA.y+pointB.y)/2);
      layer.position = center;
  
      //calculate the angle of the line and set the layer's transform to match it.
      CGFloat angle = atan2f(pointB.y - pointA.y, pointB.x - pointA.x);
      layer.transform = CATransform3DMakeRotation(angle, 0, 0, 1);
  }
  </code></pre>
  
  <p>I know that the length is being calculated correctly, and I'm am pretty sure that the center is also. When I run it lines are displayed that are the right length and that pass through the center point between the two points, but are not rotated correctly. At first I thought that the line was being rotated around the wrong anchor point, so I did: <code>layer.anchorPoint = center;</code>, but this code fails to show any lines on the screen. What am I doing wrong</p>