Clipping rectangular button frame to image mask for use with UIDynamics

I have three buttons on my screen which have background images set in storyboard, the background images are hexagonal shapes. I'm currently playing around with gravity, when a button is pressed I want them all to fall to the bottom of the screen. I would like the buttons to react like they are hexagonal shapes when bouncing off each other rather than the rectangular shapes they are.

Is there a way to clip the UIButtons.frame to the hexagonal.png?

- (IBAction)home:(id)sender {

    animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
    gravity = [[UIGravityBehavior alloc] initWithItems:@[self.youtuberLyr, self.gameLyr, self.homeLyr]];
    [animator addBehavior:gravity];

    collision = [[UICollisionBehavior alloc] initWithItems:@[self.youtuberLyr, self.gameLyr, self.homeLyr]];
    collision.translatesReferenceBoundsIntoBoundary = YES;
    [animator addBehavior:collision];

    barrier = [[UIView alloc] initWithFrame:CGRectMake(0, 1024, 768, 0)];
    barrier.backgroundColor = [UIColor redColor];
    [self.view addSubview:barrier];

    CGPoint rightEdge = CGPointMake(barrier.frame.origin.x + barrier.frame.size.width, barrier.frame.origin.y);
    [collision addBoundaryWithIdentifier:@"barrier" fromPoint:barrier.frame.origin toPoint:rightEdge];
}

I have tried googling to no avail. Any help is greatly appreciated.