duplicate the image in the comp. create a mask shape around the window (with the pen tool)on the duplicate layer. then apply shatter to that masked layer, the effect will only happen on the masked area.
if you wanted to show something behind the window, copy the mask and paste it onto the lower layer/image. hit ‘m’ to show the mask properties and choose subtract from the mask pulldown. this will knock a hole in that layer.
now you can place an image/footage/comp behind that layer to reveal what is inside the house, after the window shatters.
if you notice a slight line around the window, where the masks are effecting the image, you can adjust the mask expansion a little to fill in the gap.
Kevin Camp
Designer – KCPQ, KMYQ & KRCW