Well, tat's one way to go (probably the best too) but if you want a quick fix, take it inot Photoshop or whatever you post process your work in and make a layer (if you can). Then just use the polygon lasso tool to copy shapes that would be the broken glass flying out from the image and paste them in the layer. You can then move them around freely and even make them transparent! As for extra volume in the hole, select the hole in Photoshop and then expand the selecyion by about 5 or so. Use the magic wand to deselect the blacks. Then use the lasso or the rectangle selection tools to deselect half the selection and all of the object that's breaking the glass. Then fill it with white at 50% or less. You may need to move the selection a little askew to get the feeling you want before filling.