I'm working on this image. Viev from top, sky is reflected in a flattered cube with mirror surface applied to it. I inserted a negative terrain to give the idea of the hole. I'm stuck with it because I'm not able to give a sense of volume to the hole, and furthermore, I would like to give the idea of a broken glass in order to give movement to the scene. Can anybody help?

Replace the cube with a lattice object that's made from a greyscale map you've drawn with the hole included, and made cracks to look like broken glass. Texture that with the mirror tex to reflect your sky. Make everything behind the lattice black, and insert a negative light or two behind it to darken it. Make bits and pieces of broken glass out of lattices as well, just flatten them down to look as thin as possible, and texture those with mirror tex. Either scatter them round the hole and out, or multireplicate them along paths. That's how I would do it anyway

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.