Well, "not exactly the same" is a mild expression... it gets completely spoilt when you try to simply rename .bum to anything else. If the .bum is nothing but a raw structure in order to add an uneven surface then you might get away with it, but if it is supposed to supply real details then better stay clear off this method. Look at this example: On the left there is the grayscale template (actually a black "mountain" on a "white" valley), in the middle there is Poser's .bum conversion, and on the right you'll see the grayscale version of the .bum. There is no more difference between the "mountain" and the "valley" because they have the same level of gray. If you want to go back from the middle picture to the left one, you'll need a very complicated filter.