3 point lighting can make things look flat due to the use of both a key and a fill light. Try using the 2 point lighting if you want to define shapes better (bump especially flattens out almost completely in a standard 3 point lighting situation (it does somewhat in real life too, that's why there are so many wrinkle free old people on film)). Remember that the backlight (can't remember its english name, but it defines the edges of an object to draw them out of the background to give more dimension to an image) should be placed almost directly on the camera axis (so it should have an almost exact opposite position of the camera to the object it is lighting).