The big difference for P4 users is the handling of bump maps, and if the MAT pose files I see installed are any guide, the change came with the introduction of ProPack. In P5 and later there are three different ways of using textures to make surface variations. Gradient Bump is for the P4-style bumpmaps, the .bum file, and you have to user the Poser 4 renderer. It won't work with Firefly. In Firefly, the Bump Map is a greyscale, usually a .jpg file, doing the same shifting of normals to give an illusion of surface roughness. Black is low, white is high. The Displacement Map actually moves the surface. An example: Victoria 3 has a Wrist Spandex morph, which gives a raised edge at the wrist, matching the edge of a material zone, so you can create the edge of a tight-fitting sleeve. A displacement map can give you the same step in the surface, when the model is rendered, without any need for a morph. A bump map will look like a step where the surface faces towards you, but you don't see any step in the surface as it curves around the wrist.