I am starting to work with a Mudbox/Maya workflow and I am confused a bit. With a bump map, 50 percent grey does nothing, while lighter values bump up and lower values go down. With a displacement map, black does nothing and lighter values pull the mesh up, right? Does this mean that if you were to make a plane and carve a valley into it in Mudbox, Maya would need to raise the overall plane to make the valley? Am I missing something?