According to the Poser 7 manual, when I look up Gradient Bump, I'm told it's for using P4 bump maps when rendering in the P4 render engine. Gradient Bump: Previous versions of Poser used a proprietary file format for bump maps (.BUM). If you want to use these older file types in Poser 7, connect an image map node to the Gradient_Bump attribute and load your desired *.BUM file into that node (see “Image Map” on page 335 for information on loading images). Then, select Poser 4 Renderer in the Render Settings window and check the Ignore Shader Trees checkbox. Please refer to Chapter 37: “Using the Poser 4 Render Engine” on page 364 for more information on the Poser 4 renderer. You cannot use .BUM files with the FireFly renderer. Is the manual wrong again?