Du/dv map

If you're a Photoshop user, it's easy to create du/dv maps using nVidia's texture tools. (du/dv maps are for DX8 refractions.) But if you're using another program like PaintShopPro, you might have trouble getting the nVidia tools to work. Fortunately, a du/dv map can be easily created from a normal map in just two steps. You can also do this in Photoshop if you don't want to bother with the nVidia tools.

1. Open the normal map. First go to Colors->Negative Image (PaintShopPro) or whatever inverses all the colors in your paint program.
2. Now go to Colors->Adjust->Brightness/Contrast (or your paint program's equivalent). Leave brightness at 0, but raise contrast as high as it will go.

That's all! Just save and you're done..