$dudvmapis now defunct and is replaced by the
Refractshader. Though, the
Watershader still uses a du/dv map for
du/dv maps are used for DirectX 8 refractions. If you're a Photoshop user, it's easy to create du/dv maps using nVidia's texture tools. 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.
- Open the normal map. First go to Colors->Negative Image (PaintShopPro) or whatever inverses all the colors in your paint program.
- Now go to Colors->Adjust->Brightness/Contrast (or your paint program's equivalent). Leave brightness at 0 (Photoshop tends to produce more accurate results with brightness set to -17), but raise contrast as high as it will go.
DuDv maps with only pure yellow, green, red and black tend to have some artifacts ingame. There you should mix it up a bit with the original normal map. In Photoshop this is best done by puting the normal map as a layer on top of you dudv image set opacity to 50% and blending mode to hard light.
That's all! Just save and you're done.