Strange, because changing the file extension worked for me ??? You also have to change the extension(s)in the pz2 file of course. Or otherwise there is the "simplified method of making your own bump map" : 1 -> load the texture (with changed extension) in a picture editor. 2 -> make it black & white. 3 -> enhance the contrast (more black/white, less grey). 4 -> save as a jpg under another name. Step 3 is not an absolute necessity, this method works for making trans maps too. I don't know any but maybe there is also some utility doing the conversion for you if your "bunch" is too much to change manually.

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