Normal Maps (Bump) Editing and Creating.

A user who uses gimp worked out how to do the changing the channel color step in gimp and has been kind enough to let me post it here. Thank you christina51.

Open the image of your diffuse map in GIMP.


Select Filter>Map>Normalmap. When the Normalmap pop-up appears, select Filter and choose one of the options (e.g., Sorbel 3x3--I chose this because it looked "best"...I don't have a clue what any of it means). Hit OK. (There are lots of other things you can do but since I don't know what they mean, I just stuck with the basics.) Anyway, this results in “blue” map like in your example, which needs to be converted to gray as follows.


Select Layer>Transparency>Add Alpha Channel. (I guess some images might already have an alpha channel but the ones I've worked on didn't.)


Select Colors>Components>Decompose. In the Decompose pop-up, select RGBA from the Color Model dropdown and check the box for Decompose to Layers. Hit OK. This will open a new window with a gray copy of the map. This is the copy you will work on for the next steps.


In the Layers dialog box (left dockable) for the gray image, you should see four layers (red, green, blue, and alpha). You need to copy the red layer into the alpha layer and then the copy the green layer into both the red layer and blue layer (as you did in your example), like this:


Select the red layer (click on it) and copy it to the clipboard (Ctrl A, Ctrl C). Then, select the alpha layer (click on it) and paste the contents of the clipboard into it (Ctrl V, Ctrl H).


Select the green layer and copy it to the clipboard (Ctrl A, Ctrl C). Select the red layer and past the contents of the clipboard into it (Ctrl V, Ctrl H). Select the blue layer and paste the contents of the clipboard into it (Ctrl V, Ctrl H).


Still in the gray window, select Colors>Components>Recompose. This will change the image in the original window to a gray image with the transparency checks.


Now select the original window (one with the transparency image) and Export as a .dds image (BC3/DXT5, Generate Mipmaps).


Open S4S and open your project. Select the Warehouse tab. Find the DST Image for the current normal/bump map. Import your normal map (the .dds file you just exported) and you're done. There is no need to export the original/EA’s bump map first…just import your new one and it will replace the old one.



simslewds have you read that? 
I dont know nothing about gimp, but maybe has an answer above.