Post 3: Then Let's Begin (if I have an idea)
Now that the environment is set up, it is time to begin. At this point you may have a rough sketch of a map, either drawn on paper or on the computer. Here is the rough sketch I will work with for this tutorial:
I was doodling a coast-line with a crater like shape, and decided to put places around it line the numbers of a clock. This will be my starting point for The Region of Closh
Load this image into GIMP, and scale it to the page size you want. I’ll keep this one smaller (500x500) to make the tutorial more manageable, but it can be as large as you want. Ensure that the image is RGB, and the size you want. You may have to adjust some of the techniques (scaling, bump mapping amounts, etc) depending on the size and scale of your map.
Now create a new transparent layer (Layer->New Layer) and name it “Land”, pick a big, solid brush in black and trace out the contours using the Pencil Tool, then fill the area you want land in black, and everything else white.
GIMP TIP! – You can drag a colour from the palette or the color selector to an image and it will fill the current selection with that colour.
Now invert the layer (Color->Invert) and blur the image (Filters->Bur->Gaussian Blur) The amount of blur will determine how random the final coast will be. The larger the blur, the more random the coastline will be (in the blurry area). If you have a well defined coast already (like here) use a smaller blur (50px). If you have a poorly defined coast (as is the case when using a random coast technique) make it a large blur.
I went back and blurred a few areas more by hand on the main coast to get more randomness there but keeping the detail in the island ring. Note the histogram. What you want is a nice level image, with dark and light more evenly spread out, as opposed to a U shape.
Create new layer called “Land Noise” and fill it with clouds (Filter->Render->Clouds->Solid Noise) Set the detail to the maximum (15) and the X and Y size to the max (16.0). The larger the size, the more randomness your final coast will have. Give it a new random seed and jot down the number (I put it in the layer name afterwards as a reminder). And change the blend mode to Overlay.
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