I have a habit of becoming far too complex in my explanations, especially when my relatively simple-looking maps are so intricate in their design. However, I'm going to try my best to put together a BASIC tutorial (so I don't waste too much of your time) for all you beginners out there, or perhaps veterans who might find this interesting, who seek to make a political world map and can't afford a more expensive program like Photoshop. (Though this can probably be done on Photoshop as well!)
(Note: Sorry I don't have visual aids right now, but I might make the time to post some later on if I get requests for it. I'm hoping my explanations will be clear enough by themselves.)
Step 1: The Basics
First, start a new project. Make the canvas size something longer than it is wide, preferably. On my main, most heavily-used fantasy world, I go with 5000x3400 pixels, but you may want to go bigger or smaller depending on your preference.
Next, make sure you have an understanding of layers and how to use them. If you're totally new to GIMP or just haven't used layers before, allow me to explain a bit. Layers are just that; different "layers" on an image. They can be hidden or revealed at any time, and are completely independent of one another. So, for example, if you draw a line on one layer and another line crossing it on a second layer, you can erase either of those lines without taking care not to erase the other. This is just one example, and it may not seem like much, but trust me: layers are an artist's best friend (a cartographer's, too!).
If you don't have your layer dialog box up, let's do that now. At the top of your main project window, towards the right end of the toolbar, you should see "Windows". Click this and go to "Dockable Dialogs". Then find and click "Layers". This should bring up your layer dialog. As a general rule, I position it to the far right of my screen and make it as tall as my toolbox, which is on the left... but you can position it however you feel most comfortable. (Note that you can use the "Recently Closed Docks" option to bring up the layers and a few MORE dialogs, but since we won't really be using any others, you might just want to go with the first option for simplicity's sake.)
Now that you have your layer dialog up, let's make a new layer. See the row of icons underneath the layers? Click the one that looks like a piece of paper to the far left. This will bring up a new box asking for a name, size, and fill type for the new layer. You can probably go ahead and leave the defaults for most of these settings, but if Layer Fill Type is for some reason not set to "Transparency", set it to Transparency now. Then let's name this layer "Coasts", and click OK. You should have a new layer named Coasts above the while Background layer. Good job! Onto the next step!
Step 2: Coastline
Your next step is to draw the coastline. For this tutorial, I'll only cover drawing out a single continent since other continents, islands, etc are all handled the same way. Make sure your tool color is set to black, then choose the Pencil tool (press "N" to bring it up quickly). Now choose your brush size. Under the Pencil tool's options, you should see a field that says "Brush". To the right of this is an icon, and to the right of the icon is a text box that has the name of the brush you're using in it. Click this box, then type the following: Circle (01)
This should give you a 1-pixel brush that we'll be using throughout the tutorial.
Important: Make sure you're using a PENCIL and not a PAINTBRUSH or Ink. This is vital because the Pencil tool has a hard edge with no fade-out, and we'll need this in our color fill steps on the next step.
Now, draw out a coastline. I won't go into detail on how to do this, both to save time and because I'm sure someone else in the guild has already given a better explanation somewhere.
Step 3: Filling in Kingdoms/Nations
Create a new layer again, and name this one "Political". Drag this one down below your Coasts layer (it's as simple as dragging and dropping, or you can use the down arrow icon below the layer list). This will be where your actual kingom/nation/faction color will go.
Select your Coasts layer again (just click on it in the Layers dialog). Now use the Fuzzy Select tool. Press "U" to bring it up quickly. Next, click anywhere outside your continent. This should select, well, everything outside your continent! Note that if you have multiple continents and some part of what would be the ocean isn't selected for some reason, you can hold Shift and click on that part to add it to the selection. Once all your oceans (and any lakes or seas you might've drawn inside the continent) are selected, go to your toolbar at the top and click on "Select", then "Invert".
Note: You could also use the Shift-click method to select INSIDE all your continents instead, which would not require you to invert the selection, but I find this method to be quicker and easier.
Now, go back to your Political layer and get the Bucket Fill tool (Shift + B to bring it up quickly). Now choose a nice, neutral color you won't be using for any of your kingdoms. I used black, since the text for my kingdoms was going to be black and it obviously wouldn't show up on a kingdom whose color was also black! Now, hold shift and click anywhere inside your continent. This should fill the entire continent with color (and any other continents as well, once you add them).
Next, look just above your layer list in your Layers dialog. You should see a checkbox option that says "Lock". (In older versions of GIMP, I believe it was "Preserve Transparency".) Check this box. (This is important!) Now get your Pencil tool back out and choose a color for your first kingdom; preferably one on a coast. Draw out any interior borders that kingdom may have, so that the kingdom is cut off from the rest of the continent by coasts and this line you've drawn. Because you've locked the transparency of the layer, you don't have to worry about going outside the coastline; draw as far out as you please. It won't show up because anything that isn't already filled with color has been locked.
Now get out your bucket fill and fill in the cut-off area that will be your first kingdom (without holding Shift; just click). Voila! The kingdom should be filled with color! Repeat this process for all other kingdoms, keeping in mind that you don't have to trace against borders you've already drawn. So long as an area is filled with a color other than black, it won't be affected when you use the fill tool.
Now in the story I use my primary map for, countless generations are covered and war is frequent. Territorial disputes and the rise and fall of empires are all inevitable. If your story is like this, you're in luck! Cutting into territory is simple. Simply select the color of the invading empire and draw into the conquered empire's territory just like you did to create kingdoms on the map, then fill the conquered section. Simple! You can use the same method to draw up new kingdoms that rebel from an existing empire or the like.
- I try to keep in mind certain aspects when drawing out kingdoms. Just loosely in my mind. These include past border disputes and their outcomes, natural barriers such as rivers and mountains, general locations of resources, etc. As a rule, your kingdoms' borders should be as curvy and gnarled as your coastlines.
- I advise against using full-on red for a color as it's too contrasting with other colors. It'll appear to pop out of the image if placed next to a color like blue and might even hurt your eyes! As a general rule for most colors, especially red, take the Value (the "V" bar on the color change box) down to at least 85 or so to be safe.
- If you use similar colors for two kingdoms, which you will inevitably have to do if you have a lot of them, make sure they're easy enough to tell apart. You can always change this later with a simple bucket fill!
- Note that if two empires with VERY similar colors are close to eachother and you try to fill one a different color, both may get filled. This is easy to fix. Simply find Threshold near the bottom of your Bucket Fill's options and drag it left until it hits 0.
Step 4: Other Ideas
Congratulations! You've finished the primary product! You can now hide the Coasts layer by clicking the eyeball to the left of the layer on your Layers dialog, or leave it revealed if you please. It's up to you. From here, you may considering adding more elements (in fact, you probably should!), but let me point out that you should always make a new layer for each different element. This ensures that not only your kingdom fills, but also your different features, are kept safe from changes made to another aspect of the map. In other words, you can draw in mountains on one layer without having to worry about them when it comes time for a new empire to conquer the land these mountains make up.
For an idea, I have the following layers on my map:
Provinces (for sub-territories and fiefdoms inside an empire)
Terrain (mountains, forests, etc)
Features (the names of mountains ranges and whatnot)
Small Faction Names
Faction (Empire) Names
This is also convenient because you can show and hide layers at will. So if you want to see just the cities on your map, hide the other name layers. If you just want to see empires without the clutter of terrain, hide everything but the political and empire name layers.
My techniques have been given (to some small extent). From here, it's all up to you to adapt them to your style and build upon them. I hope this was helpful to you. Good mapping!