Well, it's not as done as I would like, but I promised an update today, so I can't disappoint.
Right then. This section shows you how to turn this:
Into, well, twice of this:
Lovely, right? Right. The first step of this is actually the most important in the whole process. Think. Use your brain that God gave you. It is absolutely critical that your deckplans make sense in some fashion. If the ship is designed to be a transport, the majority of the ship should not be taken up by weapon emplacements or science bays. Using the text button, compile a list of the things your ship definitely needs, and keep it as its own layer. In general, your ship will definitely need the following: environmental controls, a galley, a head, and some sort of sleeping arrangement. As odd as it sounds, everything else is optional.
Highly recommended, but optional. Usually you can safely add a bridge, engine room, airlocks, power core, and storage areas to that list. Since I've decided the ship I'm building will be a medical vessel (as is evidenced by the clever naming of the file), my ship will also need several surgical bays, patient rooms, a lab, a pharmacy, a triage unit, and some sort of method for quickly getting patients in and out, among other things. Since it's medical, it will be lacking weapons, long-range sensors, more specific scientific bays, and similar superfluous areas.
Now that you've got a list, consider where you're going to put these things in relation to each other. People want to get from one area to another quickly, especially if you do it often. In space, you also need to keep in mind partitioning for loss of pressure, and that windows are not auxiliary means of egress from the vessel. Since mine needs to remain as sterile and clean as possible, I also need to keep in mind contamination vectors. Since it will be handling large numbers of patients in its role as a battlefield medic, it also needs a quick method to distribute incoming patients to where they need to go.
As for the actual method of building the rooms, it's much like the exterior bulkheads. create a new transparent layer, label it 'interior bulkheads' or similar, and place it above the exterior bulkheads in your stack (your stack of layers should read roughly from bottom to top as background-exterior bulkheads-interior bulkheads-slope lines [if you have them and they're not their own layer, give them one now. It'll be important coming up]). I generally make interior walls seven pixels in width, with areas needing more security at thirteen. I occasionally use 25 width on the inside of the ship, but only to separate critical areas from one another, and for the power core.
Speaking of... The Power Core: My first set of real directions in this tutorial.
-Choose a location and overall size for your core. Generally, I make mine anywhere from 180px (15ft.) to 600px (50ft.) in diameter. Use guides to plot the center of the core.
-Use the circle select to make the desired size, and center it on the core.
-Fill the selection.
-shrink the selection by 25px (I find that GIMP has a hard time extrapolating circles up and down properly, so you may want to give the selection a 'shake.' Simply move it around and center it again before moving on, and that sorts it).
-delete everything inside of it.
You should have something looking like this:
Nice, isn't it? Now:
-Select a small area at the center of the core, from 45-90 pixels, to be the basis for your core's... core.
-Now go to filters->render->Lava.
-Call on help from the Germans. For the gradient, we want 'German Flag Smooth' It might already be there, I'm not sure. Make it so.
-Select a circular area inside the center of the circle of lava, anywhere from 24-60 pixels, and invert the selection.
-Erase all the lava outside of it.
-Go to Colors->Desaturate, and choose the option that looks best to your eye.
For the following, on large images, you may want to make a new, smaller image and perform these there, then port it across. Gimp has a hard time with distorts on large images. If not, create a new layer, don't worry about the name and put it above your interior bulkheads.
-Select about 60 pixels larger than your core core (the small lava thing), and distort the selection, any values you like the result of.
-Fill the selection, shrink it by 1 pixel, then delete the interior.
-Repeat the above two steps, but at a size about 30 larger than your core.
-Merge the layer down, or import it into the main image.
You should now have something vaguely like this:
-Now, create a new layer (above the bulkheads), and draw a line with a width of 2 pixels straight down the center of the core, all the way to the outside. Make sure the center of this line is in the center of the core, else this will not work.
-Use the magic wand to select the line.
-CTRL+X, CTRL+V, while you can see the whole selected line. If you did it right, the line should be a floating selection right where it used to be.
-Rotate that 10 degrees.
-CTRL+V, you should have a new line where the old one started.
-repeat the above two steps,at rotations of +-10, 20, 40, 50, 70, and 80, for a total of twelve lines. You should end up with something that looks like a starburst.
-Go to the original bulkhead layer, the one with the core walls. Select the inside of it, and use the circle select on it to make it round.
-Go to your starburst layer.
-Shrink the selection by 24 pixels.
-Fill the selection.
-Shrink it by a further 2, and delete the interior. You should have something that looks like a circular sidewalk.
-Now, carefully erase the inside line in the areas where the lines are closer together (there should be 20 and 10 degree chunks made by those lines. you want it so that the circle is only still between the ones 20 degrees apart.
-Once that's complete, merge the layer down.
-Make a new layer.
-Using the paintbrush, run a line with a width of 5 pixels from the center of the jutty block things you've just created to the center of the core. Make sure they all meet in the middle.
-Select the whole thing, and shrink by one pixel. Delete what you've got selected.
-Shrink by one more pixel, and fill the whole selection.
-Run the blur tool along the lines, once each.
-Carefully erase the lines so that they end at the wall of the jutting blocks, and the outside edge of the first distorted circle.
-Merge the layer down.
Once that's done, you should have something close to this:
And that's the power core.