Using Gimp to Create Ho Scale Model Railroad Buildings

As the cost of plastic kits continues to rise, here’s a great alternative way to build an HO Scale City on your model railroad.

Cobbling new buildings together from the remains of old plastic structures is both difficult and highly consumptive of old plastic parts – my supply just isn’t that great! Paper buildings are the way to fill out the backdrop of my HO Scale model railroad without breaking the bank.

There are several places online where you can download paper buildings in HO Scale – Poolside Rails, ScaleScenes, and Bastelbogen Online are three that come to mind. All three offer a fine selection of structures, many of which are for free. They’re easy to build and already detailed for you.

But I wanted LOTS of buildings to fill in the background of my model city. That’s when I discovered GIMP 2. It’s an open-platform photo manipulation program very similar to Adobe Photoshop. GIMP 2 is quite powerful, easy to use, and, best of all, it’s free! You can use it to design your own buildings in any scale you’d like. It’s quick and easy.

Before you start, however, you have to take a few measurements. GIMP works in pixels, so you need to find yourself a MM to Pixel converter – Unit Conversion.Org works well.

Your basic entry door in HO scale is 27mm/102pix tall and 10mm/38pix wide. A single story wall is usually 40mm/151pix tall and just as wide as you need – mine start at 133mm/503pix. The only other measurement I worry about is the basic distance from the sidewalk up to the bottom of my ground floor windows, the minimum of which I set at 6mm/23pix. Okay. That’s the hard part.

Open up a new drawing in GIMP. Be sure to give yourself plenty of room by setting the page size to 1000 by 1000 pixels. That’s a lot of room. Just a quick note that may answer questions about scale: all of the measurements we’re using are based on a resolution size of 96×96 dpi, which is the native format for GIMP. You don’t need to know anything beyond the fact that it’s all in 96 dpi.

First, select a rectangle from the toolbox and draw yourself a box that is 151 pix tall by 503 pix wide. Select the Bucket Fill option from the toolbox and fill the entire selection with a neutral color, like a cream yellow. Boom. There’s your first wall. We’ll call it the front wall of your building.

Open up a browser, open Google, go to Images, and type in the word “door”. Once you find a door that you like, open the preview and right click. Save the image to your clipboard. Open up Paint and paste the image there. Using the Rectangular Select button, outline the window itself. Now you can scale the window to the size you need. As you change the size of your selection rectangle, you’ll see in the lower right that the size of the selection is displayed in pixels in the lower right of your screen. Scale it down to 102×38 pixels and copy it to the clipboard.

Now go back to GIMP and paste the image in. Boom. There’s your door. Now you can go to Google and pick up windows and other features you’d like to display on your building.

The reason we’re going to Google to get our doors and windows, by the way, is for authenticity. Most of the images you’ll find on Google are photographs of real building hardware, with all of their imperfections. These images feature shadows and reflected light that’s quite difficult to convincingly draw. As the windows of your new building won’t be able to reflect light, being paper, why not let the photographs do it for you?

Once you’ve got your first floor looking the way you’d like it in GIMP, use your Rectangle Select button in the toolbox to select the entire floor. Copy the image to your clipboard, click somewhere else on the page, and paste in the image. Move the pasted portion so that it sits on top of the first floor and now you have your second. You’ll have to replace that door on the second floor with a window unless you’re into building fire escapes or having your tenants plummet to their death. Once you’ve got the door replaced, your second floor can be copied and pasted as many times as you’d like to build as big a building as you’d like.

On the right side of the wall, centered and about 2/3rds of its height, place a tall rectangle about ¼ of an inch wide so that it extends off of it. You do this by using the Rectangle Select button to outline your new tab and the Bucket Fill to give it some color. This will be the gluing tab to which you’ll stick the next wall.

Up at the top of the wall, use the Rectangle Select button to select its top 20 pixels and copy it to the clipboard. Now paste the selection onto your building so that it sits just a tiny bit above the wall – I usually leave a thin white line between the regular wall and this selection. This will be the inside of the top of the wall when youl fold it over.

At the very top of the entire wall, above your new selection, you’ll want to make another gluing tab that sticks at least ¼ inch above the wall. This will be your roof support tab. When you build the wall you’ll fold the wall extension down and glue it to the back of the wall and fold the roof support tab out. You’ll then glue the roof to that tab.

To actually build a building you’ll need more than just one wall. But once you’ve created that first wall you can copy and paste the entire thing to make a second wall. And a third, and a fourth. Change the details, using images you find on Google, to make it look authentic.  Reducing or increasing the width of your end walls, assuming you’ll use the wall you’ve already made for the front and back, is as easy as Rectangle Selecting the portions of the wall and either deleting them or copying them to shrink or expand it. Just make sure you rearrange your features, windows and things, to match the new size.

One little feature I like to add is a thin strip, maybe 20 pixels wide, that is the same height as each wall. I make four of them, fold them in half and glue one over each corner of the building to hide the seams. They’re almost invisible, improve the looks, and actually lend a lot of strength to the structure.

The roof is a simple rectangle with the width of the front wall and the depth of the side walls. I use Bucket Fill to in GIMP to fill it with a Pattern – you’ll see it under the Bucket Fill option. I use Slate because it doesn’t seem to repeat itself over a large area. Play with it and find a Pattern you like. You can add features like hatches and stairwells and air conditioners, but they’ll come out flat. I recommend going to your scrap plastic parts box for those items.

Printing from GIMP can be a little tricky. You want to print the image at exactly the same size you drew it – a variance will take you out of scale. I print a copy of the building in draft mode and in grayscale the first time to make sure it comes out right.

If your image is too large for a single piece of paper, use the Rectangle Select button to highlight one of your walls and cut it from the drawing. Open a NEW page and paste it there. Do that for each of your walls until you can get your drawing onto one piece of paper.

Once you’ve got your building printing at the correct size, print it onto some cardstock – I work with 80lb and it comes out fine. It’s a good idea to protect your finished print job with a coating of matte spray – artist’s fix works great.

Professional card builders will tell you to laminate your printed pages to a good stiff card, which will result in a stout building. Professional model makers will tell you to glue ¼ x ¼ wooden supports into your corners. I’m telling you that those are both great ideas that will result in a very robust structure. You could, in fact, use more pieces of ¼ x ¼ lumber to frame the tops and bottoms of your walls, resulting in a very durable building.

If you go to the Buildings page at Poolside Rails and download one of the free PDFs you’ll see a good diagram of how to assemble the building. The building in the PDF might give you a good idea of how to make your own.

Remember that these will most often be your background buildings, which means subtlety should be the rule of the day. But armed with these simple ideas and the powerful GIMP software you can build an entire city for the cost of the paper and ink!


Very strong article

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