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Let's learn how to create a very basic decal: an aircraft identification number. This will be exactly like the standard numbers ThirdWire included with the game, such as usnattacknum, usmcnum, etc. In fact, let's use usnattacknum000.tga as our guide. You can extract it from objectdata.cat and open it in Photoshop to have a look.


Its very exciting:





That's because all you can see initially are the Red, Green and Blue (RGB) channels, which in this case give you a black background. But wait, that is three 8-bit channels for a total of 24-bits. Strike Fighters uses 32-bit TGAs for decals, so where are the other 8 bits? Look to the lower right of your Photoshop screen and notice the menu with three tabs, Layers, Channels and Paths:





Click on the tab labeled Layers and the mystery is revealed. The other 8-bits are reserved for the alpha channel, which is present but hidden by default.





Here is the thing about the alpha channel: it acts like a mask. Anything that is masked off will be invisible in the final decal, and anything that is not masked off will be visible on the aircraft. The alpha channel does not have any "color" itself, but by default it is represented in red. You can both paint and erase on the alpha layer the same as you would on the RGB layers. Anything that you paint over will be masked, and any areas that you erase will be unmasked.


So go ahead and click in the empty box next to the alpha channel. An eye will appear in the box and the alpha layer will be reveled in the image on the left.


Now you can see the alpha channel, or mask, laid over the black background, and it becomes obvious how this whole thing works. Everything is masked off except the number "300" which means that a nice 300 modex will appear on the aircraft in game.





Now let's make a copy of this decal on our own. Create a new image with the following settings:





You will wind up with a little 64x64 pixel image with a transparent background. Zoom in on the image to 300% and paint the entire background black. It will look like this:





Now for the magic. Switch to the Channels tab and note that there is no alpha channel...yet.





We need to add an alpha channel. Look at the menu to the right of the "Paths" tab very closely. There is a tiny little down-arrow there. I've pointed it out in the screenshot below:





Click on that little fellow and a menu will open. Select, "New Channel" from that menu and dialog box will appear. Make sure the settings are exactly like in the screenshot below, and click OK.





If you have done everything right, you will now have a new alpha channel which is visible, and you RGB channels have become invisible. Your image is still black.





Go ahead and click the empty box next to the "RGB" channel at the top of the list. This will revel all three color channels, Red, Green, and Blue. Now you are almost there, you have an image with an alpha channel overlayed. If you were to save this decal and use it on an airplane, it would be completely invisible, because the entire image is masked.





So let's finish up. Make sure the alpha channel is the selected channel, it should be highlighted in dark blue.





Select the Text tool and pick an appropriate font (USAAF Code from McFly Aviation is the same as the one used for the stock decals). Set the font size to 30 (if you are using USAAF Code) and click once on the image. Type the numbers "300" and then select the Move Tool (its the arrow icon at the top of the toolbar).





You'll notive that after you click on the Move Tool, the numbers you typed disappear and are replaced by a flashing marquee. This is OK. Before we move on though, use the arrow keys to position the marquee as close to the center of the image as possible:





DON'T DO ANYTHING ELSE. You need to maintain that marquee for the next step, and selecting other tools or clicking on the image could make it go away.


One more step and we can save the image and get a beer. Select your Eraser Tool, and set the brush size up to about 30. With the marquee still in place, run the eraser tool over it until the red alpha mask is gone and you can see the black color beneath:





That's basically it. Now you can press CTL-D to get rid of that marquee and see your perfect 300 decal:





Now simply save your image as a 32-bit targa (do not select the RLE compression option) and try it on an aircraft.


This is just one way to make a decal, but I hope you have seen that the key to making it work is to use the alpha channel to mask off the areas you want to be transparent in-game.


One last tip: always leave at least 2 or 3 pixels masked off around the entire edge of the decal to prevent strange behavior in-game.


Good luck!

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