This section deals with making seamless textures from images that have patterns but can't be used as tiled texture maps because their edges don't match. It will be worth working through this part of the tutorial even if you don't plan on making your own textures, because it introduces the power of The Gimp's 'Offset' command, as well as explaining how to use the Clone Stamp tool. We will also be using the finished texture that you make in this section to create a bump map in 'Easy Bump Mapping'.
1) The first thing you need to do is download the Original Non-Seamless Texture above (right click on it, then select 'Save Target As') and save it into the bitmaps folder of your map directory. For example, if you were making a map called 'Box', you would save the picture in: HaloCE\data\levels\test\box\bitmaps.
2) Load the texture into The GIMP using the File>Open menu at the top of the main window.
3) As you can see from the second picture above, the edges do not match and so the texture looks terrible when it is tiled. What we need to do is cut out an area where we know the texture repeats itself. Looking at the image, we can see that the pattern is repeated for every one brick width horizontally, and every two layers of brick vertically.
While we could easily make a tileable texture from just one of those red squares, this is something that you will usually want to avoid doing. The reason for this is that when you restrict your texture to such a small sample, it lacks variety when it is tiled. In short: it looks fake and unnatural.
So, we will want to select a large area of pattern repetition using the Rectangular Region tool in the top left of the toolbox, as shown below.
4) Select an area of the image like that indicated in the example picture below. It doesn't matter if you don't get it 100% correct, we will be editing the edges later on anyway. You may want to zoom in for better accuracy (the Zoom tool is directly below the Rectangular Region tool).
Note that I have avoided the black line of mortar in the top of my selection area, but included it at the bottom. Likewise, I have avoided the mortar lines at the left hand side, while including them on the right. If you don't do this then your pattern will have both sets of mortar lines when it is tiled. This results in two black bands and a number of smaller bricks. Not good.
5) Copy the selected area of the image by selecting Edit>Copy from the menu above the image.
6) Create a new window by selecting File>New from the menu, then hit OK.
7) Paste the selected area of the image into the new window by selecting Edit>Paste from the menu.
8) From the menu above the image, select Layer>Transform>Offset. Press the button marked 'Offset by (x/2),(y/2)', then hit OK. Your image should now look something like this:
What this has done is taken edges of the image and pushed them together so you can see how they line up. This is exactly how the edges of your texture would look when tiled in-game. You can see that although the seams match up pretty well, there are some very noticeable differences in colour.
Now we come to the real power of the 'Offset' command: we can edit the image in this state to make it appear as though it were a naturally tiled texture.
Holding down the mouse button while moving the mouse will also draw the area around the point you designated, up to the maximum number of pixels indicated in the 'Fade Out' section of the Clone Options (the default is 100 pixels). Letting go of the mouse button then drawing again will cause the cloning to reset back to the point you designated.
11) Use the Clone tool to get rid of the harsh edges by painting across them from different sides. You'll want to use a lot of different cloning points to a get natural non-repetitive seam. Check the picture below to see how the edges and colours are much smoother on the top half, which has been worked on, compared to the bottom, which has had nothing done to it.
Don't be afraid to use clone points from anywhere on the image in order to get a good result. The only rule here is: If it makes the seam look like a naturally tiled texture, it's fair game.
The example here doesn't have a horizontal harsh edge because the way original image was cut, it lined up nicely on the top and bottom. If you have a horizontal edge, you would use the Clone Stamp tool on it just as you have done to the vertical edge.
12) Once you're happy with the way the edges look, you'll need to return the image back to normal by using the 'Offset' command again. From the menu above the image, select Layer>Transform>Offset. Press the button marked 'Offset by (x/2),(y/2)', then hit OK.
13) Before the texture can used with Halo, the pixel size must be a power of two (ie. 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 or 2048 pixels in width or height). The image I have is 256x346. Yours may be different by a small amount, but that doesn't matter, we're going to be converting it to a 256x256 pixel texture.
From the menu above the image, select Image>Scale Image. In the window that pops up, make sure that the top chain link is broken (so that the width and height are not linked), then enter 256 into the New Width box and 256 into the Height box. Click on OK.
14) The texture is now ready to be saved as a .tif file (the Halo Editing Kit requires textures to be save as .tif files). If you've used more than one layer in your image (it tells you how many layers you're using in the blue window at the top of the image), then you'll need to merge them all using Layer>Merge Down before saving.
Save the file in the same directory that you loaded it from. You're now ready to create a basic bump map for this texture, so move on to the next section.