|1. Problem - picture has global lighting gradient from the bottom left to the upper right corner, so it's difficult to make the texture tile able. Even if you make it seamless tile able with a regular tiling technique, for example using a clone tool in Photoshop, it becomes checkered when tiled multiple times and seen from distant view.
Tiled initial texture:
Tiled initial texture. Distant view:
2. Now we will try to remove global gradient.
Open the initial texture (not tiled). Duplicate the background layer. Duplicate again. Blur the first copy several times using 250 pixels radius, until it becomes constant color. Select the other copy. Select the "High Pass..." filter from the "Other" category. Tune the radius setting. You need to bring the gradient out of existence. Smaller radius does it for sure, but you need to balance between small and high radius to remove the gradient, but still save the texture. In this example I used something about ~30. The layer gets generally gray with a little coloring. Now you will mix it back with the constant color, accumulated in the previous layer, but already without unwanted light gradient. Set the 'grayish' layer's mode to 'multiply'.
"Background copy 2" is the layer processed with "High Pass" filter. This layer has "multiply" mode. "Background copy" is the color accumulation layer. It is made by blurring a background copy multiple times.
Almost done, but you need to adjust the brightness, because multiply operation made the brightness in half. I recommend doing it with "Levels" adjustment layer.
"Levels" settings dialog:
If you now tile your texture, you will see that the problem is solved.
3. Seams still need to be removed. It can be done with a clone tool in Photoshop. It's a common technique and this process is falling outside the scope of this article. A seasoned texture artist could probably do better job then me at this point.
Processed texture with seams removed:
Now crop the center part of the image using Image/Canvas Size dialog...
Canvas Size dialog settings. Width: 50 percent. Height: 50 percent. Anchor: Center:
Texture before processing:
Texture after processing:
Texture after final seams removal with the Clone Tool:
Compare another two textures (COW skin)
Before "High Pass" processing:
After "High Pass" Processing:
* Project file demonstrates use in a After Effects project.