Tutorials
Using Paint Alpha
Paint Alpha is an excellent tool that is used on displacement (terrain) and what is does is allow you to change the look of the texture to a more realistic worn look. In this example I will be using a grass texture, when combined with Paint Alpha it changes to a muddy brown for a worn look,
The textures that support this have a prefix of blend.
So first of all setup some terrain like so (refer to the terrain tutorial on how to do this):
Next go into your displacement menu like normal and choose Paint Alpha while the surface is selected
Then click around the areas that you want the worn look to go, different textures will have different effects. Once you have finished you should have a worn effect like so:
You can also Invert Alpha to swap it around, once you have played around you can come up with something like this:
Related:
Example Map
Blink