Newbies Guide to Alpha Channels and Layers:

You will need to know about these in order to make custom maps for Dawn of War.

Alpha maps:

Alpha maps are 2D greyscale images. Here are some examples:

They are used for two purposes in Dawn of War:

• Heightmaps
• Transparencies

Here is an example of the checker pattern alpha map being used to define the height of a terrain sheet in the editor:

(Dont worry about being able to do this for now, it will be explained later).

Here is an example of alpha maps being used to define transparency:

On the left is a standard Relic decal depicting a crater, with the standard Relic alpha channel dictating which parts are transparent. At the top is the decal graphic with no transparency, and on the right is the same decal graphic using the checkerboard pattern from the alpha channels shown above.

Because alpha channels are made from black, white and 254 shades of grey, they allow you to define 256 different levels of height when making an alpha channel for terrain, and 256 levels of transparency when making alpha channels for texture art. As you can see above, the Relic crater decal blends smoothly with the background because it uses shades of grey.

Don't worry if you don't understand what decals or heightmaps are, that will be explained in a later part of these tutorials.

In terms of alpha transparency: White is opaque, black is transparent, and all shades of grey depict varying translucency. In terms of terrain height, white is highest and black is lowest.

Layers:

Layers are an important concept in mapping for DoW, because the terrain is made from several of them. Anyone with experience of Adobe Photoshop will probably find it very easy to understand how they work in the Dawn of War mission editor.

For those unfamiliar with them, think of a single image made from several sheets of glass placed on top of each other; each sheet bearing a single part of the image, which in turn occludes some of the image on the sheets below. By way of a quick example, in the image above that shows craters, the crater decals are on one layer, and the blurry pattern that surrounds them is another layer which sits below. This separation means that you can manipulate the different layers of terrain quite independently of each other, the only real dependency being that all of them will conform to the alpha channel that dictates the shape of the terrain.