Creating a Decal Material

This guide will show how step by step how to create a decal material. The process consists of two parts, first, creating the source decal material in Photoshop. The second part is converting this Photoshop image into a format recognized by the game engine, there is a standalone tool that takes care of this part.

A source decal material is a Photoshop file that will contain one layer per decal. The alpha channel is shared by all the decals, which means there can�t be any overlapping layers. For efficiency, layers should be sized in powers of two (32x32, 64x62, 128x128, etc).

Part 1 � Creating the source decal texture with Photoshop

Start by creating a new 512x512 image in Photoshop.

Go to the �Layers� tab and click on �Create a new Layer�. The �Background� layer should be left empty, you can lock it if you wish, and it is recommended that you hide it.

Right click on the layer name (the area highlighted in blue) and select �Layer Properties�, the layer name will represent the decal name, so name it something meaningful and easy to remember. In this example, we name our decal �ConcreteBlast�.

Right click on the layer again, this time select the option �Blending Options�, THIS STEP IS VERY IMPORTANT, if you forget to do this, the alpha channel will not get exported correctly and decals will look opaque or may not show up in the game. In the dialog that appears, uncheck the option Transparency Shapes Layer. YOU MUST DO THIS FOR EVERY LAYER THAT YOU ADD. Don�t forget.

Now you can draw the decal into the first layer. As a suggestion, select the area that represents the size of the decal. In this example I selected a 128x128 area, and pasted an existing blast mark decal into it.

Now we need to add the alpha channel for the image, click on the �Channels� tab and then click on the �Create New� button. This will add an empty (all black) alpha channel. Remember that the alpha channel is shared by all decals, so you must be careful of placing the alpha information for each decal in the right place. This is another area in which working with a grid is very handy.

Now draw the alpha for this decal, make sure it�s correctly placed under the correct decal layer.

Now that you have one decal correctly setup, you can add a new one. It can be of a different size, as long as it doesn�t overlap with existing decals, and that it has a power of two size.

The following is an example of what a decal texture with more than one decal would look like. Notice how it�s possible to have different sized decals anywhere in the texture as long as they do not overlap.

The layer set for this decal texture is the following.

And here�s what the alpha channel for this decal texture looks like:

Finally, you need to save out this decal texture as a Photoshop PSD file. Make sure that the �Layers� and �Alpha Channels� options are checked:

Part 2 � Exporting the decal texture for use in the game.

To export the decal texture into a format used by the game you need to use the �Decal Material Tool�

Start by setting the �Source Decal Texture� which is the Photoshop PSD file, you can use the browse button to look for it. Then select the destination file for your decal material. This tool will create two files, a file with a .dmat extension and a .tga file with the image data. The two files will have the same name and will be placed in the same folder as the destination path.

Click on the �Create Decal Material� button, if everything worked correctly you should see a message such as this:

Generated files:

materials\decal_texture.dmat

materials\decal_texture.tga

Complete!

When you�re done, you can click on the �Exit� button to close down the decal material tool.

PART 3 � How Decal Materials are used in-game.

Decals are applied in the game using collision materials, this means that the collision response spreadsheet must be setup to use decals. Open the collision response spreadsheet, usually at:

collision_materials\collisionresponse.xls

which is stored in the rez file:

main\pak0.rez

Open the Material Properties sheet, now look for any instances in which the Command is blastmark this command will be used for decals, so in the FX Alias for a blastmark you will write the decal name you want to be applied when an explosion goes off on a surface of a given material name.

Example:

Command�������������������� Material Name������������ FX Alias����������������������� Snd Alias

���

���

blastmark������������������� Concrete�������������������������������� Concrete_Blast

���

���

���

blastmark������������������� Grass�������������������������������������� Grass_Blast

In this case, when an explosion goes off on a Concrete surface, the decal that was named �Concrete_Blast� in the decal material will be applied. If an explosion goes off on a grass surface, it will then apply the decal associated with the name �Grass_Blast� in the decal material.