Halo 2 saw some much needed improvements to material processing. The user can now define a directory to search for a shader in a directory. The amount of flags was expanded and some new properties were added to help with lightmap settings.

Material naming and shaders

Intermediate files such as JMS or ASS files you export from your 3D software contain the material names you used. How Tool finds the shader from there varies depending on whether or not a shader_collection.shader_collection file exists and whether or not the material name includes a shader collection prefix. We will go over how this works in the shader_collection section. Be sure to always use lower-case names and do not exceed 32 characters.

When no shader tag can be found, Tool will instead assign a default. The file path for the default shader can be found at tags\shaders\invalid.shader

Shader collection

Shader_collection files are text based files that contain a list of prefixes followed by a directory. These prefixes can then be used at the start of a material name to tell tool what directory to search in for the shader tag. Find the file at the following path.

tags\scenarios\shaders\shader_collections.shader_collections

Don't get confused by the extension used by this file. This is a standard text file you can open up in notepad. You should be able to open it to view the contents and see the shader collections created for Halo 2's development.

Adding a new directory

Adding a new shader collection is very simple. Use the following steps in order to add your own shader collection:

1. Open the shader_collections.shader_collections file in notepad.
2. Scroll down to the bottom and add a newline if needed. Each prefix and directory you add should start on a newline.
3. Choose a prefix name. This string of characters should have no spaces. In this case we will use the name example
4. Once you've done that press tab once to separate your prefix from the directory.
5. Now add a file path to a directory containing your level shaders. In our example we will use scenarios\shaders\multi\example\shaders

You should have ended up with the following:

example scenarios\shaders\multi\example

Using a shader collection

In order to use a shader collection you will need to have your material name start with the prefix you wish tool to use. If we wanted to use our newly created example collection then we would name our material the following:

example metal_floor

In the case of our example we want the prefix to be the start of the material name. This will be followed by a space and then the actual material name. The prefix will be stripped from the material name on import. In the case of our example above Tool would strip the example portion of the material name. It would then look for a shader tag named metal_floor in the tags\scenarios\shaders\multi\example\shaders directory.

Shader referencing

There are a few ways Tool looks for shaders on import. Here are some of the following ways:

• If a shader_collection file exists and the imported file is a level then the only way to assign shaders is a shader collection prefix

• If a shader_collection file does not exist and the imported file is a level then Tool will instead scan the tag directory for a matching shader. Tool will be looking for a matching shader tag starting with the shaders folder in the level root directory from the tags folder.

• If a shader_collection file exists and the imported file is a model then Tool will first check for a valid shader collection prefix in the material name. If the prefix does not match or does not exist then Tool will check the model root directory for a matching shader tag in a shaders folder.

Special materials

These material names are hard-coded into the tools and have special meaning. They do not need shader tags.

Material symbols

Material symbols are added to the start or end of the material name and give the surface certain attributes or behaviours in-engine.

Material properties

Material symbols are added to the start or end of the material name and set some parameters for the lightmapper to use.

city metal_roof lm:2.5
city metal_roof lp:5
city metal_roof hl:1
city metal_roof ds:0.5

Let's break down the examples above one by one.

1. In the first example we are looking for a shader tag named metal_roof from the city collection. Any surfaces using this material would have their generated lightmap resolution multiplied by 2.5 making shadows much sharper
2. In the first example we are looking for a shader tag named metal_roof from the city collection. Any surfaces using this material that would have any emissive values multiplied by 5 making them much brighter
3. In the first example we are looking for a shader tag named metal_roof from the city collection. Any surfaces using this material would do something.
4. In the first example we are looking for a shader tag named metal_roof from the city collection. Any surfaces using this material would cut reflected light by half.