In the GoldSrc games "Material" definitions handle what footsteps and what impact sounds are played against each texture in the game-world.

Generic bullet impact effect in Half-Life

So when you walk on dirt, you can hear the difference; or when you shoot wood with a gun it will sound like wood.

Note: While Nuclide supports this for legacy BSP files, please define the surface properties inside your material using the surfaceprop command.

Details

Usually, a game in the GoldSrc engine would provide a sound/materials.txt file, where each line defines the properties for a single (or a series of) textures by starting with a material id character, followed by whitespace, followed by a name matching pattern.

For example:

C CONCRETEWALL

Will give any surface the id C if it starts with the name CONCRETEWALL.

It will also only compare the length of characters of the name above. So for example if you were to define:

C CONC

Then CONCRETEWALL would still be marked as concrete, and any other texture that starts with CONC[...].

Note: In vanilla Half-Life, the second argument (name) can only be 12 characters long.

When you then walk around your level, the footstep will then be aware of you being on a texture marked with the C attribute and play a different step sound. Games are free to define what those material id characters mean - so different games/mods may interpret it differently.

Porting levels can sometimes be a bit more work than it first appears to be at first glance as a result!

Later Enhancements

Community additions

In stock GoldSrc games, the sound/materials.txt can be overwritten by a modification but it couldn't be dynamically extended in any way. This means there was no possibility of map specific materials, and mods could not inherit Half-Life's materials, so mods would always have to manage a nearly duplicate file if they desired custom material definitions.

A few mods tried to remedy this problem, the following below are methods documented so far:

file named maps/MAPNAME.mat : Introduced in The Wastes (2003)

file named maps/MAPNAME_materials.txt : Convention by Andrew Lucas, creator of Trinity SDK, modeled after MAPNAME_details.txt

worldspawn entity key named 'materials_file' with the value PATH_TO/FILE.txt : Introduced in Sven Co-op 5.0

All these methods are supported by Nuclide, as one goal is to implement conventions by not only Valve but the community as well!

Nuclide additions

In addition Nuclide has also implemented a way of giving modifications their own inheritable materials file:

sounds/materials_UNIQUENAME.txt

The idea here is that any mod or even map pack can include ONLY the textures used, and no longer will anyone have to manage a near-clone of sound/materials.txt.

For repackaging or modding purposes, if you desire to give your map custom material property definitions, we recommend The Wastes its method for individual maps, while the Nuclide method should be used for mods or map packs.

Note: We recommend only using material text files for GoldSrc related modding purposes. It is inefficient for modern projects as there are much better standards already supported in Nuclide.

Material List

In Nuclide, this is the currently supported list of material IDs:

Material ID	Material Name
B	Bloody Flesh
C	Concrete
D	Dirt
F	Flesh
G	Grate
H	Alien
K	Snow
M	Metal
N	Sand
O	Foliage
P	Computer
S	Slosh
T	Tile
V	Vent
W	Wood
Y	Glass

Game differences

Different games/mods can ship with different material properties. To make your life easier, you can edit scripts/surfaceproperties.txt and define which Material ID character maps to which surfaceproperty entry. This way you can add new materials to existing legacy maps without writing a line of code.

Listed below are definitions for various games and mods. Only the changes and additions are listed since the rest are identical.

GoldSrc Games/Mods

Arrangement

Material ID	Material Name
B	Blue Texture
N	Snow
R	Red Texture
U	Slime
X	Yellow Texture
Z	Black Texture

Counter-Strike

Material ID	Material Name
N	Snow
X	Grass

Afraid of Monsters: DC, Natural Selection, and Snow War uses the same definitions.

Cry of Fear

Material ID	Material Name
B	Random Twig Snap
H	Paper
I	Mud
O	Sand
P	Snow
R	Gravel
U	Grass
Y	Broken Glass
Z	Carpet

Gunman Chronicles

Material ID	Material Name
G	Wood
T	Rock
V	Sand
W	Unknown/Unused?

Firearms

Material ID	Material Name
B	Sandbag
N	Snow
U	No impact or decals, just smoke effects

Heart of Evil

Material ID	Material Name
U	Mud

Hostile Intent

Material ID	Material Name
A	Sand
E	Foliage
N	Snow
R	Carpet
U	Mud
Z	Grass

Household DEATH!

Material ID	Material Name
H	Wood (Creaky)
I	Grass

Night at the Office

Material ID	Material Name
T	Carpet

Opposing Force

Material ID	Material Name
O	Snow

Science and Industry uses the same definitions as Opposing Force.

Poke646

Material ID	Material Name
M	Metal/Grate
T	Wood/Tile
G	Carpet/Grass

Wasteland Half-Life

Material ID	Material Name
B	Barrel
I	Sand
N	Tinroof
R	Rust
U	Drywall

The Wastes uses the same definitions.

Source Engine Games/Mods

While Source has materials describing a surface with its own $surfaceprop command, the GoldSrc way of describing materials with a 1-character symbol is still used to define which impact effect to use.

The Material ID is used via the gamematerial command inside scripts/surfaceproperties.txt entries. In Nuclide that's used for compatibility with the GoldSrc system instead.

Be aware that a Source engine game may actually have more surface materials than this, these are solely the IDs associated with impact effects.

Alien Swarm

Material ID	Material Name
11	Steam Pipe

Alien Swarm: Reactive Drop uses the same definitions.

Counter-Strike: Global Offensive

Material ID	Material Name
11	Mud
12	Sand Barrel
13	Sand Barrel (Penetration)
14	Metal Shield

Half-Life 2

Material ID	Material Name
A	Antlion
B	Flesh (Bloody)
H	Flesh (Antlion)
K	Snow
L	Plastic
N	Sand
I	Clip
O	Foliage
X	Fake
-	No Decal

Half-Life 2: Episode 2

Material ID	Material Name
E	Antlion Egg Sacks
Z	Adviser Shield

Insurgency

Material ID	Material Name
A	Fruit

Day of Infamy uses the same definitions.

Left 4 Dead

Material ID	Material Name
J	Grass
K	Mud
Q	Asphalt
R	Brick
U	Cardboard
1	Clay
2	Plaster
3	Rock
4	Rubber
5	Sheetrock
6	Cloth
7	Carpet
8	Paper
9	Upholstery
10	Puddle

Portal 2

Material ID	Material Name
R	Reflective