Making a custom breakable surface
Note:This so far has been tested in Half-Life 2 
in the 2009 branch of the Source Engine and Team Fortress 2 
, but in other Source games where this entity is fully functional, this should still work.What you need
You will need:
- A VTF editor/maker (VTFEdit was used in the making of this tutorial, but VTEX can be used also.) to manipulate the textures as .VTF files
- A VTF texture to represent the intact material
- A VTF texture with an alpha channel (8-bit alpha for semi-transparent surfaces) to represent the damaged material
A mask for both textures is optional.
Handling the material/texture files
- After you've got your 2 masks and/or textures, place them in the appropriate game/mod materials directory (and whatever subfolders you wish to put them in) (e.g Half-Life 2/hl2/materials).
- Create 2 text documents in the same folder your VTFs are in, with each one sharing a file name with one of your VTF texture files respectively. Make sure you have extensions visible in your computer's file browser, then change the file extension of one text file to .vmt, or save a text document with a .vmt file extension in whatever text editor you're using.
- Note:It's good practice to name your materials (whatever)001a for the first frame then (whatever)001b for the second frame and so on when you are switching between said materials on a brush face(s) in game (in this instance, between an intact and broken material)
The intact texture
After you have created the material/textures in the appropriate paths, copy, paste and fill the "(...)" enclosed strings with the paths to the respective VTF files into your intact material VMT:
"LightmappedGeneric"
{
"$basetexture" "(VTF NAME HERE)"
"$envmap" "env_cubemap"
"$surfaceprop" "(Surface property param goes here, is usually glass)"
"$envmapmask" "(VTF MASK NAME GOES HERE (if used that is, otherwise comment out this line with //))"
"$translucent" 1
"$multipass" 1
"$nocull" 1
"$crackmaterial" "(DAMAGED MATERIAL PATH GOES HERE)"
"LightmappedGeneric_hdr_dx9"
{
"$envmaptint" "[.08 .08 .08]"
}
}
Note:If you are not using a texture mask, comment out (type // behind) the line $envmapmask is on.Insert the appropriate paths where $basetexture, $envmapmask and $crackmaterial are specified
Save the VMT in the same folder as your first (intact) VTF file
The damaged texture
The damaged texture needs to have an alpha channel otherwise skybox/black texture will appear when the surface breaks.
Copy and paste the following code into your damaged material VMT
"ShatteredGlass"
{
$basetexture "(VTF NAME GOES HERE)"
$detail "(VTF NAME GOES HERE)"
$envmap "env_cubemap"
$surfaceprop "(Surface properties goes here, it's glass by default)"
$envmapmask "(TEXTURE MASK GOES HERE (if used, otherwise comment out this line with //))"
$translucent 1
$basetexturetransform "scale .7 .7"
$detailscale 0.7
$unlitfactor 0.0
"ShatteredGlass_DX8"
{
$unlitfactor 0.3
// This is roughly equal to the average value of envmapmask of the unbroken texture
$envmaptint "{201 201 201}"
}
// On the low end, envmaptint + lightmap tint both use the average alpha value
"ShatteredGlass_DX7"
{
// This is roughly equal to the average value of alpha channel of the unbroken basetexture
$lightmaptint "{128 128 128}"
// This is roughly equal to the average value of envmapmask of the unbroken texture
// times the average value of the alpha value of the unbroken base texture
$envmaptint "{100 100 100}"
}
$nocull 1
%notooltexture 1 // hide in texture browser, because it isn't intended to be used directly
"Proxies"
{
"BreakableSurface"
{
}
}
}
Note:If you are not using a texture mask, comment out (type // behind) the line $envmapmask is on.End
Provided you have done everything right, you should now have a texture that works fully with the func_breakable_surf brush entity provided all except 1 side is Nodraw.
Modifications to the other parameters (e.g $lightmaptint) can of course be made without any loss of functionality.