$detail

$detail specifies a greyscale texture with which Source will add high-resolution detail when the material is viewed up close, by darkening the albedo appropriately.

Syntax

$detail <texture>

You will probably want to use at least $detailscale (see below) as well.

Additional parameters

While the additional $detail params are not strictly required, it is difficult to get good results without them.

$detailscale <float>

Fits the detail texture onto the material the given number of times.

$detailblendmode <int?>

Todo: What are the modes?

$detailblendfactor <float>

Todo: ??

$detailframe <int>

The frame of an animated texture to use. Requires DX9.

$detail_alpha_mask_base_texture <bool?>

Todo: Something to do with masking $basetexture with $detail's alpha channel?

Requires DX9.

Valve's detail textures

Valve's stock detail textures (available in OB only) are best used with the following pre-configured values:

$detail detail/noise_detail_01 // e.g. for brickwork, concrete...
$detailscale 7.74
$detailblendfactor 0.8
$detailblendmode 0

$detail detail\metal_detail_01
$detailscale 4.283
$detailblendfactor .65
$detailblendmode 0

$detail detail\rock_detail_01
$detailscale 11
$detailblendfactor 1
$detailblendmode 0

$detail detail\plaster_detail_01
$detailscale 6.783
$detailblendfactor .8
$detailblendmode 0

There is also detail\wood_detail_01, but not stock material seems to use it.