$desaturatewithbasealpha


... 

$desaturatewithbasealpha
is a material shader parameter available in all Source games since
Alien Swarm for
VertexLitGeneric
.
Setting it to a value above 0
will enable the behavior.
If used, the $basetexture
's Alpha channel will be used as a mask to de-saturate the $basetexture
's Color.
The amount of desaturation is determined through the same parameter. 1.0
will result in 100%, and 0.5
in 50% desaturation.




Caveats

$seamless_base
. (this works in)
$detail
. (this works in)
$bumpmap
or any parameters that requires a$bumpmap
. Including$lightwarptexture
. (this works in)
$selfillum
and thus $selfillummask (this works in)
$selfillum_envmapmask_alpha
. (this works in)
$basealphaenvmapmask
. (this works in)
