I see that you got it working. Did you have to modify the mi file much or did it work as is, gui declaration and all?
I did make the mi file until I saw you had it working using one from another website!
Here what I had!
Code:
#----------------------------------------------------------------------------
#
# Daniel Rind's Diffusion Mental Ray shader MI declarations
#
#----------------------------------------------------------------------------
$ifndef "Diffusion"
set "Diffusion" "true"
declare shader
color "Diffusion" (
color "surface" default 0.9 0.8 0.7,
color "absorption" default 0.6 0.2 0.1,
scalar "diffusion" default 0.1,
scalar "intensity" default 1.0,
integer "samples" default 8,
scalar "direct" default 0.5,
scalar "indirect" default 0.5,
boolean "textured_scatter" default off,
scalar "scatter" default 1.0 1.0 1.0,
boolean "use_irradiance" default false,
color "radiance" default 0.7 0.7 0.7,
integer "area_samples" default 0,
color "illum" default 0.0 0.0 0.0,
scalar "illum_amount" default 0.5,
scalar "spread" default 1.0,
scalar "IOR" default 1.5,
scalar "refractiveness" default 0.0,
array light "lights"
)
version 1
apply material
end declare
$endif