Op 20/01/2024 om 17:14 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> 
>> I have no access presently to the PC where I have stored my stuff (and
>> it is some years since last I used backside illumination). First thing
>> in the morning, on my ToDo. Sorry for the delay!
> 
> Never fear, intrepid renderer - I figgered it out.
> 
> I just needed to add the ft values in, using a constant function in the pigment
> map.
> 
> So, it works, but probably could use a fair bit of improvement.
> 
> - BW
> 
Excellent!

Just in case you want to play with those diffuse parameters, here is 
some code (+ an image map) I used a long time ago in my window scene 
with the Sultana (Gancaloon Project):

//==================================================
#declare p_curtain_1 = pigment {image_map {png 
"Orange_Gold_Damask_by_R2krw9.png" gamma srgb interpolate 2 filter all 0.5}}
#declare p_curtain_2 = pigment {image_map {png 
"Orange_Gold_Damask_by_R2krw9.png" gamma srgb interpolate 2 filter all 0.0}}
#declare p_curtain_sat = pigment {image_map {png 
"Orange_Gold_Damask_by_R2krw9_sat.png" gamma 1 interpolate 2}}

//==================================================
//Material definitions
#declare Curtain_=
#declare f_curtain_1 =
finish {
   specular 0.0
   roughness 0.0005
   diffuse 0.8, 0.2  //using backside illumination
   conserve_energy
}

#declare f_curtain_2 =
finish {
   specular 0.25
   roughness 0.002
   diffuse 0.8, 0.3  //using backside illumination
   conserve_energy
}

material {
   texture {uv_mapping
     pigment_pattern {p_curtain_sat}
     texture_map {
       [0.0 pigment {p_curtain_1}
            finish {f_curtain_1}
       ]
       [1.0 pigment {p_curtain_2}
            finish {f_curtain_2}
       ]
     }
   }
}
//==================================================

-- 
Thomas

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