Thanks,

I've installed v3.7 and the emission term works nicely. Thanks for the advice
too about setting the file gamma to 1.

The only thing I'm struggling with now are the radiosity settings. At first I
had quite blotchy images but I've played around with the settings a bit and have
got a pretty smooth output now. However the brightness across the image is not
perfectly symmetric as it should be. (I'm using Scilab to open up my 16 bit png
files so i can inspect the rgb values carefully)

If anyone has advice on what the problem might be that would be great. I have
attached my code below:

Thanks

Stuart

#local p_start  = 64/image_width;
#local p_end_tune = 8/image_width;
#local p_end_final = 8/image_width;


#local final_eb  = 1.8;
#local final_count = 1600;

global_settings{

assumed_gamma 1.0



radiosity
{
    pretrace_start p_start
    pretrace_end   p_end_final


    count final_count
    low_error_factor .05

    nearest_count 20

    error_bound final_eb


    recursion_limit 1

    minimum_reuse 0.01
    gray_threshold 0.0
    normal on
    }
}


#include "colors.inc"
#include "textures.inc"

#declare h=20; // cylinder height
#declare d=10; // aperture diameter
#declare R=200; // distance of emitting disc to focal plane array (FPA)
#declare ahor=12.8; // width of FPA
#declare aver=ahor/1.33; // height of FPA
#declare e=2; // distance from edge of array to cylinder edge
#declare c=ahor+2*e; // diameter of cylinder
#declare m=(R/(2*h))*(d+ahor)+ahor/2; //radius of emitting disc
#declare p=h/2; // position of camera in front of array
#declare FoVortho =  degrees(2*atan(ahor/(2*p)));       // FoV of orthographic
cam used to view FPA

#declare radianceScene = 5;  // brightness (radiance) of emitting disc
#declare radianceRS = 0;  // brightness (radiance) of emitting cylinder


camera {orthographic location <0,0,p> look_at <0,0,0> angle FoVortho*1.0}

// diffuse slab representing FPA (set no_radiosity with the intention that
reflected rays do not
// get used in the radiosity calculation)
polygon {
    5,
    <-ahor/2,-aver/2,0>, <ahor/2,-aver/2,0>, <ahor/2,aver/2,0>,
<-ahor/2,aver/2,0>, <-ahor/2,-aver/2,0>
    texture {
      finish { emission 0 ambient 0 diffuse 1 specular 0 conserve_energy}
pigment {color rgb<1,1,1>}
    }
    scale 1.0 rotate <0,0,0> no_radiosity
  }

// emitting disc
disc {<0,0,0>,<0,0,2>, m, rotate <0,0,0> translate <0,0,R> pigment {color
rgb<1,1,1>} finish {emission radianceScene ambient 0.0 diffuse 0.0 specular
0.0}}

// cylinder shielding the FPA
cylinder {<0,0,0>,<0,0,h>,c/2 open pigment {color rgb<1,1,1>} finish {emission
radianceRS ambient 0 diffuse 0} }

// disc with hole acting as aperture between scene (the disc) and the FPA
disc {<0,0,h>,<0,0,1>, c/2, d/2 pigment {color rgb<1,1,1>} finish {emission
radianceRS ambient 0 diffuse 0}}

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