global_settings{ 

  max_trace_level 30
  assumed_gamma 1.0
  photons {
      spacing 0.02
    }
}       

// radiosity (global illumination) settings
#declare rad_on = 0;
#if (rad_on = 1)
#default{ finish{ ambient 0 diffuse 1 }} 

global_settings {
  radiosity {
    pretrace_start 0.08           // start pretrace at this size
    pretrace_end   0.04           // end pretrace at this size
    count 200                      // higher -> higher quality (1..1600) [35]

    nearest_count 5               // higher -> higher quality (1..10) [5]
    error_bound 1.8               // higher -> smoother, less accurate [1.8]
    recursion_limit 3             // how much interreflections are calculated (1..5+) [3]

    low_error_factor .5           // reduce error_bound during last pretrace step
    gray_threshold 0.0            // increase for weakening colors (0..1) [0]
    minimum_reuse 0.015           // reuse of old radiosity samples [0.015]
    brightness 1                  // brightness of radiosity effects (0..1) [1]

    adc_bailout 0.01/2
  }
}
#end
         
#declare enable_dof = 0;         
         
#declare Camera_0 = // front view
camera
{
    perspective angle 90
    location  <3.0 , 1.5 ,-3.0>
    right     x*image_width/image_height
    look_at   <1.3 , 1.0 , 4.0>
    #if (enable_dof = 1)
        focal_point <2.4, 1, .2> blur_samples 20 aperture 0.14 
    #end
}                             
camera { Camera_0 }

light_source
{
    <1.25,0.25,-1.0>
    color rgb 0.4 
    spotlight
    point_at <4, 0.5, 4>  
    //looks_like { sphere { 0*x, 0.1 pigment { rgb <1,1,0> } } } 
    photons {           // photon block for a light source
        refraction on
        reflection on
    } 
    
}           

merge
{
    union
    {                 
        plane { y, 0 }
        plane { y, 2 }
        plane { x, 0 }
        plane { x, 4 }
        plane { z, 4 } 
        
    }                                 
    //box { <-0.001,-0.001,-0.001>, <4.001,2.001,4.001> inverse }    
    pigment { rgb 1 }
    finish
    {
        specular 0.1
        //reflection { 0.01 }
    }
}       
union
{
    prism
    {
        0,1.5,4
        <-1,0>
        <1, 0>
        <0, 2>
        <-1,0> 
        translate <2.2,0.01,0.2>
        scale 0.5
        scale 1.6*x
        scale 1.6*z
        rotate y*3
    }
         /*
    intersection
    {                            
        sphere { <3,0.5,3>, 0.3 }
        sphere { <3.1,0.5,3.1>, 0.3 }
    }  */  
        
    pigment { rgbf <1,1,1,1> }
    //pigment { rgb <1,0,0> }
    finish
    {
        diffuse .6
        ambient 0.1
        specular 0.1   
        phong 0.4
        reflection { 0.3 }
        
    }
    interior
    {   
        ior 1.6 
        fade_power 1001
        fade_distance 0.9
        fade_color 0.7 
        dispersion 1.2
    }   
    photons
    {  //photon block for an object
        target 1.0
        refraction on
        reflection on
    }
}