#declare canvas = union {   
  object{#include "main_canvas.msh"} 
  object{#include "front_canvas.msh"}
  object{#include "front_canvas.msh" translate -12*x} 
  
  texture {
     pigment {color rgb <1,1,.9>}
     normal  {bumps .1 scale .5}
  }  
  
}