#declare T_Map = // transparency map --
 pigment{
  image_map{ jpeg "Diag_Grid_03.jpg"
             interpolate 2
           } //
          scale 0.135/2
       } // ---------------------------
#declare Opaque_Texture   =
texture{ pigment{ color rgb<1,1,1>*.05}
         finish { phong 0.2 }
       } // ---------------------------
#declare Surface_Material  =
material{
  texture{
    pigment_pattern{ T_Map }
    texture_map{
     [0.0 pigment{rgbf<1,1,1,1>}]
     [1.0 Opaque_Texture  ]
    } // end texture_map
  }// end texture
}// end material ----------------------
box{ <0,0,-0.001>,<1,1,0.001>
     material{ Surface_Material
               scale <1,1,1>*2.45*2
               translate<0,0.1,0>
             } // end material
} // ----------------------------------

#declare T_Map = // transparency map
pigment{
  image_map{ jpeg "Diag_Grid_03.jpg"
             interpolate 2
           } //
  warp{ cylindrical
        orientation 1 dist_exp 1 } //
  scale 0.135
} // ----------------------------------
#declare Opaque_Texture   =
texture{ pigment{color rgb<1,1,1>*1.1}
         finish {phong 0.2 }
       } // ---------------------------
#declare Surface_Material  =
material{
   texture{
      pigment_pattern{ T_Map }
      texture_map{
        [0.0 pigment{rgbf<1,1,1,1>}]
        [0.3 pigment{rgbf<1,1,1,1>}]
        [1.0 Opaque_Texture ]
       } // end texture_map
     }// end texture
  }// end material --------------------
// ------------------------------------
difference{
 cylinder{<0, 0  ,0>,<0,2.0,0>,0.70 }
 cylinder{<0,-0.1,0>,<0,2.1,0>,0.699}
 material{ Surface_Material
           scale <1,4.90,1>
         }//---------------
 rotate<0,30,0>
} // end difference -------------------
// inner cylinder
cylinder{ <0,0,0>,<0,1.77,0>, 0.60
  texture{
   pigment{ color rgb<0.75,0.5,1> }
   finish { phong 0.5 }
         } //
} // end of cylinder ------------------