/* A plano element */
                    
#declare ThisOrigin = NextOrigin;
//#declare Plano =  intersection { cylinder {  z*0,z*Thk,    100 material { Lensopen }        } 
//                                 cylinder { -z*1,z*(Thk+1),D1  texture  { Lensblnk } hollow }
//                               }  

#declare NextOrigin = ThisOrigin + Thk + Nex;
               
#declare Plano = cylinder {  z*0,z*Thk,D1 material { Lensopen } }