//-------------------------------------------------------------------------------------------------
//-------------------------------------------------------------------------------------------------
#declare Pigment_1 = 
  pigment {
    crackle 
    color_map{
      [0.00, rgb <1,0.60,0.60> ]
      [0.15, rgb <1,1,1>*0.8 ]
      [1.00, rgb <1,1,1>*0.78 ]
    }
 scale 0.25
 } // end pigment

#declare Crack= function {
  pigment {    
     Pigment_1
  } // end pigment
}
#declare R= function(u,v) {
  -Crack(u,v,0).gray *1.5
}
//-------------------------------------------------------------------------------------------------
#declare F1=function(u,v){R(u,v)*(cos(u)+v*cos(u/2)*cos(u))}
#declare F2=function(u,v){R(u,v)*(sin(u)+v*cos(u/2)*sin(u))}
#declare F3=function(u,v){v*sin(u/2)}              
//-------------------------------------------------------------------------------------------------
#include "meshmaker.inc"
//-------------------------------------------------------------------------------------------------
object{ // Parametric(Fx,Fy, Fz, <UVmin>, <UVmax>, Iter_U, Iter_V, FileName)
   Parametric( // Builds a parametric surface out of three given functions. 
               // The uv_coordinates for texturing the surface come from the square <0,0> - <1,1>. 
      F1, F2, F3, //three functions
      <0, -0.5>, <2*pi, 0.5>,// range within to calculate surface: <u min, v min>,<u max, v max>. 
      250, 500, // resolution of the mesh in the u range and v range.
       "" // FileName: ""= non, "NAME.obj'= Wavefront objectfile, "NAME.pcm" compressed mesh file 
          // "NAME.arr" = include file with arrays to build a mesh2 from, 
          //  others: includefile with a mesh2 object 
   ) //---------------------------------------------------------------------------------------------
 //  no_shadow
   interior_texture {  //  outside texture
    // uv_mapping
     pigment{  color rgb <1,1,1> }
     finish { specular 0.5}
   } // 
   texture{            // inside texture
   //  uv_mapping
     pigment{ color  rgb <1,1,1> }
     finish { phong 0.5 }
   } // 
   
   rotate<90,0,0>
   scale<-1,1,1>*1
   translate< 0, 0, 0 >
} // end of object 
//---------------------------------------------------------------------------------------------------
//---------------------------------------------------------------------------------------------------