// Last edited on 2019-04-10 13:45:19 by stolfilocal

#macro earth_layer_spheroid(r, f)
  // An oblate spheroid with equator on {X,Y} plane
  // equatorial radius {r} and relative polar flattening {f}
  sphere{
    <0,0,0>, r
    scale <1,1,1-f>
  }
#end

#macro earth_layer(rmin, fmin, rmax, fmax, tx)
  // A shell between two oblate spheroids with equatorial
  // radii {rmin,rmax} and relative flattenings {fmin,fmax}
  // at the poles.
  #local shell = 
   #if (rmin > 0)
      difference{
        object{ earth_layer_spheroid(rmax, fmax) }
        object{ earth_layer_spheroid(rmin, fmin) }
      }
    #else
      object{ earth_layer_spheroid(rmax, fmax) }
    #end
  
  #local ang_slice = 30*(rmax - 6000)/6000; // Angle of slice
  #local slibox = box{ <0,0,0>, <10000,10000,10000> } 
  #local slicer = 
    union{
      object{ slibox }
      object{ slibox translate 0.1*z rotate ang_slice*z }
    }
  
  difference{
    object{ shell }
    object{ slicer }
    texture { tx }
  }
#end