# detector model files
#
#   format as a context free grammar:
#   [line] -> [entry] [comment]
#   [comment] ->
#   [comment] -> #(string comment)
#   [entry] ->
#   [entry] -> [object]
#   [entry] -> [detector]
#   [detector] -> detector (double x) (double y) (double z)
#   [object] -> object [shape] [label] [material name] [density distribution]
#   [shape] -> [sphere]
#   [shape] -> [box]
#   [sphere] -> sphere [shape coords] (double radius)
#   [box] -> box [shape coords] (double dx) (double dy) (double dz)
#   [shape coords] -> (double x) (double y) (double z)
#   [label] -> (string label)
#   [material name] -> (string material)
#   [density distribution] -> [constant]
#   [density distribution] -> [radial polynomial]
#   [constant] -> constant (double density)
#   [radial polynomial] -> radial_polynomial [axis coords] [polynomial]
#   [axis coords] -> (double x) (double y) (double z)
#   [polynomial] -> (int n_params) [polynomial {n_params}]
#   [polynomial {n_params}] -> (double param_n) [polynomial {n_params-1}]
#   [polynomial {1}] -> (double param_1)
#
#   format notes:
#    - no space before first column
#    - delimiter must be whitespaces
#    - for overlapping, objects the object defined later in the file is given precidence
#    - "material name" must be consistent with those defined in the material file
#    - number_of_parameters is the number of params for polynominal density function
#    - parameters : ex.
#       for 3 parameters p0, p1, p2 and distance from Earth's center x :
#       density = p0 + p1*x + p2*x*x
#
#       CAUTION : the unit of density must be [g/cm3] (CGS unit)
#
#    - lines start from '#' or whitespace are treated
#      as comments
#
