./../../../../fig/mpt/modules/geometry/unions/@PolyUnion/feval10.png"> is the cardinality of <tt>indices</tt>.
 
 Note that once the <tt>regions</tt> option is enabled, <tt>PolyUnion/feval()</tt> will not
 perform point location. Instead, it will evaluate the function in all
 polyhedra indexed by <tt>indices</tt>, regardless of whether they contain <tt>x</tt> or
 not.
 
 The <tt>regions</tt> option allows to quickly evaluate multiple functions as
 follows:
 
 <tt>[first_value, idx] = U.feval(x, 'first_funct