def density
        if (@density.is_a?Density)
          return @density
        end
        rerolls=(1..@size).to_a.select { |r| @reroll_modifiers.any? { |m| mod.reroll_with? r } }
        if(@compounding)
          temp=CompoundDieDensity.new(@size,rerolls)
          @density=ModifiedDieDensity.new(temp,@count,@fun_modifiers)
        elsif(@penetrating)
          temp=PenetratingDieDensity.new(@size,rerolls)
          @density=ModifiedDieDensity.new(temp,@count,@fun_modifiers)
        # This is a rather special case....
        elsif(@exploding)
          nomaxrolls=rerolls
          if (not rerolls.include? @size)
            nomaxrolls << @size
          end
          temp=DieDensity.new(@size,nomaxrolls)
          count=ExplodingDieNumberDensity.new(@size,rerolls,@count)

          if (rerolls.include? @size)
            @density=ModifiedDieDensity.new(temp,@count,@fun_modifiers)
          else
            @density=ExplodingDieDensity.new(temp,@size,@count,@fun_modifiers)
          end
        else
          temp=DieDensity.new(@size,rerolls)
          @density=ModifiedDieDensity.new(temp,@count,@fun_modifiers)
        end
        return @density
      end