function GetAngleBeetweenTwoPoints(x1, y1, x2, y2)
  local plus = 0.0
    local mode = 1
    if x1 < x2 and y1 > y2 then plus = math.pi/2; mode = 2; end
    if x1 < x2 and y1 < y2 then plus = math.pi; end
    if x1 > x2 and y1 < y2 then plus = math.pi*1.5; mode = 2; end
    local lx = x2 - x1
    local ly = y2 - y1
    lx = math.abs(lx)
    ly = math.abs(ly)
    if mode == 1 then ly = ly/lx;
    else ly = lx/ly; end
    ly = math.atan(ly)
    ly = ly + plus
    return ly
end