BodyList = {}
Body = class(nil,{type=0})

function newBody(data)
	local o = {}
	-- coordinates
	o.x = data.pos[1] or 0
	o.y = data.pos[2] or 0
	o.z = data.pos[3] or 0
	-- velocities
	o.vx = data.vel[1] or 0
	o.vy = data.vel[2] or 0
	o.vz = data.vel[3] or 0
	-- accceleration
	o.ax = 0
	o.ay = 0
	o.az = 0
	-- mass
	o.mass = data.mass or 1
	-- size
	o.size = data.size or VIEW.planet_size*math.sqrt(data.mass)
	-- color
	o.color = data.color or {1,1,1}
	o.max_distance = 0
	-- origin
	o.origin = data.origin or nil
	table.insert(BodyList,o)
end

function UpdateBodiesAcceleration()
  for n, body in pairs(BodyList) do
    local ax = 0
    local ay = 0
    local az = 0
    for o_n, other_body in pairs(BodyList) do
      if n ~= o_n then

        local dx = other_body.x - body.x
        local dy = other_body.y - body.y
        local dz = other_body.z - body.z

        local d3 = dx*dx + dy*dy + dz*dz
        if math.sqrt(d3)/3 > body.max_distance then body.max_distance = math.sqrt(d3)/3 end

        local f =
          (CONST_G * other_body.mass) /
          d3 * math.sqrt(d3 + CONST_S)

        ax = ax + dx * f
        ay = ay + dy * f
        az = az + dz * f
      end
    end

    body.ax = ax
    body.ay = ay
    body.az = az
  end
end

function UpdateBodiesVelocity(dt)
  for _, body in pairs(BodyList) do
    body.vx = body.vx + body.ax * dt
    body.vy = body.vy + body.ay * dt
    body.vz = body.vz + body.az * dt
  end
end

function UpdateBodiesPosition(dt)
  for _, body in pairs(BodyList) do
    body.x = body.x + body.vx * dt
    body.y = body.y + body.vy * dt
    body.z = body.z + body.vz * dt
  end
end