Someone

local circle_cache = {}
local offsetcircle_cache = {}

local function _GetCircle( cx, cy, radius, seg )
	local key = radius .. "/" .. seg
	local key2 = "(" .. cx .. "," .. cy .. ") " .. key
	
	-- did we already calculate the offset of this type of circle?
	if offsetcircle_cache[key2] ~= nil then return offsetcircle_cache[key2] end
	
	-- did we already calculate this type of circle?
	local c = nil
		
	if circle_cache[key] ~= nil then
		c = circle_cache[key]
	else
		c = {}
		
		-- calculate this type of circle.
		local radsperseg = math.rad( 360 / seg )
	
		for i = seg, 1, -1 do
			local r = radsperseg * i - 1
			table.insert( c, { x = math.sin( r ) * radius, y = math.cos( r ) * radius } )
		end
	
		-- cache it for later
		circle_cache[key] = c
	end
	
	local co = {}
	
	-- offset the circle
	for i, v in ipairs( c ) do
		co[i] = {}
		co[i].x = v.x + cx
		co[i].y = v.y + cy
	end
	
	-- cache it
	offsetcircle_cache[key2] = co
	
	return co
end

local function _DrawCircle( cx, cy, r, seg )
	local c = _GetCircle( cx, cy, r, seg )

	surface.DrawPoly( c )
end