Xiaolin Wu's line.lua

-- From Wikipedia @https://en.wikipedia.org/wiki/Xiaolin_Wu's_line_algorithm
-- Xiaolin Wu's line algorithm

local StarterGui = game:GetService("StarterGui")
StarterGui:ClearAllChildren()

local Screen = Instance.new("ScreenGui", StarterGui)

local Triangle = Instance.new("Frame", Screen)
Triangle.BackgroundColor3 = Color3.fromRGB(255, 255, 255)
Triangle.Size = UDim2.new(1, 0, 1, 0)

local Pixel = Instance.new("Frame")
Pixel.BackgroundColor3 = Color3.fromRGB(255, 0, 0)
Pixel.BorderSizePixel = 0
Pixel.Size = UDim2.new(0, 1, 0, 1)

-- Draws a Circle
local function Plot(x, y, Opacity)
	local Point = Pixel:Clone()
	Point.Position = UDim2.new(0, x, 0, y)
	Point.BackgroundTransparency = 1 - Opacity
	Point.Parent = Triangle
end

local abs = math.abs
local floor = math.floor

local function DrawLine(x0, y0, x1, y1)
	local steep = abs(y1 - y0) > abs(x1 - x0)

	if steep then
		x0, y0 = y0, x0
		x1, y1 = y1, x1
	end

	if x0 > x1 then
		x0, x1 = x1, x0
		y0, y1 = y1, y0
	end

	local dx = x1 - x0
	local dy = y1 - y0
	local gradient = dy / dx

	if dx == 0.0 then
		gradient = 1.0
	end

	-- handle first endpoint
	local xend = floor(x0 + 0.5)
	local yend = y0 + gradient * (xend - x0)
	local xgap = 1 - (x0 + 0.5) % 1
	local xpxl1 = xend -- this will be used in the main loop
	local ypxl1 = floor(yend)

	if steep then
		Plot(ypxl1, xpxl1, (1 - yend % 1) * xgap)
		Plot(ypxl1 + 1, xpxl1, yend % 1 * xgap)
	else
		Plot(xpxl1, ypxl1, (1 - yend % 1) * xgap)
		Plot(xpxl1, ypxl1 + 1, yend % 1 * xgap)
	end

	local intery = yend + gradient -- first y-intersection for the main loop

	-- handle second endpoint
	xend = floor(x1 + 0.5)
	yend = y1 + gradient * (xend - x1)
	xgap = (x1 + 0.5) % 1
	local xpxl2 = xend -- this will be used in the main loop
	local ypxl2 = floor(yend)

	if steep then
		Plot(ypxl2 , xpxl2, (1 - yend % 1) * xgap)
		Plot(ypxl2 + 1, xpxl2, yend % 1 * xgap)
	else
		Plot(xpxl2, ypxl2, (1 - yend % 1) * xgap)
		Plot(xpxl2, ypxl2 + 1, yend % 1 * xgap)
	end

	-- main loop
	if steep then
		for x = xpxl1 + 1, xpxl2 - 1 do
			Plot(floor(intery) , x, 1 - intery % 1)
			Plot(floor(intery) + 1, x, intery % 1)
			intery = intery + gradient
		end
	else
		for x = xpxl1 + 1, xpxl2 - 1 do
			Plot(x, floor(intery), 1 - intery % 1)
			Plot(x, floor(intery) + 1, intery % 1)
			intery = intery + gradient
		end
	end
end

local t1 = tick()
DrawLine(200, 200, 600, 600)
print(tick() - t1)