Simple scrolling "mountain range" for Löve2d

train.lua

local train = {}
train.__index = train

local lg, lm = love.graphics, love.math

local MAXY = 1000

-- We use the previous value so that it doesn't get too crazy looking
-- Will need better generation which min and max so it doesn't go up or down forever 
local function generateValue(previous) return (lm.random(20)-10)*2+previous*0.25 end

local function addBase(tbl, back)
	table.insert(tbl, back)
	table.insert(tbl, MAXY)
	table.insert(tbl, tbl[1]) --Get the current X of the front
	table.insert(tbl, MAXY)
end

local function removeBase(tbl)
	for i = 1, 4 do table.remove(tbl, #tbl) end --Remove the last 4 values
end

-- Generates a line with different Y values which moves towards the right
-- train:new(200, 10, 20)
function train:new(length, peaks, speed)
	local o = {}
	setmetatable(o, self)
	
	o.length = length or error("Train requires length")
	peaks = peaks or error("Train requires peaks")
	o.speed = speed or error("Train requires speed")
	o.deltaX = 0
	o.distance = length / peaks
	o.distanceTraveled = o.distance -- So that we have 1 vertex that extends past the distance
	
	o.vertices = {}
	
	local previousValue = 0
	
	for i = -o.distance, length+o.distance*2, o.distance do
		table.insert(o.vertices, i) --X
		previousValue = generateValue(previousValue)
		table.insert(o.vertices, previousValue) --Y
	end
	
	addBase(o.vertices, length+o.distance)
	
	--Make triangles due to shape being concave for fill draw
	o.triangles = lm.triangulate(o.vertices)
	
	return o
end

function train:update(dt)
	self.deltaX = self.deltaX + self.speed * dt
	if self.deltaX >= self.distanceTraveled then
		self.distanceTraveled = self.distanceTraveled + self.distance
		for i = 1, 2 do table.remove(self.vertices, 1) end --Remove the Front
		removeBase(self.vertices) --Remove base to allow new values
		--Add new back
		table.insert(self.vertices, self.length + self.distanceTraveled)
		table.insert(self.vertices, generateValue(self.vertices[#self.vertices-1])) -- -1 here will get the previous vertex Y
		--Add base back
		addBase(self.vertices, self.length+self.distanceTraveled)
		
		self.triangles = lm.triangulate(self.vertices) 
	end
end

function train:draw(x, y, mode)
	mode = mode or "fill"
	lg.push()
	lg.translate(x - self.deltaX, y)
	if mode == "fill" then --Fill cannot draw our concave shape so it has to use triangles
		for _, v in ipairs(self.triangles) do
			lg.polygon(mode, v)
		end
	else
		lg.polygon("line", self.vertices) --Line can handle the concave shape
	end
	lg.pop()
end

return train

Gif Preview