lua-test/lua-test/main.lua

local fov = 90 * math.pi / 180

local playerx = 10
local playery = 10
local angle = 0

local playerspeed = 0
local playerswspeed = 0
local playermaxspeed = 100

function love.load()
	love.mouse.setRelativeMode(true)
end

function love.mousemoved(x, y, dx, dy)
	angle = angle - dx / love.graphics.getWidth() * 2 * math.pi
end

function love.update(dt)
	playerx = playerx + math.sin(angle) * playerspeed * dt
	playerx = playerx + math.cos(angle) * playerswspeed * dt
	playery = playery + math.cos(angle) * playerspeed * dt
	playery = playery - math.sin(angle) * playerswspeed * dt
end

function love.keypressed(key)
	if key == 'w' then
		playerspeed = playerspeed + playermaxspeed
	elseif key == 's' then
		playerspeed = playerspeed - playermaxspeed
	elseif key == 'a' then
		playerswspeed = playerswspeed + playermaxspeed
	elseif key == 'd' then
		playerswspeed = playerswspeed - playermaxspeed
	elseif key == 'o' then
		fov = fov + 10 * math.pi / 180
	elseif key == 'p' then
		fov = fov - 10 * math.pi / 180
	elseif key == 'q' then
		love.event.quit()
	end
end

function love.keyreleased(key)
	if key == 'w' then
		playerspeed = playerspeed - playermaxspeed
	elseif key == 's' then
		playerspeed = playerspeed + playermaxspeed
	elseif key == 'a' then
		playerswspeed = playerswspeed - playermaxspeed
	elseif key == 'd' then
		playerswspeed = playerswspeed + playermaxspeed
	end
end

function transform(wx, wy)
	-- Player-relative space (translation)
	local tx = wx - playerx
	local ty = wy - playery

	-- Player-relative space (rotation)
	local rx = math.cos(angle) * tx - math.sin(angle) * ty
	local ry = math.cos(angle) * ty + math.sin(angle) * tx

	-- -1.0 to +1.0 abstract screen space (perspective)
	-- Player-relative x maps to *-x*
	-- Player-relative y maps to *z*
	local px = -rx / ry / math.tan(fov / 2)

	-- Screen space (scaling and translation)
	local hwidth = love.graphics.getWidth() / 2
	local x = px * hwidth + hwidth
	local z = ry

	return x, z
end

function drawWall(wx1, wy1, wx2, wy2)
	local hwidth = love.graphics.getWidth() / 2
	local hheight = love.graphics.getHeight() / 2
	local x1, z1 = transform(wx1, wy1)
	local x2, z2 = transform(wx2, wy2)

	if z1 < 0 and z2 < 0 then
		love.graphics.setColor(0.8, 0.7, 0.7)
		love.graphics.line(wx1 + hwidth, wy1 + hheight, wx2 + hwidth, wy2 + hheight)
		-- Fully outside of viewport, don't bother
		return
	end

	love.graphics.setColor(1, 0, 0)
	love.graphics.line(wx1 + hwidth, wy1 + hheight, wx2 + hwidth, wy2 + hheight)

	if z1 < 0 or z2 < 0 then
		local clippingx = playerx + 0.001*math.sin(angle)
		local clippingy = playery + 0.001*math.cos(angle)

		local x = nil
		local y = nil

		if wx2 ~= wx1 then
			local clippingslope = -math.sin(angle)/math.cos(angle)
			local wallslope = (wy2 - wy1)/(wx2 - wx1)
			x = (-clippingslope*clippingx + clippingy + wallslope*wx1 - wy1)/(wallslope - clippingslope)
			y = wallslope*(x - wx1) + wy1
		else
			local perclippingslope = -math.cos(angle)/math.sin(angle)
			local perwallslope = (wx2 - wx1)/(wy2 - wy1)
			y = (-perclippingslope*clippingy + clippingx + perwallslope*wy1 - wx1)/(perwallslope - perclippingslope)
			x = perwallslope*(y - wy1) + wx1
		end

		if z1 < 0 then
			x1, z1 = transform(x, y)
			love.graphics.setColor(0.8, 0.5, 0.5)
			love.graphics.line(wx1 + hwidth, wy1 + hheight, x + hwidth, y + hheight)
		else
			x2, z2 = transform(x, y)
			love.graphics.setColor(0.8, 0.5, 0.5)
			love.graphics.line(x + hwidth, y + hheight, wx2 + hwidth, wy2 + hheight)
		end
	end

	local wall1 = hwidth * 60 / z1 / math.tan(fov / 2)
	local wall2 = hwidth * 60 / z2 / math.tan(fov / 2)

	love.graphics.setColor(1, 1, 1)
	love.graphics.line(x1, hheight - wall1, x2, hheight - wall2)
	love.graphics.line(x1, hheight + wall1, x2, hheight + wall2)
	love.graphics.line(x1, hheight - wall1, x1, hheight + wall1)
	love.graphics.line(x2, hheight - wall2, x2, hheight + wall2)

	if z1 < 0 then
		love.graphics.setColor(0, 0, 1)
		square = {
			wx1 - 5 + hwidth, wy1 - 5 + hheight,
			wx1 + 5 + hwidth, wy1 - 5 + hheight,
			wx1 + 5 + hwidth, wy1 + 5 + hheight,
			wx1 - 5 + hwidth, wy1 + 5 + hheight,
		}
		love.graphics.polygon('fill', square)
		love.graphics.line(hwidth+playerx, hheight+playery, hwidth+wx1, hheight+wy1)
	end
	if z2 < 0 then
		love.graphics.setColor(0, 0, 1)
		square = {
			wx2 - 5 + hwidth, wy2 - 5 + hheight,
			wx2 + 5 + hwidth, wy2 - 5 + hheight,
			wx2 + 5 + hwidth, wy2 + 5 + hheight,
			wx2 - 5 + hwidth, wy2 + 5 + hheight,
		}
		love.graphics.polygon('fill', square)
		love.graphics.line(hwidth+playerx, hheight+playery, hwidth+wx2, hheight+wy2)
	end
end

function love.draw()
	local hwidth = love.graphics.getWidth() / 2
	local hheight = love.graphics.getHeight() / 2

	drawWall(-300, -200, -200, 100)
	drawWall(-150, 200, 300, 200)
	drawWall(300, 200, 300, -200)
	drawWall(300, -200, -300, -200)

	love.graphics.setColor(0, 1, 0)
	love.graphics.line(hwidth+playerx, hheight+playery, hwidth+playerx + math.sin(angle + fov/2) * 5, hheight+playery + math.cos(angle + fov/2) * 5)
	love.graphics.line(hwidth+playerx, hheight+playery, hwidth+playerx + math.sin(angle - fov/2) * 5, hheight+playery + math.cos(angle - fov/2) * 5)
end