Cosin graffiti simulator for TIC-80 https://make.echtzeitkultur.org/project/187

graffataq.lua

-- title:   graffataq
-- author:  seism
-- desc:    Make drippy murals inspired by graffiti #CoSin
-- site:    https://make.echtzeitkultur.org/project/187
-- license: MIT License
-- version: 0.3
-- script:  lua

-- References:
-- - Pixel buffer methods and general idea borrowed from PAINT 31 https://tic80.com/play?cart=686
-- - Discussion on simulating brush strokes https://stackoverflow.com/questions/3066820/simulating-brush-strokes-for-painting-application
-- - Discussion on real-time splines https://stackoverflow.com/questions/40948915/spline-with-multiple-durations
-- - Paper with more detail on the above https://people.csail.mit.edu/sarasu/pub/cgim02/cgim02.pdf
-- - Another classic paper on the subject https://www.researchgate.net/publication/220982699_Artistic_brushstroke_representation_and_animation_with_disk_B-spline_curve
-- - WibblyWobbly game code showing how to spline in Lua https://github.com/JettMonstersGoBoom/wibblywobbly/blob/731e4ab30e2c6ca5b4e99cf9ef41f862ecd5bd57/main.lua#L113
-- - A chat log with Qwen3 used to generate a function https://hf.co/chat/r/2nq-EUB?leafId=09892b1b-ca76-46bf-bced-ab48cae3aaf5

local W = 240
local H = 136
local t = 0
local col = 1
local width = 4
local samples_per_segment = 16
local control_points = {}
local needs_help = true

-- The following functions were based on the code in PAINT 31
function draw()
	local pal = 0
	local ini = 0
	for x = 0 + ini, W - 1 do
		for y = 0, H - 1 do
			local c = mget(x, y)
			if c > 0 then
				pix(x, y, c - pal)
			end
		end
	end
end
function OVR()
	poke(0x03FF8, 15)
	cls(0)
	-- updpal(2)
	spr(256, 0, 0, 1, 1, 1, 0, 16, 16)
	spr(256, 128, 0, 1, 1, -1, -1, 16, 16)
	-- spr(256, 120 - 64, 0, -1, 1, 0, 0, 16, 16)
	-- spr(256, 32, 0, -1, 1, 1, 0, 5, 16)
	-- spr(256, 120 + 64, 0, -1, 1, 0, 0, 4, 16)
	draw()
	-- print(string.format("CP: %d", #control_points), 10, 10, 2)
	rect(W - 2, H - 8, 2, 8, col)
	if needs_help then
		print("left click to paint, r-click for new color ->", 3, 129, 12)
	end
end
function SCN()
	--updpal(1)
end
--updpal(2)
sync(0, 0, true)

-- This Catmull-Rom algorith was spit out by Qwen
function evaluate_spline(p0, p1, p2, p3, s)
	local s2 = s * s
	local s3 = s2 * s
	local x = 0.5
		* (
			(-p0.x + 3 * p1.x - 3 * p2.x + p3.x) * s3
			+ (2 * p0.x - 5 * p1.x + 4 * p2.x - p3.x) * s2
			+ (-p0.x + p2.x) * s
			+ 2 * p1.x
		)
	local y = 0.5
		* (
			(-p0.y + 3 * p1.y - 3 * p2.y + p3.y) * s3
			+ (2 * p0.y - 5 * p1.y + 4 * p2.y - p3.y) * s2
			+ (-p0.y + p2.y) * s
			+ 2 * p1.y
		)
	return { x = x, y = y }
end

function round(r)
	return math.floor(r + 0.5)
end

function brush(x, y, size)
	for i = round(y - size / 2), round(y + size / 2) do
		mset(x, i, col)
	end
end

function swipe(x, y)
	if #control_points == 4 then
		table.remove(control_points, 1)
	end
	table.insert(control_points, { x = x, y = y })

	if #control_points == 4 then
		-- Get neighboring control points for the current segment
		local p0 = control_points[1]
		local p1 = control_points[2]
		local p2 = control_points[3]
		local p3 = control_points[4]
		for j = 0, samples_per_segment do
			local i = j / samples_per_segment
			local position = evaluate_spline(p0, p1, p2, p3, i)
			local xx = position.x
			local yy = position.y
			local ww = width
			-- Make drips once in a while
			if math.random() < 0.005 then
				ww = ww * round(math.random() * 10)
				yy = yy + round(ww / 2)
			end
			brush(xx, yy, ww)
		end
	end
end

function dibujarlite()
	local x, y, l, m, r = mouse()
	if l or m or r then
		-- First click
		needs_help = false
	end

	if x < W and x > 0 and y < H and y > 0 then
		if l then
			-- Start swiping
			swipe(x, y)
		end
		if m then
			-- Just a dab
			brush(x, y, width)
		end
	end

	if r and t % 2 == 0 then
		-- Change color
		col = col + 1
		if col > 14 then
			col = 1
		end
		-- Reset the brush
		control_points = {}
	end
end

cls(13)

function TIC()
	dibujarlite()
	t = t + 1
end