trails

main.lua

local points = {}
local trails = {}

local N = 100
local w,h = love.graphics.getDimensions()
print(w,h)

local function color(x,y)
	local th = (x+y)/20
	return {(math.cos(th)+1)/2, (math.sin(th)+1)/2, (math.cos(th+math.pi/2+1))/2}
end

local point_mt

local function newpoint(x,y)
	local t = {x=x,y=y}
	setmetatable(t, point_mt)
	return t
end
point_mt = {
	__add = function(a,b)
		return newpoint(a.x+b.x, a.y+b.y)
	end,

	__sub = function(a,b)
		return newpoint(a.x-b[1], a.y-b.y)
	end,

	__mul = function(p,k)
		return newpoint(p.x*k, p.y*k)
	end,

	dist2 = function(a,b)
		return (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y)
	end,

	dist = function(a,b)
		return math.sqrt(a:dist2(b))
	end,
	
	abs = function(a)
		return math.sqrt(a.x*a.x+a.y*a.y)
	end
}; point_mt.__index = point_mt

function love.load()
	for i=1,N do
		points[i] = {
			pos = newpoint(love.math.random(w), love.math.random(h)),
			vel = newpoint(0,0)
		}
	end
end

local mindist = 10

time = 0 
maxtime = 0.5

function love.update(dt)
	time = time + dt

	local mx, my = love.mouse.getPosition()
	for _,p in ipairs(points) do
		if p.pos:dist(newpoint(mx,my)) < mindist then
			p.vel = newpoint(p.pos.x-mx, p.pos.y-my)
		else
			p.vel = p.vel*0.99
		end
		for _,p2 in ipairs(points) do
			if p2 ~= p then
				if p.pos:dist(newpoint(p2.pos.x,p2.pos.y)) < 5 then
					p.vel = newpoint(p.pos.x-p2.pos.x, p.pos.y-p2.pos.y)
					p2.vel = p.vel*-1
				end
			end
		end
		
		table.insert(trails, {birth = time, x = p.pos.x, y = p.pos.y})

		p.pos = p.pos+p.vel+newpoint(math.sin(p.vel.x)*p.vel:abs(), math.sin(p.vel.y)*p.vel:abs())
		p.pos.x = p.pos.x%w
		p.pos.y = p.pos.y%h
	end

	local remove = {}
	for i,t in ipairs(trails) do
		if time - t.birth >= maxtime then
			table.insert(remove, i)
		end
	end
	for k,v in ipairs(remove) do table.remove(trails, v) end
end

function love.draw()
	for i,t in ipairs(trails) do
		local c = color(t.x, t.y)
		c[4] = 1-(time-t.birth)/maxtime
		love.graphics.setColor(c)
		love.graphics.circle("fill", t.x, t.y, 2) 
	end

	for _,p in ipairs(points) do
		love.graphics.setColor(color(p.pos.x, p.pos.y))
		love.graphics.circle("fill", p.pos.x, p.pos.y, 3) 
	end

	love.graphics.circle("line", love.mouse.getX(), love.mouse.getY(), mindist)
end