Stormworksでアンチエイリアス付きの多角形を描画する関数

fillPoly.lua

-- 交差判定は以下のコードを利用
-- https://en.wikipedia.org/wiki/Even%E2%80%93odd_rule

-- 通常ver (x2 SS)
function fillPoly(ps, w, h, r, g, b, a)
	a = a and a or 255
	local left, top, right, bottom = w, h, 0, 0
	for i = 1, #ps do
		local v = ps[i]
		left = math.min(math.max(math.floor(v.x), 0), left)
		top = math.min(math.max(math.floor(v.y), 0), top)
		right = math.max(math.min(math.ceil(v.x), w), right)
		bottom = math.max(math.min(math.ceil(v.y), h), bottom)
	end

	for rx = left, right do
		for ry = top, bottom do
			local c = 0
			for x = rx, rx + 0.5, 0.5 do
				for y = ry, ry + 0.5, 0.5 do
					local hit = false
					local j = ps[#ps]
					for ii = 1, #ps do
						local i = ps[ii]
						if ((i.y > y) ~= (j.y > y)) and (x < i.x + (j.x - i.x) * (y - i.y) / (j.y - i.y)) then
							hit = not hit
						end
						j = i
					end
					c = c + (hit and 1 or 0)
				end
			end
			screen.setColor(r, g, b, a * c * 0.25)
			screen.drawRect(rx, ry, 1, 1)
		end
	end
end

-- 綺麗だが少し遅いver (RGSS)
function fillPoly(ps, w, h, r, g, b, a)
	a = a and a or 255
	local left, top, right, bottom = w, h, 0, 0
	for i = 1, #ps do
		local v = ps[i]
		left = math.min(math.max(math.floor(v.x), 0), left)
		top = math.min(math.max(math.floor(v.y), 0), top)
		right = math.max(math.min(math.ceil(v.x), w), right)
		bottom = math.max(math.min(math.ceil(v.y), h), bottom)
	end

	local rad = math.atan(0.5)
	local sin, cos = math.sin(rad), math.cos(rad)
	local pv = math.sqrt(5) * 0.5 * 0.25
	local rg = {
		{ -pv * cos + pv * sin + 0.5, -pv * sin - pv * cos + 0.5 },
		{ pv * cos + pv * sin + 0.5, pv * sin - pv * cos + 0.5 },
		{ pv * cos - pv * sin + 0.5, pv * sin + pv * cos + 0.5 },
		{ -pv * cos - pv * sin + 0.5, -pv * sin + pv * cos + 0.5 }
	}

	for rx = left, right do
		for ry = top, bottom do
			local c = 0
			for pi = 1, #rg do
				local x, y = rx + rg[pi][1], ry + rg[pi][2]
				local hit = false
				local j = ps[#ps]
				for ii = 1, #ps do
					local i = ps[ii]
					if ((i.y > y) ~= (j.y > y)) and (x < i.x + (j.x - i.x) * (y - i.y) / (j.y - i.y)) then
						hit = not hit
					end
					j = i
				end
				c = c + (hit and 1 or 0)
			end
			screen.setColor(r, g, b, a * c * 0.25)
			screen.drawRect(rx, ry, 1, 1)
		end
	end
end