noita-mapcap/files/libraries/hilbert-curve.lua

66 lines
1.2 KiB
Lua

-- Copyright (c) 2019-2022 David Vogel
--
-- This software is released under the MIT License.
-- https://opensource.org/licenses/MIT
---@class HilbertLib
local Hilbert = {}
---Rotate/flip quadrant.
---@param n integer
---@param x integer
---@param y integer
---@param rx boolean
---@param ry boolean
---@return integer
---@return integer
local function hilbertRotate(n, x, y, rx, ry)
if not ry then
if rx then
x = n - 1 - x
y = n - 1 - y
end
x, y = y, x
end
return x, y
end
---Maps t in the range of [0, (2^potSize)^2-1] to a position on the hilbert curve with the side length of 2^potSize (Power of two size).
---@param t integer
---@param potSize integer
---@return integer
---@return integer
function Hilbert.Map(t, potSize)
local size = math.pow(2, potSize)
local x, y = 0, 0
if t < 0 or t >= size * size then
error("variable t is outside of the range")
end
for i = 0, potSize - 1, 1 do
local iPOT = math.pow(2, i)
local rx = bit.band(t, 2) == 2
local ry = bit.band(t, 1) == 1
if rx then
ry = not ry
end
x, y = hilbertRotate(iPOT, x, y, rx, ry)
if rx then
x = x + iPOT
end
if ry then
y = y + iPOT
end
t = math.floor(t / 4)
end
return x, y
end
return Hilbert