Fill Matrix in Spiral Form from center

[Den_vers]

Fill Matrix in Spiral Form from center

I’m working on an island game, the lobby is in the center, but I want the islands that people create to naturally fill up around the lobby, in a grid formation. See the link I posted. Now it was solved, but I don’t know how to translate the c++ code into Roblox, primarily because I don’t understand what they’re doing. How would I fill a matrix in a spiral form from the center?

[nicemike40]

Honestly, the easiest way would be to put a bunch of parts in your workspace, place them how you want, and just manually name them with numbers in order.

Then you can just grab that list:

local spawnPoints = table.sort(workspace.SpawnPoints:GetChildren(), function(a, b) return a.Name < b.Name end)

…and now you have a list of spawn points you can loop through, fill in old ones, whatever. Dead simple, readable, and extendable to more interesting shapes later.

[V_ladzec (Volter)]

are you sure you need this specific algorithm to place your islands?

[Den_vers]

Nice, but there’s a possibility that I might need hundreds of these, and it’s going to be a hassle. I need this algorithm for it, I’m more of a math person.

[V_ladzec (Volter)]

C++

int size = 7;
int matrix[size][size];
int dy[] = { 1,  0, -1, 0 };
int dx[] = { 0, -1,  0, 1 };
int directionCount = 4;

int ringCount = (size - 1) / 2;
int y = ringCount;
int x = ringCount;
int repeatCount = 0;
int value = 1;

matrix[y][x] = value++;
for (int ring = 0; ring < ringCount; ring++)
{
    y--;
    x++;
    repeatCount += 2;
    for (int direction = 0; direction < directionCount; direction++)
        for (int repeat = 0; repeat < repeatCount; repeat++)
        {
            y += dy[direction];
            x += dx[direction];
            matrix[y][x] = value++;
        }
}

Lua code

local size = 7 -- must be an odd integer otherwise there will be no centre in the matrix 
local matrix = {} -- the matrix itself
local delta = {1, 0, -1, 0} -- ive noticed dx is a reverse of dy so we could use one variable for that
local directionCount = 4 -- how many turns to make in one ring

local ringCount = (size - 1) / 2 -- how many rings there are
local y = ringCount
local x = y
local repeatCount = 0 -- how many numbers to add to the matrix on each turn
local value = 0 -- the number that we are going to increment for every position in matrix 

matrix[y] = {}
matrix[y][x] = value
value += 1

for ring = 1, ringCount do
    y += -1
    x += 1
    repeatCount += 2
    for dir = 1, directionCount do
        for rep = 1, repeatCount do
            y = y + delta[dir]
            x = x + delta[directionCount - dir + 1]
            matrix[y] = matrix[y] or {}
            matrix[y][x] = value
            value += 1
        end
    end
end

[Den_vers]

@V_ladzec

local size = 7 -- must be an odd integer otherwise there will be no centre in the matrix 
local matrix = {} -- the matrix itself
local delta = {1, 0, -1, 0} -- ive noticed dx is a reverse of dy so we could use one variable for that
local directionCount = 4 -- how many turns to make in one ring

local ringCount = (size - 1) / 2 -- how many rings there are
local y = ringCount
local x = y
local repeatCount = 0 -- how many numbers to add to the matrix on each turn
local value = 0 -- the number that we are going to increment for every position in matrix 

matrix[y] = {}
matrix[y][x] = value
value += 1
for ring = 0, ringCount do
    y -= 1
    x += 1
    repeatCount += 2
    matrix[y] = {}
    for dir = 0, directionCount do
        for rep = 0, repeatCount do
            y += delta[rep]
            x += delta[RepeatCount - rep]
            matrix[y][x] = value
            value += 1
        end
    end
end

Haha, thanks for this. I was watching you change the script. I’ll test it out, hopefully it’s solid.

[V_ladzec (Volter)]

found some bugs hold on let me fix
im typing from phone so it might take some time

[Den_vers]

I’ll fix the bugs for myself, but if someone else needs this code I guess you can go ahead and that.

[V_ladzec (Volter)]

kind of forgot lua and c++ have different array starting indexes also mistyped some variables
fixed in edit