cartographer/scanner.lua

local CHUNK_SIZE = _cartographer.CHUNK_SIZE;

local function register_mapchunk(x, y, biome, height)
    if not data.generated[x] then
        data.generated[x] = {
            [y] = {
                biome = biome,
                height = height,
            }
        };
    elseif not data.generated[x][y] or data.generated[x][y].height < height then
        data.generated[x][y] = {
                biome = biome,
                height = height,
            };
    end
end

local function get_mapgen_biome(min, max, mmin, mmax)
    local UNDERGROUND = minetest.get_biome_id("underground");
    local DEFAULT = minetest.get_biome_id("default");

    local biomes = minetest.get_mapgen_object("biomemap");
    local heights = minetest.get_mapgen_object("heightmap");

    local xx = max.x - min.x;
    local yy = max.y - min.y;
    local zz = max.z - min.z;

    local xxx = mmax.x - mmin.x;
    local yyy = mmax.y - mmin.y;
    local zzz = mmax.z - mmin.z;

    local startx = min.x - mmin.x;
    local starty = min.y - mmin.y;
    local startz = min.z - mmin.z;
    
    local scan_biomes = {};
    local scan_heights = {};

    for i = startx,startx + xx,1 do
        for k = startz,startz + zz,1 do
            local b = biomes[i + (k * (xxx + 1))];
            if b ~= nil and b ~= UNDERGROUND and b ~= DEFAULT then
                scan_biomes[b] = (scan_biomes[b] or 0) + 1;
                scan_heights[b] = (scan_heights[b] or 0) + heights[i + (k * (xxx + 1))];
            end
        end
    end

    local biome = nil;
    local high = 0;
    for k,v in pairs(scan_biomes) do
        if v > high then
            biome = k;
            high = v;
        end
    end

    local avg_height = 0;
    if high > 0 then
        avg_height = scan_heights[biome] / high;
    end

    return biome, avg_height;
end

local function get_biome(min, max)
    local UNDERGROUND = minetest.get_biome_id("underground");
    local DEFAULT = minetest.get_biome_id("default");
    local WATER_SOURCE = minetest.registered_aliases["mapgen_water_source"];

    local xx = max.x - min.x;
    local yy = max.y - min.y;
    local zz = max.z - min.z;

    local scan_biomes = {};
    local scan_heights = {};

    for i = min.x,max.x,1 do
        for j = min.y,max.y,1 do
            for k = min.z,max.z,1 do
                local pos = { x=i, y=j, z=k };
                local b = minetest.get_biome_data(pos).biome;
                local node = minetest.get_node(pos).name;
                if b ~= nil and b ~= UNDERGROUND and b ~= DEFAULT and node ~= "air" and node ~= WATER_SOURCE then
                    pos.y = pos.y + 1;
                    node = minetest.get_node(pos).name;
                    if node == "air" or node == WATER_SOURCE then
                        scan_biomes[b] = (scan_biomes[b] or 0) + 1;
                        scan_heights[b] = (scan_heights[b] or 0) + j;
                    end
                end
            end
        end
    end

    local biome = nil;
    local high = 0;
    for k,v in pairs(scan_biomes) do
        if v > high then
            biome = k;
            high = v;
        end
    end

    local avg_height = 0;
    if high > 0 then
        avg_height = scan_heights[biome] / high;
    end

    return biome, avg_height;
end

local function on_generated(min, max, blockseed)
    local chunk = {
        x = tochunk(min.x),
        y = tochunk(min.z),
    };

    for i = tochunk(min.x),tochunk(max.x),1 do
        for j = tochunk(min.z),tochunk(max.z),1 do

            local sub_min = {
                x = i * CHUNK_SIZE,
                y = min.y,
                z = j * CHUNK_SIZE,
            };
            local sub_max = {
                x = i * CHUNK_SIZE + CHUNK_SIZE,
                y = max.y,
                z = j * CHUNK_SIZE + CHUNK_SIZE,
            };
            local biome, height = get_mapgen_biome(sub_min, sub_max, min, max);
            if  biome ~= nil then
                register_mapchunk(i, j, biome, height)
            end

        end
    end
end

function cartographer.queue_region(pos)
    local converted = {
        x = tochunk(pos.x) * CHUNK_SIZE,
        y = tochunk(pos.y) * CHUNK_SIZE,
        z = tochunk(pos.z) * CHUNK_SIZE,
    };

    if data.generated[pos.x] ~= nil and data.generated[pos.x][pos.z] ~= nil then
        return;
    end

    for _,queued_pos in ipairs(cartographer.scan_queue) do
        if vector.equals(converted, queued_pos) then
            return;
        end
    end

    cartographer.scan_queue[#cartographer.scan_queue + 1] = converted;
end

function cartographer.scan_regions()
    local len = #cartographer.scan_queue;

    if len == 0 then
        return;
    end

    local startpos = cartographer.scan_queue[len];
    local endpos = {
        x = startpos.x + CHUNK_SIZE,
        y = startpos.y + CHUNK_SIZE,
        z = startpos.z + CHUNK_SIZE,
    };

    if data.generated[startpos.x] ~= nil and data.generated[startpos.x][startpos.z] ~= nil then
        return;
    end

    local biome,height = get_biome(startpos, endpos);
    if  biome ~= nil then
        register_mapchunk(startpos.x / CHUNK_SIZE, startpos.z / CHUNK_SIZE, biome, height)
    end

    cartographer.scan_queue[len] = nil;
end

minetest.register_on_generated(on_generated);