cartographer/map_formspec.lua

local TILE_SIZE = 0.25;
local TILE_OFFSET = 0.24; -- Slightly smaller than TILE_SIZE. We overlap tiles slightly to minimize seams

-- NoiseParams table for tile variations
local MAP_NOISE = {
    offset = 0,
    scale = 1,
    spread = {x = 2, y = 2, z = 2},
    seed = minetest.get_mapgen_setting("seed"),
    octaves = 2,
    persist = 0.63,
    lacunarity = 2.0,
    flags = "defaults, absvalue",
};

-- Get the variant of the tile at a given position
-- x: The X position of the tile (in map coordinates)
-- z: The Z position of the tile (in map coordinates)
-- noise: A 2d lookup table of perlin noise. Must contain the position [x + 1][y + 1]
--
-- Returns a number from 1 to 4
local function get_variant(x, z, noise)
    return math.floor(math.min(noise[x + 1][z + 1] * 3, 3)) + 1;
end

local map_formspec_prefix = [[
    formspec_version[3]
    size[%f,%f]
    real_coordinates[true]
    style_type[image_button;border=false]
]];

local tile = "image[%f,%f;%f,%f;%s]";
local marker = "animated_image[%f,%f;%f,%f;;%s;%d;%d]";

-- Generate formspec markup for an unknown biome tile
-- x: The x position of the tile
-- y: The y position of the tile
-- detail: The detail level
-- variant: The tile variant
--
-- Returns a formspec string
local function unknown_biome_tile(x, y, detail, variant)
    return string.format("image[%f,%f;%f,%f;%s.%s.png]",
                         x, y,
                         TILE_SIZE, TILE_SIZE,
                         cartographer.detail_texture(cartographer.skin.unknown_biome_textures, detail),
                         variant);
end

-- Generate formspec markup for a given map
-- data: The mapping data
-- x: The X position of the map (in map coordinates)
-- y: The Z position of the map (in map coordinates)
-- w: The width of the map (in map coordinates)
-- h: The height of the map (in map coordinates)
-- player_x: The X position of the player marker (in map coordinates)
-- player_y: The Y position of the player marker (in map coordinates)
-- detail: The detail level
-- map_scale: Integer scaling factor for displaying a zoomed-out map
-- (Optional) is_visible: Callback to determine if a tile should be drawn
-- (Optional) get_marker: Callback to get the marker for any given tile
-- (Optional) user: userdata passed to the is_visible/get_marker callbacks
--
-- Returns a formspec string
local function generate_map(data, x, y, w, h, player_x, player_y, detail, map_scale, is_visible, get_marker, user)
    local str = "";
    local noise = PerlinNoiseMap(MAP_NOISE, { x=w + 1, y=h + 1, z=1}):get_2d_map({ x=x, y=y});
    player_x = math.floor(player_x / map_scale + 0.5);
    player_y = math.floor(player_y / map_scale + 0.5);

    for i = x,x + w,1 do
        local fx = (i - x) * TILE_OFFSET;
        local column = data.generated[i * map_scale];
        for j = y + h,y,-1 do
            local fy = (y + h - j) * TILE_OFFSET;
            if column == nil or column[j * map_scale] == nil or (is_visible and not is_visible(user, i, j)) then
                str = str .. unknown_biome_tile(fx, fy, detail, get_variant(i - x, j - y, noise));
            else
                local name = minetest.get_biome_name(column[j * map_scale].biome);
                local height = column[j * map_scale].height;
                local biome = cartographer.get_biome_texture(name, math.floor(height + 0.5), detail);

                if biome then
                    local depth = math.min(math.max(math.floor(height / 8), -8), 0) * -1
                    height = math.max(math.min(math.floor(height / 4), 8), 0)

                    local mod = "";
                    if height > 0 then
                        mod = "^[colorize:white:"..tostring(height * 10)
                        height = height * 0.05;

                        str = str .. tile:format(fx, fy - height + TILE_OFFSET, TILE_SIZE, height + 0.01, cartographer.detail_texture(cartographer.skin.cliff_textures, detail)  .. ".png");
                    elseif depth > 0 then
                        mod = "^[colorize:#1f1f34:"..tostring(depth * 10)
                    end

                    str = str..tile:format(fx, fy - height, TILE_SIZE, TILE_SIZE, biome .. "." .. tostring(get_variant(i - x, j - y, noise)) .. ".png" .. mod)

                    if get_marker then
                        local marker = cartographer.get_marker_texture(get_marker(user, i, j), detail);
                        if marker then
                            str = str..tile:format(fx, fy - height, TILE_SIZE, TILE_SIZE, marker .. ".png")
                        end
                    end

                    if i == player_x and j == player_y then
                        local player_icon = cartographer.detail_texture(cartographer.skin.player_icons, detail);
                        str = str..marker:format(fx, fy - height,
                                                 TILE_SIZE, TILE_SIZE,
                                                 player_icon.texture .. ".png",
                                                 player_icon.frame_count,
                                                 player_icon.frame_duration);
                    end
                else
                    str = str .. unknown_biome_tile(fx, fy, detail, get_variant(i - x, j - y, noise));
                end
            end
        end
    end

    return str;
end

-- Get the formspec for a given map segment
-- data: The map data
-- x: The X position of the map, in map coordinates
-- y: The Y position of the map, in map coordinates
-- w: The width of the map, in map coordinates
-- h: The height of the map, in map coordinates
-- detail: The detail level of the map
--
-- Returns a formspec string, the width of the formspec, and the height of the
-- formspec
-- TODO: Remove data argument
function cartographer.get_map_formspec(data, x, y, w, h, detail)
    local formspec_width = (w + 1) * TILE_OFFSET + 0.01;
    local formspec_height = (h + 1) * TILE_OFFSET + 0.01;
    return map_formspec_prefix:format(formspec_width, formspec_height)..generate_map(data, x - (w * 0.5), y - (h * 0.5), w, h, x, y, detail, 1),
           formspec_width,
           formspec_height;
end

-- Get the formspec for a given map table
-- data: The map data
-- map: The map to use
-- x: The X position of the player marker, in map coordinates
-- y: The Y position of the player marker, in map coordinates
--
-- Returns a formspec string, the width of the formspec, and the height of the
-- formspec
-- TODO: Remove data argument
function cartographer.get_map_formspec_map(data, map, x, y) 
    local formspec_width = (map.w + 1) * TILE_OFFSET + 0.01;
    local formspec_height = (map.h + 1) * TILE_OFFSET + 0.01;
    return map_formspec_prefix:format(formspec_width, formspec_height)..generate_map(data, map.x, map.z, map.w, map.h, x, y, map.detail, map.scale, cartographer.is_filled, cartographer.get_marker, map),
           formspec_width,
           formspec_height;
end