Save biome size in separate variable

Currently, performance seems an issue - the cause of the effects is to be determined.

API.md

@@ -100,4 +100,63 @@ The shapes are defined as follows:
 Just like the surface world, the underground world uses biomes to decorate their
 caves. The cave biomes are independent of the cave shapes.
 
-**Under development.**
+For shapes, the following functions are available:
+
+- `noordstar_caves.register_biome(biome def)` Define a new cave biome
+- `noordstar_caves.unregister_biome(name)` Remove a defined cave biome
+- `noordstar_caves.clear_registered_biomes()` Remove all known cave biomes
+
+The biomes are defined as follows:
+
+```lua
+{
+    name = "noordstar_caves:tundra",
+    -- Unique name identifying the biome
+    -- Namespacing is not required but recommended
+
+    node_dust = "foo:snow",
+    -- Node dropped onto floor after all else is generated
+
+    node_floor = "foo:dirt_with_snow",
+    -- Node forming the floor that the player walks on
+
+    node_wall = "foo:ice",
+    -- Node forming the side walls of the cave
+
+    node_roof = "foo:bluestone",
+    -- Node forming the ceiling of the cave
+
+    node_air = "foo:air",
+    -- Nodes filling the inside of the cave. By default, this is air.
+    -- You can replace it with e.g. water to make the entire cave a water cave.
+    -- Keep in mind that cave biomes can blend, so it might not always look
+    -- very smooth.
+
+    node_shell = "foo:permafrost",
+    depth_shell = 3,
+    -- Node forming a layer around the entire cave and thickness of this layer
+    -- You can make the depth as high as you want, but raising it past 16
+    -- might cause hard cut-offs at chunk edges.
+
+    y_max = -100,
+    y_min = -31000,
+    -- Upper and lower limits of the cave biome.
+    -- Alternatively you can use xyz limits as shown below.
+
+    max_pos = { x =  31000, y = -100, z =  31000 }
+    min_pos = { x = -31000, y = -500, z = -31000 }
+    -- xyz limits for biome, an alternative to using `y_min` and `y_max`.
+    -- Cave biome is limited to a cuboid defined by these positions.
+    -- Any x, y or z field left undefined defaults to -31000 in `min_pos` or
+    -- 31000 in `max_pos`.
+
+    heat_point = 0,
+    humidity_point = 50,
+    -- Characteristic temperature and humidity for the biome.
+    -- Just like the Minetest Lua API for biomes, these values create
+    -- 'biome points' on a voronoi diagram with heat and humidity as axes.
+    -- The resulting voronoi cells determine the distribution of the biomes.
+    -- Heat and humidity have an average of 50, vary mostly between 0 and 100
+    -- but can exceed these values.
+}
+```

init.lua

@@ -11,6 +11,9 @@ noordstar_caves = {}
 -- Load features to influence cave shapes
 load("shape")
 
+-- Load features to influence cave biomes
+load("biome")
+
 -- Start engine to generate caves
 load("engine")
 

lua/biome.lua

@@ -0,0 +1,91 @@
+-- This file takes care of cave biomes
+
+noordstar_caves.registered_biomes = {}
+
+-- Clean the input and return a valid shape def
+-- If the input is invalid, return nil
+local function clean_def(def)
+    if type(def.name) ~= "string" then
+        return nil
+    end
+    if type(def.heat_point) ~= "number" then
+        return nil
+    end
+    if type(def.humidity_point) ~= "number" then
+        return nil
+    end
+
+    local d = {
+        name = def.name,
+        heat_point = def.heat_point,
+        humidity_point = def.humidity_point,
+    }
+
+    -- Position
+    if type(def.min_pos) == "table" then
+        d.minp = {
+            x = def.min_pos.x or -1e5,
+            y = def.min_pos.y or -1e5,
+            z = def.min_pos.z or -1e5,
+        }
+    elseif type(def.y_min) == "number" then
+        d.minp = { x = -1e5, y = def.y_min, z = -1e5 }
+    else
+        d.minp = { x = -1e5, y = -1e5, z = -1e5 }
+    end
+
+    if type(def.max_pos) == "table" then
+        d.maxp = {
+            x = def.max_pos.x or 1e5,
+            y = def.max_pos.y or 1e5,
+            z = def.max_pos.z or 1e5,
+        }
+    elseif type(def.y_max) == "number" then
+        d.maxp = { x = 1e5, y = def.y_max, z = 1e5 }
+    else
+        d.maxp = { x = 1e5, y = 1e5, z = 1e5 }
+    end
+
+    -- Optional nodes
+    if type(def.node_dust) == "string" then
+        d.node_dust = def.node_dust
+    end
+    if type(def.node_floor) == "string" then
+        d.node_floor = def.node_floor
+    end
+    if type(def.node_wall) == "string" then
+        d.node_wall = def.node_wall
+    end
+    if type(def.node_roof) == "string" then
+        d.node_roof = def.node_roof
+    end
+    if type(def.node_air) == "string" then
+        d.node_air = def.node_air
+    end
+    if type(def.node_shell) == "string" then
+        d.node_shell = def.node_shell
+    end
+    if type(def.depth_shell) == "number" then
+        d.depth_shell = def.depth_shell
+    else
+        d.depth_shell = 0
+    end
+
+    return d
+end
+
+function noordstar_caves.register_biome(def)
+    local d = clean_def(def)
+
+    if d ~= nil then
+        noordstar_caves.registered_biomes[d.name] = d
+    end
+end
+
+function noordstar_caves.unregister_biome(name)
+    noordstar_caves.registered_biomes[name] = nil
+end
+
+function noordstar_caves.clear_registered_biomes()
+    noordstar_caves.registered_biomes = {}
+end

lua/engine.lua

@@ -2,6 +2,41 @@
 -- Constants and magic numbers
 local mapgen_buffer = 16
 
+-- Cave biome range
+local biome_spread_range = 50
+
+-- Noise params for heat_point
+local heat_noise_params =
+    { offset = 50
+    , scale = 50
+    , spread = { x = biome_spread_range, y = biome_spread_range, z = biome_spread_range }
+    , seed = 320523
+    , octaves = 2
+    , persistence = 0.1
+    , lacunarity = 2.0
+    , flags = ""
+    }
+
+-- Noise params for humidity_point
+local humidity_noise_params =
+    { offset = 50
+    , scale = 50
+    , spread = { x = biome_spread_range, y = biome_spread_range, z = biome_spread_range }
+    , seed = 9923473
+    , octaves = 2
+    , persistence = 0.1
+    , lacunarity = 2.0
+    , flags = ""
+    }
+
+local default_biome =
+    { name = "noordstar_caves:none"
+    , heat_point = -1e6
+    , humidity_point = -1e6
+    , minp = { x = -1e5, y = -1e5, z = -1e5 }
+    , maxp = { x =  1e5, y =  1e5, z =  1e5 }
+    }
+
 -- Convert 3d relative coordinates to an index on a flat array
 local function from_3d_to_flat(dx, dy, dz, nx, ny)
     return (nx * ny * dz) + (nx * dy) + dx + 1
@@ -421,6 +456,46 @@ local function get_flat_cave_node_types(minp, maxp)
     end)
 end
 
+-- Transform categorized blocks into 
+local function biome_def_to_content_id(def, nt, original_block)
+    local function get_node(name, alt)
+        return function()
+            if name == nil then
+                return alt
+            else
+                return minetest.get_content_id(name)
+            end
+        end
+    end
+
+    local node_air     = get_node(def.node_air, minetest.get_content_id("air"))
+    local node_floor   = get_node(def.node_floor, original_block)
+    local node_stone   = original_block
+    local node_roof    = get_node(def.node_roof, original_block)
+    local node_unknown = original_block
+    local node_wall    = get_node(def.node_wall, original_block)
+
+    if nt == node_type.unknown then
+        return node_unknown
+    elseif nt == node_type.floor then
+        return node_floor()
+    elseif nt == node_type.wall then
+        return node_wall()
+    elseif nt == node_type.roof then
+        return node_roof()
+    elseif nt == node_type.content then
+        return node_air()
+    elseif nt == node_type.stone then
+        return node_stone
+    else
+        return original_block
+    end
+end
+
+local function biome_distance(def, heat, humidity)
+    return (def.heat_point - heat)^2 + (def.humidity_point - humidity)^2
+end
+
 minetest.register_on_generated(function(minp, maxp, blockseed)
     local vminp =
         { x = minp.x - mapgen_buffer
@@ -440,29 +515,35 @@ minetest.register_on_generated(function(minp, maxp, blockseed)
     -- Get threshold values
     local node_types = get_flat_cave_node_types(vminp, vmaxp)
     
-    local node_air   = minetest.get_content_id("air")
-    local node_floor = minetest.get_content_id("mcl_core:glass_green")
-    local node_wall  = minetest.get_content_id("mcl_core:glass_purple")
-    local node_roof  = minetest.get_content_id("mcl_core:glass_red")
-    local node_other = minetest.get_content_id("mcl_core:glass")
+    local heat_points = get_flat_from_noise_params(minp, maxp, heat_noise_params)
+    local humidity_points = get_flat_from_noise_params(minp, maxp, humidity_noise_params)
 
+    -- Map block values
     local nids = Flat3dArray:from_func(vminp, vmaxp, function(i, pos)
         local nt = node_types:get_pos(pos)
 
         if not is_valid_pos(pos, minp, maxp) then
             return flat_data:get_pos(pos)
-        elseif nt == node_type.unknown then
-            return node_other
-        elseif nt == node_type.floor then
-            return node_floor
-        elseif nt == node_type.wall then
-            return node_wall
-        elseif nt == node_type.roof then
-            return node_roof
-        elseif nt == node_type.content then
-            return node_air
-        elseif nt == node_type.stone then
-            return flat_data:get_pos(pos)
+        else
+            local biome = default_biome
+
+            local heat = heat_points:get_pos(pos)
+            local humidity = humidity_points:get_pos(pos)
+
+            for _, def in pairs(noordstar_caves.registered_biomes) do
+                if pos.x < def.minp.x then
+                elseif pos.y < def.minp.y then
+                elseif pos.z < def.minp.z then
+                elseif pos.x > def.maxp.x then
+                elseif pos.y > def.maxp.y then
+                elseif pos.z > def.maxp.z then
+                elseif biome_distance(def, heat, humidity) > biome_distance(biome, heat, humidity) then
+                else
+                    biome = def
+                end
+            end
+
+            return biome_def_to_content_id(biome, nt, flat_data:get_pos(pos))
         end
     end)
 

lua/shape.lua

@@ -47,6 +47,10 @@ function noordstar_caves.register_shape(def)
     end
 end
 
+function noordstar_caves.unregister_shape(name)
+    noordstar_caves.registered_shapes[name] = nil
+end
+
 function noordstar_caves.clear_registered_shapes()
     noordstar_caves.registered_shapes = {}
 end