Make all trees spawn again (#57)

* Make all trees spawn again

* Fix removed value

biome_defs.lua

@@ -1,30 +1,45 @@
 
+-- TODO
+-- Use biomes in the decoration definition depending on their heat_point humidity_point
+-- instead of spawning it with a rather low fill_ratio everywhere
+local ratio_abundant =  0.001
+local ratio_common =    0.0005
+local ratio_normal =    0.0003
+local ratio_uncommon =  0.0002
+local ratio_rare =      0.0001
+local ratio_very_rare = 0.00003
+
+local coniferous_place_on = {
+	xcompat.materials.dirt_with_grass,
+	"default:dirt_with_coniferous_litter"
+}
+
 moretrees.beech_biome = {
 	place_on = xcompat.materials.dirt_with_grass,
+	fill_ratio = ratio_normal,
 }
 
 moretrees.palm_biome = {
 	place_on = xcompat.materials.sand,
 	min_elevation = -1,
 	max_elevation = 1,
-	spawn_by = {xcompat.materials.water_source},
+	fill_ratio = ratio_abundant,
-	num_spawn_by = 10,
 }
 
 moretrees.date_palm_biome = {
 	place_on = xcompat.materials.desert_sand,
 	min_elevation = -1,
-	max_elevation = 10,
+	max_elevation = 8,
-	spawn_by = {xcompat.materials.water_source},
+	fill_ratio = ratio_common,
-	num_spawn_by = 100,
 }
 
 moretrees.date_palm_biome_2 = {
 	place_on = xcompat.materials.desert_sand,
-	min_elevation = 11,
+	min_elevation = 9,
 	max_elevation = 30,
 	spawn_by = {xcompat.materials.water_source},
 	num_spawn_by = 1,
+	fill_ratio = ratio_abundant,
 }
 
 moretrees.apple_tree_biome = {
@@ -32,44 +47,42 @@ moretrees.apple_tree_biome = {
 	min_elevation = 1,
 	max_elevation = 10,
 	biomes = {"deciduous_forest"},
-	fill_ratio = 0.0001,
+	fill_ratio = ratio_rare,
 }
 
 moretrees.oak_biome = {
 	place_on = xcompat.materials.dirt_with_grass,
 	min_elevation = 0,
 	max_elevation = 10,
-	fill_ratio = 0.0003
+	fill_ratio = ratio_normal,
 }
 
 moretrees.sequoia_biome = {
 	place_on = xcompat.materials.dirt_with_grass,
 	min_elevation = 0,
 	max_elevation = 10,
-	fill_ratio = 0.0001,
+	fill_ratio = ratio_rare,
 }
 
 moretrees.birch_biome = {
 	place_on = xcompat.materials.dirt_with_grass,
 	min_elevation = 10,
 	max_elevation = 15,
-	fill_ratio = 0.001,
+	fill_ratio = ratio_common,
 }
 
 moretrees.willow_biome = {
 	place_on = xcompat.materials.dirt_with_grass,
 	min_elevation = -5,
 	max_elevation = 5,
-	spawn_by = {xcompat.materials.water_source},
+	fill_ratio = ratio_uncommon,
-	num_spawn_by = 5,
 }
 
 moretrees.rubber_tree_biome = {
 	place_on = xcompat.materials.dirt_with_grass,
 	min_elevation = -5,
-	max_elevation = 5,
+	max_elevation = 8,
-	spawn_by = {xcompat.materials.water_source},
+	fill_ratio = ratio_normal,
-	num_spawn_by = 10,
 }
 
 moretrees.jungletree_biome = {
@@ -88,15 +101,15 @@ moretrees.jungletree_biome = {
 }
 
 moretrees.spruce_biome = {
-	place_on = xcompat.materials.dirt_with_grass,
+	place_on = coniferous_place_on,
 	min_elevation = 20,
+	fill_ratio = ratio_uncommon,
 }
 
 moretrees.cedar_biome = {
-	place_on = xcompat.materials.dirt_with_grass,
+	place_on = coniferous_place_on,
 	min_elevation = 0,  --Added to solve an issue where cedar trees would sometimes spawn deep underground
-	spawn_by = {xcompat.materials.water_source},
+	fill_ratio = ratio_rare,
-	num_spawn_by = 5,
 }
 
 
@@ -106,7 +119,8 @@ moretrees.poplar_biome = {
 	min_elevation = 0,
 	max_elevation = 50,
 	spawn_by = {xcompat.materials.water_source},
-	num_spawn_by = 1,
+	num_spawn_by = 3,
+	fill_ratio = ratio_abundant,
 }
 
 -- Spawn an occasional poplar elsewhere.
@@ -114,17 +128,17 @@ moretrees.poplar_biome_2 = {
 	place_on = xcompat.materials.dirt_with_grass,
 	min_elevation = 0,
 	max_elevation = 50,
-	spawn_by = {xcompat.materials.water_source},
+	fill_ratio = ratio_very_rare,
-	num_spawn_by = 10,
 }
 
 -- Subterranean lakes provide enough water for poplars to grow
 moretrees.poplar_biome_3 = {
 	place_on = xcompat.materials.dirt_with_grass,
-	min_elevation = 0,
+	min_elevation = -50,
-	max_elevation = 50,
+	max_elevation = 0,
 	spawn_by = {xcompat.materials.water_source},
-	num_spawn_by = 1,
+	num_spawn_by = 3,
+	fill_ratio = ratio_abundant,
 }
 
 moretrees.poplar_small_biome = {
@@ -133,6 +147,7 @@ moretrees.poplar_small_biome = {
 	max_elevation = 50,
 	spawn_by = {xcompat.materials.water_source},
 	num_spawn_by = 1,
+	fill_ratio = ratio_normal,
 }
 
 moretrees.poplar_small_biome_2 = {
@@ -141,15 +156,18 @@ moretrees.poplar_small_biome_2 = {
 	max_elevation = 50,
 	spawn_by = {xcompat.materials.water_source},
 	num_spawn_by = 5,
+	fill_ratio = ratio_abundant,
 }
 
 
 moretrees.fir_biome = {
-	place_on = xcompat.materials.dirt_with_grass,
+	place_on = coniferous_place_on,
 	min_elevation = 25,
+	fill_ratio = ratio_normal,
 }
 
 moretrees.fir_biome_snow = {
 	place_on = {"snow:dirt_with_snow", "snow:snow"},
 	below_nodes = {xcompat.materials.dirt, xcompat.materials.dirt_with_grass, "snow:dirt_with_snow"},
+	fill_ratio = ratio_normal,
 }