Add a priority system for biome structures.

This solves a big part of the degradability problem and allows removing non_degradable_oak_leaves.

assets/cubyz/biomes/rainbow_forest.zig.zon

@@ -21,7 +21,7 @@
 	.structures = .{
 		.{
 			.id = "cubyz:simple_tree",
-			.leaves = "cubyz:non_degradable_oak_leaves",
+			.leaves = "cubyz:oak_leaves",
 			.log = "cubyz:oak_log",
 			.top = "cubyz:oak_top",
 			.chance = 0.48,
@@ -40,6 +40,7 @@
 			.height_variation = 0,
 			.leafRadius = 16,
 			.leafRadius_variation = 3,
+			.priority = 0.1,
 		},
 		.{
 			.id = "cubyz:simple_tree",
@@ -52,6 +53,7 @@
 			.height_variation = 0,
 			.leafRadius = 16,
 			.leafRadius_variation = 3,
+			.priority = 0.1,
 		},
 		.{
 			.id = "cubyz:simple_tree",
@@ -64,6 +66,7 @@
 			.height_variation = 0,
 			.leafRadius = 16,
 			.leafRadius_variation = 3,
+			.priority = 0.1,
 		},
 		.{
 			.id = "cubyz:simple_tree",
@@ -76,6 +79,7 @@
 			.height_variation = 0,
 			.leafRadius = 16,
 			.leafRadius_variation = 3,
+			.priority = 0.1,
 		},
 		.{
 			.id = "cubyz:simple_tree",
@@ -88,6 +92,7 @@
 			.height_variation = 0,
 			.leafRadius = 16,
 			.leafRadius_variation = 3,
+			.priority = 0.1,
 		},
 		.{
 			.id = "cubyz:simple_tree",
@@ -100,6 +105,7 @@
 			.height_variation = 0,
 			.leafRadius = 16,
 			.leafRadius_variation = 3,
+			.priority = 0.1,
 		},
 	},
 }

assets/cubyz/blocks/non_degradable_oak_leaves.zig.zon

@@ -1,14 +0,0 @@
-.{
-	.class = .leaf,
-	.hasItem = false,
-	.hardness = 0.4,
-	.drops = .{
-		"cubyz:oak_leaves",
-		"0.1 cubyz:apple",
-	},
-	.degradable = false,
-	.alwaysViewThrough = true,
-	.absorbedLight = 0x121012,
-	.model = "cubyz:cube",
-	.texture = "cubyz:oak_leaves",
-}

src/server/terrain/StructureMap.zig

@@ -16,10 +16,15 @@ const TerrainGenerationProfile = terrain.TerrainGenerationProfile;
 pub const Structure = struct {
 	generateFn: *const fn(self: *const anyopaque, chunk: *ServerChunk, caveMap: terrain.CaveMap.CaveMapView) void,
 	data: *const anyopaque,
+	priority: f32,
 
 	pub fn generate(self: Structure, chunk: *ServerChunk, caveMap: terrain.CaveMap.CaveMapView) void {
 		self.generateFn(self.data, chunk, caveMap);
 	}
+
+	fn lessThan(_: void, lhs: Structure, rhs: Structure) bool {
+		return lhs.priority < rhs.priority;
+	}
 };
 
 pub const StructureMapFragment = struct {
@@ -54,6 +59,12 @@ pub const StructureMapFragment = struct {
 		main.globalAllocator.destroy(self);
 	}
 
+	fn finishGeneration(self: *StructureMapFragment) void {
+		for(&self.data) |list| {
+			std.sort.insertion(Structure, list.items, {}, Structure.lessThan);
+		}
+	}
+
 	fn getIndex(self: *const StructureMapFragment, x: i32, y: i32, z: i32) usize {
 		std.debug.assert(x >= 0 and x < size*self.pos.voxelSize and y >= 0 and y < size*self.pos.voxelSize and z >= 0 and z < size*self.pos.voxelSize); // Coordinates out of range.
 		return @intCast(((x >> main.chunk.chunkShift+self.voxelShift)*chunkedSize + (y >> main.chunk.chunkShift+self.voxelShift))*chunkedSize + (z >> main.chunk.chunkShift+self.voxelShift));
@@ -151,6 +162,7 @@ fn cacheInit(pos: ChunkPosition) *StructureMapFragment {
 	for(profile.structureMapGenerators) |generator| {
 		generator.generate(mapFragment, profile.seed ^ generator.generatorSeed);
 	}
+	mapFragment.finishGeneration();
 	_ = @atomicRmw(u16, &mapFragment.refCount.raw, .Add, 1, .monotonic);
 	return mapFragment;
 }

src/server/terrain/biomes.zig

@@ -28,6 +28,7 @@ pub const SimpleStructureModel = struct { // MARK: SimpleStructureModel
 	vtable: VTable,
 	data: *anyopaque,
 	chance: f32,
+	priority: f32,
 	generationMode: GenerationMode,
 
 	pub fn initModel(parameters: ZonElement) ?SimpleStructureModel {
@@ -40,6 +41,7 @@ pub const SimpleStructureModel = struct { // MARK: SimpleStructureModel
 			.vtable = vtable,
 			.data = vtable.loadModel(arena.allocator(), parameters),
 			.chance = parameters.get(f32, "chance", 0.1),
+			.priority = parameters.get(f32, "priority", 1),
 			.generationMode = std.meta.stringToEnum(GenerationMode, parameters.get([]const u8, "generationMode", "")) orelse vtable.generationMode,
 		};
 	}

src/server/terrain/structuremapgen/SimpleStructureGen.zig

@@ -64,6 +64,7 @@ pub fn generate(map: *StructureMapFragment, worldSeed: u64) void {
 						map.addStructure(.{
 							.data = @ptrCast(data),
 							.generateFn = &SimpleStructure.generate,
+							.priority = model.priority,
 						}, .{px -% margin, py -% margin, relZ -% margin -% 15}, .{px +% margin, py +% margin, relZ +% margin +% 15});
 						break;
 					} else {
@@ -102,6 +103,7 @@ pub fn generate(map: *StructureMapFragment, worldSeed: u64) void {
 						map.addStructure(.{
 							.data = @ptrCast(data),
 							.generateFn = &SimpleStructure.generate,
+							.priority = model.priority,
 						}, .{px -% margin, py -% margin, relZ -% margin -% 15}, .{px +% margin, py +% margin, relZ +% margin +% 15});
 						break;
 					} else {