add LuaGeneratorScript::loadStructures

res/generators/default.lua

@@ -55,6 +55,12 @@ biomes = {
     }
 }
 
+function load_structures()
+    local structures = {}
+    table.insert(structures, generation.load_structure("core:default.files/tree0"))
+    return structures
+end
+
 local function _generate_heightmap(x, y, w, h, seed, s)
     local umap = Heightmap(w, h)
     local vmap = Heightmap(w, h)

res/scripts/world.lua

@@ -1,4 +1,3 @@
 -- use for engine development tests
 -- must be empty in release
 -- must not be modified by content-packs
-print(generation.load_structure("core:default.files/tree0"))

src/logic/scripting/scripting_world_generation.cpp

@@ -30,6 +30,26 @@ public:
       seaLevel(seaLevel) 
       {}
 
+    std::vector<std::shared_ptr<VoxelStructure>> loadStructures() override {
+        std::vector<std::shared_ptr<VoxelStructure>> structures;
+
+        auto L = lua::get_main_thread();
+        lua::pushenv(L, *env);
+        if (lua::getfield(L, "load_structures")) {
+            if (lua::call_nothrow(L, 0, 1)) {
+                for (int i = 1; i <= lua::objlen(L, -1); i++) {
+                    lua::rawgeti(L, i);
+                    if (auto lstruct =
+                            lua::touserdata<lua::LuaVoxelStructure>(L, -1)) {
+                        structures.push_back(lstruct->getStructure());
+                    }
+                }
+            }
+        }
+        lua::pop(L);
+        return structures;
+    }
+
     std::shared_ptr<Heightmap> generateHeightmap(
         const glm::ivec2& offset, const glm::ivec2& size, uint64_t seed
     ) override {

src/world/generator/GeneratorDef.hpp

@@ -101,7 +101,7 @@ public:
     virtual ~GeneratorScript() = default;
 
     /// @brief Load all structures
-    //virtual std::vector<std::shared_ptr<VoxelStructure>> loadStructures() = 0;
+    virtual std::vector<std::shared_ptr<VoxelStructure>> loadStructures() = 0;
 
     /// @brief Generates a heightmap with values in range 0..1
     /// @param offset position of the heightmap in the world

src/world/generator/WorldGenerator.cpp

@@ -46,6 +46,8 @@ WorldGenerator::WorldGenerator(
         }
         generateHeightmap(found->second.get(), x, z);
     });
+
+    structures = def.script->loadStructures();
 }
 
 WorldGenerator::~WorldGenerator() {}

src/world/generator/WorldGenerator.hpp

@@ -62,7 +62,7 @@ class WorldGenerator {
     /// @brief Chunk prototypes loading surround map
     SurroundMap surroundMap;
 
-    std::vector<std::unique_ptr<VoxelStructure>> structures;
+    std::vector<std::shared_ptr<VoxelStructure>> structures;
 
     /// @brief Generate chunk prototype (see ChunkPrototype)
     /// @param x chunk position X divided by CHUNK_W