commit f410d037e772c53f72aaa57599d516c659cd2bd6
Author: Sara <sara@objectionable.solutions>
Date:   Mon Apr 13 12:30:06 2026 +0200

    feat: extracted code from project

diff --git a/SCsub b/SCsub
new file mode 100644
index 0000000..2760ab7
--- /dev/null
+++ b/SCsub
@@ -0,0 +1,3 @@
+Import('env')
+
+env.add_source_files(env.modules_sources, "*.cpp")
diff --git a/TODO.org b/TODO.org
new file mode 100644
index 0000000..c7a7ff5
--- /dev/null
+++ b/TODO.org
@@ -0,0 +1,14 @@
+- [x] Cache chunk meshes
+- [ ] Noise modifier
+- [ ] Min/Max modifier
+- [ ] Only load defined chunks
+- [ ] More accurate modifier bounds
+- [ ] Separate terrain module into it's own repository
+- [ ] Texturing step
+- [ ] Use Semaphores in mesh gen multi-threading
+- [ ] Separate source files for terrain modifiers
+- [x] Stop threads when generation finishes
+- [ ] Regenerate chunks when deleting/reordering modifiers
+- [x] Stop processing terrain after generation is complete
+- [x] Don't start generation threads if all meshes are cached
+- [ ] Scaling modifiers
diff --git a/config.py b/config.py
new file mode 100644
index 0000000..58c88bf
--- /dev/null
+++ b/config.py
@@ -0,0 +1,5 @@
+def can_build(env, platform):
+    return True;
+
+def configure(env):
+    pass;
diff --git a/register_types.cpp b/register_types.cpp
new file mode 100644
index 0000000..150ee0c
--- /dev/null
+++ b/register_types.cpp
@@ -0,0 +1,25 @@
+#include "register_types.h"
+
+#include "core/object/class_db.h"
+#include "terrain/terrain.h"
+#include "terrain/terrain_chunk.h"
+#include "terrain/terrain_modifier.h"
+
+void initialize_terrain_module(ModuleInitializationLevel p_level) {
+	if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
+		return;
+	}
+	ClassDB::register_class<Terrain>();
+	ClassDB::register_abstract_class<TerrainModifier>();
+	ClassDB::register_class<TerrainModifierDistance>();
+	ClassDB::register_class<TerrainModifierPath>();
+	ClassDB::register_class<TerrainModifierPathPoint>();
+	ClassDB::register_class<TerrainModifierComposite>();
+	ClassDB::register_class<TerrainChunkMesh>();
+}
+
+void uninitialize_terrain_module(ModuleInitializationLevel p_level) {
+	if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
+		return;
+	}
+}
diff --git a/register_types.h b/register_types.h
new file mode 100644
index 0000000..8500356
--- /dev/null
+++ b/register_types.h
@@ -0,0 +1,9 @@
+#ifndef TERRAIN_REGISTER_TYPES_H
+#define TERRAIN_REGISTER_TYPES_H
+
+#include "modules/register_module_types.h"
+
+void initialize_terrain_module(ModuleInitializationLevel p_level);
+void uninitialize_terrain_module(ModuleInitializationLevel p_level);
+
+#endif // !TERRAIN_REGISTER_TYPES_H
diff --git a/terrain.cpp b/terrain.cpp
new file mode 100644
index 0000000..bcbee7f
--- /dev/null
+++ b/terrain.cpp
@@ -0,0 +1,329 @@
+#include "terrain.h"
+#include "terrain/terrain_chunk.h"
+#include "terrain/terrain_modifier.h"
+
+void Terrain::_bind_methods() {
+	BIND_HPROPERTY(Variant::OBJECT, mesh_material, PROPERTY_HINT_RESOURCE_TYPE, "Material");
+	BIND_PROPERTY(Variant::INT, side_length);
+	BIND_PROPERTY(Variant::INT, chunk_size);
+	BIND_PROPERTY(Variant::INT, thread_count);
+	BIND_HPROPERTY(Variant::ARRAY, terrain_meshes, PROPERTY_HINT_ARRAY_TYPE, vformat("%s/%s:TerrainMeshChunk", Variant::OBJECT, PROPERTY_HINT_NODE_TYPE), PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_READ_ONLY);
+}
+
+void Terrain::child_order_changed() {
+	this->modifiers.clear();
+	for (Variant var : get_children()) {
+		if (TerrainModifier * mod{ cast_to<TerrainModifier>(var) }) {
+			mod->set_terrain(this);
+			this->modifiers.push_back(mod);
+		}
+	}
+}
+
+void Terrain::update_meshes() {
+	size_t num{ 1 };
+	this->dirty_meshes_lock.lock();
+	num = num > this->dirty_meshes.size() ? this->dirty_meshes.size() : num;
+	this->dirty_meshes_lock.unlock();
+	for (size_t i{ 0 }; i < num; i++) {
+		this->dirty_meshes_lock.lock();
+		TerrainChunkMesh *mesh{ this->dirty_meshes[0] };
+		this->dirty_meshes.remove_at(0);
+		this->dirty_meshes_lock.unlock();
+		mesh->apply_new_mesh();
+	}
+}
+
+void Terrain::update_threads() {
+	this->workload_lock.lock();
+	if (this->workload.is_empty()) {
+		this->threads_stop = true;
+		this->workload_lock.unlock();
+		for (Thread &thread : this->threads) {
+			if (thread.is_started()) {
+				thread.wait_to_finish();
+			}
+		}
+	} else {
+		print_line(vformat("Starting threads; workload: %d", this->workload.size()));
+		this->threads_stop = false;
+		for (Thread &thread : this->threads) {
+			if (!thread.is_started()) {
+				thread.start(Terrain::generate_meshes_thread, this);
+			}
+		}
+		this->workload_lock.unlock();
+	}
+}
+
+void Terrain::update_process() {
+	for (Thread &thread : this->threads) {
+		if (thread.is_started()) {
+			return;
+		}
+	}
+	this->dirty_meshes_lock.lock();
+	bool workload_empty{ this->dirty_meshes.is_empty() };
+	this->dirty_meshes_lock.unlock();
+	if (!workload_empty) {
+		return;
+	}
+	this->workload_lock.lock();
+	workload_empty = this->workload.is_empty();
+	this->workload_lock.unlock();
+	if (!workload_empty) {
+		return;
+	}
+	print_line("Terrain processing stopped");
+	set_process(false);
+}
+
+void Terrain::synchronous_generate_terrain() {
+	print_line("Force-regenerating entire terrain in one go.");
+	this->workload_lock.lock();
+	this->threads_stop = false;
+	this->workload.clear();
+	this->workload.append_array(this->meshes);
+	for (Thread &thread : this->threads) {
+		if (!thread.is_started()) {
+			thread.start(&Terrain::generate_meshes_thread, this);
+		}
+	}
+	do {
+		this->workload_lock.unlock();
+		Thread::yield();
+		this->workload_lock.lock();
+	} while (!this->workload.is_empty());
+	this->threads_stop = true;
+	this->workload_lock.unlock();
+	for (Thread &thread : this->threads) {
+		thread.wait_to_finish();
+	}
+	for (TerrainChunkMesh *mesh : this->dirty_meshes) {
+		mesh->apply_new_mesh();
+	}
+	this->dirty_meshes.clear();
+}
+
+void Terrain::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_CHILD_ORDER_CHANGED:
+			if (is_ready()) {
+				this->child_order_changed();
+			}
+			return;
+		case NOTIFICATION_READY: {
+			this->meshes.clear();
+			this->modifiers.clear();
+			for (Variant var : get_children()) {
+				if (TerrainChunkMesh * mesh{ cast_to<TerrainChunkMesh>(var) }) {
+					this->meshes.push_back(mesh);
+					mesh->set_terrain(this);
+				}
+				if (TerrainModifier * mod{ cast_to<TerrainModifier>(var) }) {
+					this->modifiers.push_back(mod);
+					mod->set_terrain(this);
+				}
+			}
+			size_t expected_size{ this->side_length / this->chunk_size };
+			if (this->meshes.size() != expected_size * expected_size) {
+				construct_chunk_grid();
+				synchronous_generate_terrain();
+			}
+			return;
+		}
+		case NOTIFICATION_PROCESS:
+			update_meshes();
+			update_threads();
+			update_process();
+			return;
+		case NOTIFICATION_EXIT_TREE:
+			this->workload_lock.lock();
+			this->threads_stop = true;
+			this->workload_lock.unlock();
+			for (Thread &thread : this->threads) {
+				if (thread.is_started()) {
+					thread.wait_to_finish();
+				}
+			}
+			return;
+	}
+}
+
+void Terrain::generate_meshes_thread(void *terrain) {
+	Terrain *self{ static_cast<Terrain *>(terrain) };
+	print_line("thread", Thread::get_caller_id(), "start");
+	for (;;) {
+		self->workload_lock.lock();
+		if (self->threads_stop) {
+			self->workload_lock.unlock();
+			print_line(Thread::get_caller_id(), "exiting");
+			break;
+		}
+		if (self->workload.is_empty()) {
+			self->workload_lock.unlock();
+			Thread::yield();
+			continue;
+		}
+		TerrainChunkMesh *mesh{ self->workload[0] };
+		self->workload.remove_at(0);
+		self->workload_lock.unlock();
+		if (!mesh->is_inside_tree()) {
+			print_line(Thread::get_caller_id(), "mesh is outside tree, exiting");
+			break;
+		}
+		mesh->update_mesh();
+		Thread::yield();
+	}
+	print_line(Thread::get_caller_id(), "done");
+	return;
+}
+
+void Terrain::construct_chunk_grid() {
+	print_line("Constructing chunk grid");
+	this->workload_lock.lock();
+	this->threads_stop = true;
+	this->workload_lock.unlock();
+	for (Thread &thread : this->threads) {
+		if (thread.is_started()) {
+			thread.wait_to_finish();
+		}
+	}
+	this->workload_lock.lock();
+	for (TerrainChunkMesh *mesh : this->meshes) {
+		remove_child(mesh);
+		mesh->queue_free();
+	}
+	this->meshes.clear();
+	this->workload.clear();
+	size_t const chunks_per_side{ this->side_length / this->chunk_size };
+	Vector3 const origin{ (float)this->chunk_size / 2.f, 0.f, (float)this->chunk_size / 2.f };
+	for (size_t y{ 0 }; y < chunks_per_side; ++y) {
+		for (size_t x{ 0 }; x < chunks_per_side; ++x) {
+			TerrainChunkMesh *chunk{ memnew(TerrainChunkMesh) };
+			chunk->set_size(this->chunk_size);
+			chunk->set_detail(this->detail);
+			chunk->set_terrain(this);
+			chunk->set_material_override(this->mesh_material);
+			chunk->set_position(origin + Vector3{ (float)this->chunk_size * (float)x, 0.f, (float)this->chunk_size * (float)y });
+			chunk->set_name(vformat("Chunk%dx%d", x, y));
+			add_child(chunk);
+			chunk->set_owner(get_owner());
+			this->meshes.push_back(chunk);
+			this->workload.push_back(chunk);
+		}
+	}
+	this->threads_stop = false;
+	this->dirty_meshes.clear();
+	this->workload_lock.unlock();
+	set_process(true);
+}
+
+float Terrain::height_at(Vector2 world_coordinate) {
+	float height{ 0 };
+	for (TerrainModifier *mod : this->modifiers) {
+		if (!mod->is_inside_tree()) {
+			return height;
+		}
+		height = mod->evaluate_at(world_coordinate, height);
+	}
+	return height;
+}
+
+void Terrain::push_changed(Rect2 area) {
+	for (TerrainChunkMesh *mesh : this->meshes) {
+		this->workload_lock.lock();
+		if (area.intersects(mesh->get_bounds()) && !this->workload.has(mesh)) {
+			workload.push_back(mesh);
+		}
+		this->workload_lock.unlock();
+	}
+	set_process(true);
+}
+
+void Terrain::mesh_dirty(TerrainChunkMesh *mesh) {
+	this->dirty_meshes_lock.lock();
+	this->dirty_meshes.push_back(mesh);
+	callable_mp(cast_to<Node>(this), &self_type::set_process).call_deferred(true);
+	this->dirty_meshes_lock.unlock();
+}
+
+void Terrain::set_mesh_material(Ref<Material> material) {
+	this->mesh_material = material;
+	for (TerrainChunkMesh *mesh : this->meshes) {
+		mesh->set_material_override(material);
+	}
+}
+
+Ref<Material> Terrain::get_mesh_material() const {
+	return this->mesh_material;
+}
+
+void Terrain::set_side_length(size_t length) {
+	this->side_length = length;
+	if (is_inside_tree()) {
+		construct_chunk_grid();
+	}
+}
+
+size_t Terrain::get_side_length() const {
+	return this->side_length;
+}
+
+void Terrain::set_chunk_size(size_t size) {
+	this->chunk_size = size;
+	if (is_inside_tree()) {
+		construct_chunk_grid();
+	}
+}
+
+size_t Terrain::get_chunk_size() const {
+	return this->chunk_size;
+}
+
+void Terrain::set_detail(size_t detail) {
+	this->detail = detail;
+	if (is_inside_tree()) {
+		construct_chunk_grid();
+	}
+}
+
+size_t Terrain::get_detail() const {
+	return this->detail;
+}
+
+void Terrain::set_thread_count(size_t num) {
+	this->workload_lock.lock();
+	this->threads_stop = true;
+	this->workload_lock.unlock();
+	for (Thread &thread : this->threads) {
+		thread.wait_to_finish();
+	}
+	this->threads_stop = false;
+	this->threads.resize_initialized(num);
+}
+
+size_t Terrain::get_thread_count() const {
+	return this->threads.size();
+}
+
+void Terrain::set_terrain_meshes(Array array) {
+	return;
+	this->meshes.clear();
+	for (Variant var : array) {
+		if (TerrainChunkMesh * mesh{ cast_to<TerrainChunkMesh>(var) }) {
+			mesh->set_terrain(this);
+			this->meshes.push_back(mesh);
+		}
+	}
+}
+
+Array Terrain::get_terrain_meshes() const {
+	Array a{};
+	for (TerrainChunkMesh *mesh : this->meshes) {
+		a.push_back(mesh);
+	}
+	return a;
+}
diff --git a/terrain.h b/terrain.h
new file mode 100644
index 0000000..b8dae5e
--- /dev/null
+++ b/terrain.h
@@ -0,0 +1,61 @@
+#pragma once
+
+#include "core/math/rect2.h"
+#include "core/os/mutex.h"
+#include "core/os/thread.h"
+#include "core/templates/vector.h"
+#include "scene/main/node.h"
+#include "scene/resources/material.h"
+class TerrainChunkMesh;
+class TerrainModifier;
+
+class Terrain : public Node {
+	GDCLASS(Terrain, Node);
+	static void _bind_methods();
+	void child_order_changed();
+	void update_meshes();
+	void update_threads();
+	void update_process();
+	void synchronous_generate_terrain();
+
+protected:
+	void _notification(int what);
+	static void generate_meshes_thread(void *terrain);
+
+public:
+	void construct_chunk_grid();
+	float height_at(Vector2 world_coordinate);
+	void push_changed(Rect2 area);
+	void mesh_dirty(TerrainChunkMesh *mesh);
+
+private:
+	Ref<Material> mesh_material{};
+	Vector<TerrainChunkMesh *> workload{};
+	bool threads_stop{ false };
+	Mutex workload_lock;
+
+	Vector<TerrainChunkMesh *> dirty_meshes{};
+	Mutex dirty_meshes_lock{};
+
+	Vector<TerrainChunkMesh *> meshes{};
+	Vector<TerrainModifier *> modifiers{};
+	LocalVector<Thread> threads{};
+
+	size_t side_length{ 200 };
+	size_t chunk_size{ 50 };
+	size_t detail{ 1 };
+
+public:
+	void set_mesh_material(Ref<Material> material);
+	Ref<Material> get_mesh_material() const;
+	void set_side_length(size_t length);
+	size_t get_side_length() const;
+	void set_chunk_size(size_t size);
+	size_t get_chunk_size() const;
+	void set_detail(size_t detail);
+	size_t get_detail() const;
+	void set_thread_count(size_t num);
+	size_t get_thread_count() const;
+	void set_terrain_meshes(Array array);
+	Array get_terrain_meshes() const;
+};
diff --git a/terrain_chunk.cpp b/terrain_chunk.cpp
new file mode 100644
index 0000000..ac81ac3
--- /dev/null
+++ b/terrain_chunk.cpp
@@ -0,0 +1,137 @@
+#include "terrain_chunk.h"
+#include "core/math/math_defs.h"
+#include "core/math/math_funcs.h"
+#include "core/object/object.h"
+#include "core/variant/variant.h"
+#include "scene/3d/physics/collision_shape_3d.h"
+#include "scene/3d/physics/static_body_3d.h"
+#include "scene/resources/3d/height_map_shape_3d.h"
+#include "scene/resources/surface_tool.h"
+#include "terrain/terrain.h"
+
+void TerrainChunkMesh::_bind_methods() {
+	BIND_HPROPERTY(Variant::OBJECT, shape, PROPERTY_HINT_RESOURCE_TYPE, "HeightMapShape3D", PROPERTY_USAGE_READ_ONLY | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_STORAGE);
+	BIND_HPROPERTY(Variant::INT, size, PROPERTY_HINT_NONE, "", PROPERTY_USAGE_READ_ONLY | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_STORAGE);
+}
+
+void TerrainChunkMesh::ready() {
+	this->position_buffer = get_global_position();
+	float const sizef{ (float)get_size() };
+	this->bounds.position = { this->position_buffer.x - sizef / 2.f, this->position_buffer.z - sizef / 2.f };
+	this->bounds.size = { sizef, sizef };
+
+	add_child(this->body = memnew(StaticBody3D));
+	ERR_FAIL_COND_EDMSG(this->body == nullptr, "Failed to instantiate StaticBody3D");
+	this->body->add_child(this->collider = memnew(CollisionShape3D));
+	this->body->set_owner(this);
+	ERR_FAIL_COND_EDMSG(this->collider == nullptr, "Failed to instantiate CollisionShape3D");
+	this->collider->set_owner(this);
+	if (this->shape.is_null()) {
+		this->shape = memnew(HeightMapShape3D);
+		this->shape->set_map_depth(heightmap_side_length());
+		this->shape->set_map_width(heightmap_side_length());
+	} else {
+		this->heightmap.append_array(this->shape->get_map_data());
+	}
+	ERR_FAIL_COND_EDMSG(!this->shape.is_valid(), "Failed to instantiate HeightMapShape3D");
+	this->collider->set_shape(this->shape);
+}
+
+void TerrainChunkMesh::generate_vertices() {
+	ERR_FAIL_COND_EDMSG(this->terrain == nullptr, "TerrainChunkMesh::generate_vertices: no terrain assigned");
+	ERR_FAIL_COND_EDMSG(this->size <= 0.f, "TerrainChunkMesh::generate_vertices: size <= 0");
+	ERR_FAIL_COND_EDMSG(points_per_side() <= 0, "TerrainChunkMesh::generate_vertices: points per side <= 0");
+	float const half_extent{ (float)this->size / 2.f };
+	float const point_distance{ (float)this->size / ((float)points_per_side() - 1) };
+	Vector3 origin{ this->position_buffer - Vector3{ half_extent, 0, half_extent } };
+	for (size_t x{ 0 }; x < points_per_side(); ++x) {
+		for (size_t y{ 0 }; y < points_per_side(); ++y) {
+			Vector2 const coordinate{ origin.x + point_distance * x, origin.z + point_distance * y };
+			this->surface->set_uv({ (float)x / (float)points_per_side(), (float)y / (float)points_per_side() });
+			float height{ this->terrain->height_at(coordinate) };
+			this->surface->add_vertex({ coordinate.x - this->position_buffer.x, height, coordinate.y - this->position_buffer.z });
+		}
+	}
+	this->heightmap.resize_initialized(heightmap_side_length() * heightmap_side_length());
+	for (size_t x{ 0 }; x < heightmap_side_length(); x++) {
+		for (size_t y{ 0 }; y < heightmap_side_length(); y++) {
+			Vector2 coordinate{ origin.x + x, origin.z + y };
+			this->heightmap.set(x + y * heightmap_side_length(), this->terrain->height_at(coordinate));
+		}
+	}
+}
+
+void TerrainChunkMesh::generate_faces() {
+	LocalVector<SurfaceTool::Vertex> &verts{ this->surface->get_vertex_array() };
+	ERR_FAIL_COND_EDMSG(verts.size() == 0, "TerrainChunkMesh::generate_faces: no vertices in surface, call generate_vertices first");
+	size_t const faces_per_side{ points_per_side() - 1 };
+	for (size_t x{ 0 }; x < faces_per_side; ++x) {
+		for (size_t y{ 0 }; y < faces_per_side; ++y) {
+			size_t const tl{ x + y * points_per_side() };
+			float tl_br{ verts[tl].vertex.distance_to(verts[tl + points_per_side() + 1].vertex) };
+			float tr_bl{ verts[tl + 1].vertex.distance_to(verts[tl + points_per_side()].vertex) };
+			if (tl_br < tr_bl) {
+				surface->add_index(tl);
+				surface->add_index(tl + points_per_side() + 1);
+				surface->add_index(tl + 1);
+				surface->add_index(tl);
+				surface->add_index(tl + points_per_side());
+				surface->add_index(tl + points_per_side() + 1);
+			} else {
+				surface->add_index(tl + points_per_side());
+				surface->add_index(tl + points_per_side() + 1);
+				surface->add_index(tl + 1);
+				surface->add_index(tl + 1);
+				surface->add_index(tl);
+				surface->add_index(tl + points_per_side());
+			}
+		}
+	}
+}
+
+void TerrainChunkMesh::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_ENTER_TREE:
+			if (!is_ready()) {
+				ready();
+			}
+			return;
+	}
+}
+
+void TerrainChunkMesh::apply_new_mesh() {
+	this->lock.lock();
+	set_mesh(this->new_mesh);
+	if (this->shape->get_map_depth() != heightmap_side_length() || this->shape->get_map_width() != heightmap_side_length()) {
+		this->shape->set_map_depth(heightmap_side_length());
+		this->shape->set_map_width(heightmap_side_length());
+	}
+	this->shape->set_map_data(heightmap);
+	this->lock.unlock();
+}
+
+void TerrainChunkMesh::update_mesh() {
+	ERR_FAIL_COND_EDMSG(this->size <= 0.f, "TerrainChunkMesh::generate: size <= 0");
+	ERR_FAIL_COND_EDMSG(points_per_side() <= 0, "TerrainChunkMesh::generate: points per side <= 0");
+	this->lock.lock();
+	this->surface = memnew(SurfaceTool);
+	this->surface->begin(Mesh::PRIMITIVE_TRIANGLES);
+	generate_vertices();
+	generate_faces();
+	this->surface->generate_normals();
+	this->surface->generate_tangents();
+	this->new_mesh = memnew(ArrayMesh);
+	this->surface->commit(this->new_mesh);
+	this->lock.unlock();
+	this->terrain->mesh_dirty(this);
+}
+
+size_t TerrainChunkMesh::points_per_side() const {
+	return this->size * this->detail;
+}
+
+int TerrainChunkMesh::heightmap_side_length() const {
+	return get_size() + 1;
+}
diff --git a/terrain_chunk.h b/terrain_chunk.h
new file mode 100644
index 0000000..fb427e6
--- /dev/null
+++ b/terrain_chunk.h
@@ -0,0 +1,50 @@
+#pragma once
+
+#include "core/math/rect2.h"
+#include "macros.h"
+#include "scene/3d/mesh_instance_3d.h"
+#include "scene/3d/physics/collision_shape_3d.h"
+#include "scene/3d/physics/static_body_3d.h"
+#include "scene/resources/3d/height_map_shape_3d.h"
+#include "scene/resources/mesh.h"
+#include "scene/resources/surface_tool.h"
+class Terrain;
+
+class TerrainChunkMesh : public MeshInstance3D {
+	GDCLASS(TerrainChunkMesh, MeshInstance3D);
+	static void _bind_methods();
+	void ready();
+	void generate_vertices();
+	void generate_faces();
+
+protected:
+	void _notification(int what);
+
+public:
+	void apply_new_mesh();
+	void update_mesh();
+	size_t points_per_side() const;
+	int heightmap_side_length() const;
+
+private:
+	Mutex lock{};
+	Vector3 position_buffer{};
+	Ref<SurfaceTool> surface{};
+	Ref<ArrayMesh> new_mesh{};
+	Terrain *terrain{ nullptr };
+	size_t detail{ 1 };
+	size_t size{ 1 };
+	Rect2 bounds{};
+
+	Ref<HeightMapShape3D> shape{};
+	StaticBody3D *body{ nullptr };
+	CollisionShape3D *collider{ nullptr };
+	Vector<real_t> heightmap{};
+
+public:
+	GET_SET_FNS(Rect2, bounds);
+	GET_SET_FNS(Terrain *, terrain);
+	GET_SET_FNS(Ref<HeightMapShape3D>, shape);
+	GET_SET_FNS(size_t, detail);
+	GET_SET_FNS(size_t, size);
+};
diff --git a/terrain_modifier.cpp b/terrain_modifier.cpp
new file mode 100644
index 0000000..f8ada28
--- /dev/null
+++ b/terrain_modifier.cpp
@@ -0,0 +1,475 @@
+#include "terrain_modifier.h"
+#include "core/config/engine.h"
+#include "core/math/math_funcs.h"
+#include "core/variant/variant.h"
+#include "macros.h"
+#include "scene/main/node.h"
+#include "terrain/terrain.h"
+#include <algorithm>
+
+String TerrainModifier::sig_terrain_changed{ "terrain_changed" };
+
+void TerrainModifier::_bind_methods() {
+	ADD_SIGNAL(MethodInfo(sig_terrain_changed, PropertyInfo(Variant::OBJECT, "terrain", PROPERTY_HINT_NODE_TYPE, "Terrain")));
+}
+
+void TerrainModifier::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_ENTER_TREE:
+			if (Engine::get_singleton()->is_editor_hint()) {
+				set_notify_transform(true);
+			}
+			this->thread_safe_global_position = get_global_position();
+		case NOTIFICATION_TRANSFORM_CHANGED:
+			this->thread_safe_global_position = get_global_position();
+			return;
+	}
+}
+
+void TerrainModifier::push_changed(Rect2 area) {
+	if (this->terrain) {
+		this->terrain->push_changed(area);
+	}
+}
+
+float TerrainModifier::evaluate_at(Vector2 world_coordinate, float before) {
+	Vector3 const global_position{ get_thread_safe_global_position() };
+	return global_position.y;
+}
+
+void TerrainModifier::set_bounds(Rect2 bounds) {
+	if (this->bounds != bounds) {
+		push_changed(bounds);
+		push_changed(this->bounds);
+		this->bounds = bounds;
+	}
+}
+
+Rect2 TerrainModifier::get_bounds() const {
+	return this->bounds;
+}
+
+Vector3 TerrainModifier::get_thread_safe_global_position() const {
+	return this->thread_safe_global_position;
+}
+
+void SharedMutex::lock_shared() {
+	this->lock.lock();
+	this->shared_count++;
+	this->lock.unlock();
+}
+
+void SharedMutex::unlock_shared() {
+	this->lock.lock();
+	this->shared_count--;
+	this->lock.unlock();
+}
+
+void SharedMutex::lock_exclusive() {
+	while (true) {
+		this->lock.lock();
+		if (this->shared_count == 0) {
+			return;
+		}
+		this->lock.unlock();
+	}
+}
+
+void SharedMutex::unlock_exclusive() {
+	this->lock.unlock();
+}
+
+void TerrainModifierDistance::_bind_methods() {
+	BIND_HPROPERTY(Variant::OBJECT, distance_weight_curve, PROPERTY_HINT_RESOURCE_TYPE, "Curve");
+}
+
+void TerrainModifierDistance::curves_changed() {
+	if (!update_bounds()) {
+		push_changed(get_bounds());
+	}
+	this->lock.lock_exclusive();
+	this->distance_weight_curve_buffer = this->distance_weight_curve.is_valid() ? this->distance_weight_curve->duplicate(true) : nullptr;
+	this->lock.unlock_exclusive();
+}
+
+bool TerrainModifierDistance::update_bounds() {
+	Rect2 const before{ get_bounds() };
+	Rect2 bounds{};
+	Vector3 position{ get_thread_safe_global_position() };
+	bounds.position = { position.x, position.z };
+	bounds.size = { 0, 0 };
+	this->lock.lock_shared();
+	if (this->distance_weight_curve.is_valid()) {
+		float const max_radius{ this->distance_weight_curve->get_max_domain() };
+		float const max_diameter{ 2.f * max_radius };
+		bounds.size = { max_diameter, max_diameter };
+		bounds.position -= { max_radius, max_radius };
+	}
+	bool const changed{ before != bounds };
+	this->lock.unlock_shared();
+	this->lock.lock_exclusive();
+	set_bounds(bounds);
+	this->lock.unlock_exclusive();
+	return changed;
+}
+
+void TerrainModifierDistance::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_READY:
+			update_bounds();
+			set_notify_transform(true);
+			return;
+		case NOTIFICATION_TRANSFORM_CHANGED:
+			if (is_inside_tree()) {
+				if (!update_bounds()) {
+					push_changed(get_bounds());
+				}
+			}
+			return;
+	}
+}
+
+float TerrainModifierDistance::distance_at(Vector2 const &world_coordinate) {
+	Vector3 const global_position{ get_thread_safe_global_position() };
+	return world_coordinate.distance_to({ global_position.x, global_position.z });
+}
+
+float TerrainModifierDistance::evaluate_at(Vector2 world_coordinate, float before) {
+	this->lock.lock_shared();
+	if (this->distance_weight_curve_buffer.is_null()) {
+		this->lock.unlock_shared();
+		return before;
+	}
+	float const distance{ distance_at(world_coordinate) };
+	if (distance >= this->distance_weight_curve_buffer->get_max_domain()) {
+		this->lock.unlock_shared();
+		return before;
+	}
+	float const weight_offset{ std::clamp(distance, this->distance_weight_curve_buffer->get_min_domain(), this->distance_weight_curve_buffer->get_max_domain()) };
+	float const weight{ this->distance_weight_curve_buffer->sample(weight_offset) };
+	float out{ weight <= 0.f ? before : Math::lerp(before, get_thread_safe_global_position().y, weight) };
+	this->lock.unlock_shared();
+
+	return out;
+}
+
+PackedStringArray TerrainModifierDistance::get_configuration_warnings() const {
+	PackedStringArray warnings{ super_type::get_configuration_warnings() };
+	if (this->distance_weight_curve.is_null()) {
+		warnings.push_back("distance_weight_curve is invalid, add a valid distance_weight_curve");
+	}
+	return warnings;
+}
+
+void TerrainModifierDistance::set_distance_weight_curve(Ref<Curve> curve) {
+	this->lock.lock_exclusive();
+	if (Engine::get_singleton()->is_editor_hint()) {
+		if (this->distance_weight_curve.is_valid()) {
+			this->distance_weight_curve->disconnect_changed(callable_mp(this, &self_type::curves_changed));
+		}
+		if (curve.is_valid()) {
+			curve->connect_changed(callable_mp(this, &self_type::curves_changed));
+		}
+	}
+	this->distance_weight_curve = curve;
+	this->lock.unlock_exclusive();
+	curves_changed();
+	update_configuration_warnings();
+}
+
+Ref<Curve> TerrainModifierDistance::get_distance_weight_curve() const {
+	return this->distance_weight_curve;
+}
+
+void TerrainModifierPathPoint::_bind_methods() {}
+
+void TerrainModifierPathPoint::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_ENTER_TREE:
+			this->path = cast_to<TerrainModifierPath>(get_parent());
+			return;
+		case NOTIFICATION_READY:
+			set_notify_transform(true);
+			if (this->path) {
+				this->path->path_changed();
+			}
+			return;
+		case NOTIFICATION_TRANSFORM_CHANGED:
+			if (this->path && is_inside_tree()) {
+				this->path->path_changed();
+			}
+			return;
+		case NOTIFICATION_EXIT_TREE:
+			this->path = nullptr;
+			return;
+	}
+}
+
+void TerrainModifierPath::_bind_methods() {
+	BIND_HPROPERTY(Variant::OBJECT, curve_left, PROPERTY_HINT_RESOURCE_TYPE, "Curve");
+	BIND_HPROPERTY(Variant::OBJECT, curve_right, PROPERTY_HINT_RESOURCE_TYPE, "Curve");
+}
+
+void TerrainModifierPath::curves_changed() {
+	if (!update_bounds()) {
+		push_changed(get_bounds());
+	}
+	this->lock.lock_exclusive();
+	this->curve_left_buffer = this->curve_left.is_valid() ? this->curve_left->duplicate(true) : nullptr;
+	this->curve_right_buffer = this->curve_right.is_valid() ? this->curve_right->duplicate(true) : nullptr;
+	this->lock.unlock_exclusive();
+}
+
+bool TerrainModifierPath::update_bounds() {
+	Vector2 min{}, max{};
+	this->lock.lock_shared();
+	if (this->points.is_empty() || this->curve_left.is_null()) {
+		Vector3 point{ this->get_thread_safe_global_position() };
+		min.x = point.x;
+		min.y = point.z;
+		max = min;
+	} else {
+		max = min = { this->points[0].x, this->points[0].y };
+		for (Vector3 const &point : this->points) {
+			max.x = max.x > point.x ? max.x : point.x;
+			max.y = max.y > point.z ? max.y : point.z;
+			min.x = min.x < point.x ? min.x : point.x;
+			min.y = min.y < point.z ? min.y : point.z;
+		}
+		float max_distance_left{ this->curve_left->get_max_domain() };
+		float max_distance{ max_distance_left };
+		if (this->curve_right.is_valid()) {
+			float max_distance_right{ this->curve_right->get_max_domain() };
+			max_distance = max_distance_right > max_distance ? max_distance_right : max_distance;
+		}
+		min -= { max_distance, max_distance };
+		max += { max_distance * 2.f, max_distance * 2.f };
+	}
+	Rect2 bounds{ min, max - min };
+	bool const changed{ bounds != get_bounds() };
+	this->lock.unlock_shared();
+	this->lock.lock_exclusive();
+	set_bounds(bounds);
+	this->lock.unlock_exclusive();
+	return changed;
+}
+
+void TerrainModifierPath::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_READY:
+			update_bounds();
+			set_notify_transform(true);
+			return;
+		case NOTIFICATION_TRANSFORM_CHANGED:
+			if (is_inside_tree()) {
+				if (!update_bounds()) {
+					push_changed(get_bounds());
+				}
+			}
+			return;
+		case NOTIFICATION_CHILD_ORDER_CHANGED:
+			path_changed();
+			return;
+	}
+}
+
+float TerrainModifierPath::evaluate_line(Vector3 a, bool a_end, Vector3 b, bool b_end, Vector2 world_coordinate, float &out_dot, float &out_distance, float &out_percentage) {
+	Vector2 a2{ a.x, a.z }, b2{ b.x, b.z };
+	Vector2 const relative_coordinate{ world_coordinate - a2 };
+	Vector2 const difference2{ b2 - a2 };
+	float w{ difference2.normalized().dot(relative_coordinate) / difference2.length() };
+	Vector3 const difference{ b - a };
+	Vector3 const closest_on_line{ a + difference * (w > 0 ? (w < 1 ? w : 1) : 0) };
+	Vector2 const right{ -difference.z, difference.x };
+	out_dot = right.normalized().dot(relative_coordinate);
+	out_distance = world_coordinate.distance_to({ closest_on_line.x, closest_on_line.z });
+	out_percentage = w;
+	return a.y + (b.y - a.y) * w;
+}
+
+float TerrainModifierPath::evaluate_at(Vector2 world_coordinate, float before) {
+	this->lock.lock_shared();
+	if (this->curve_left_buffer.is_null() || this->points.size() <= 1) {
+		this->lock.unlock_shared();
+		return before;
+	}
+	Ref<Curve> right_curve{ this->curve_right_buffer };
+	if (right_curve.is_null()) {
+		right_curve = this->curve_left_buffer;
+	}
+	float out_height{ before };
+	long const count{ this->closed ? this->points.size() : this->points.size() - 1 };
+	for (int i{ 0 }; i < count; i++) {
+		Vector3 const ipos{ this->points[i] };
+		Vector3 const next_pos{ this->points[Math::wrapi(i + 1, 0, this->points.size())] };
+		if (ipos == next_pos) {
+			continue;
+		}
+		float dot, distance, percentage;
+		bool const is_start{ !this->closed && i == 0 }, is_end{ !this->closed && i == count - 1 };
+		float height{ evaluate_line(ipos, is_start, next_pos, is_end, world_coordinate, dot, distance, percentage) };
+		float const left{ this->curve_left_buffer->sample(distance) };
+		float const right{ right_curve->sample(distance) };
+		float const ndot{ dot / distance };
+		float separation{ ndot / 2.f + 0.5f };
+		if (percentage > 0.f && percentage < 1.f) {
+			separation = Math::round(separation);
+		}
+		float const weight{ left * (1.f - separation) + right * separation };
+		float const blended_height{ Math::lerp(out_height, height, weight) };
+		out_height = blended_height;
+	}
+	this->lock.unlock_shared();
+	return out_height;
+}
+
+void TerrainModifierPath::path_changed() {
+	if (!is_inside_tree()) {
+		return;
+	}
+	this->lock.lock_exclusive();
+	this->points.clear();
+	this->min_height = INFINITY;
+	this->max_height = -INFINITY;
+	Vector3 last{ INFINITY, INFINITY, INFINITY };
+	for (Variant var : get_children()) {
+		if (TerrainModifierPathPoint * point{ cast_to<TerrainModifierPathPoint>(var) }) {
+			Vector3 position{ point->get_global_position() };
+			if (position != last) {
+				this->points.push_back(position);
+				if (position.y > this->max_height) {
+					this->max_height = position.y;
+				}
+				if (position.y < this->min_height) {
+					this->min_height = position.y;
+				}
+			}
+		}
+		last = var;
+	}
+	this->lock.unlock_exclusive();
+	if (!update_bounds()) {
+		push_changed(get_bounds());
+	}
+}
+
+PackedStringArray TerrainModifierPath::get_configuration_warnings() const {
+	PackedStringArray warnings{ super_type::get_configuration_warnings() };
+	if (this->curve_left.is_null()) {
+		warnings.push_back("curve_left is invalid, add a valid curve_left");
+	}
+	return warnings;
+}
+
+void TerrainModifierPath::set_curve_left(Ref<Curve> curve) {
+	this->lock.lock_exclusive();
+	if (curve.is_valid() && curve == this->curve_right) {
+		curve = curve->duplicate();
+	}
+	if (Engine::get_singleton()->is_editor_hint()) {
+		if (this->curve_left.is_valid()) {
+			this->curve_left->disconnect_changed(callable_mp(this, &self_type::curves_changed));
+		}
+		if (curve.is_valid()) {
+			curve->connect_changed(callable_mp(this, &self_type::curves_changed));
+		}
+	}
+	this->curve_left = curve;
+	this->lock.unlock_exclusive();
+	if (!curve.is_valid() && this->curve_right.is_valid()) {
+		curve = this->curve_right;
+		set_curve_right(nullptr);
+	} else {
+		curves_changed();
+		update_configuration_warnings();
+	}
+}
+
+Ref<Curve> TerrainModifierPath::get_curve_left() const {
+	return this->curve_left;
+}
+
+void TerrainModifierPath::set_curve_right(Ref<Curve> curve) {
+	this->lock.lock_exclusive();
+	if (curve.is_valid() && curve == this->curve_left) {
+		curve = curve->duplicate();
+	}
+	if (Engine::get_singleton()->is_editor_hint()) {
+		if (this->curve_right.is_valid()) {
+			this->curve_right->disconnect_changed(callable_mp(this, &self_type::curves_changed));
+		}
+		if (curve.is_valid()) {
+			curve->connect_changed(callable_mp(this, &self_type::curves_changed));
+		}
+	}
+	this->curve_right = curve;
+	this->lock.unlock_exclusive();
+	curves_changed();
+	update_configuration_warnings();
+}
+
+Ref<Curve> TerrainModifierPath::get_curve_right() const {
+	return this->curve_right;
+}
+
+void TerrainModifierComposite::update_sub_modifiers() {
+	for (TerrainModifier *mod : this->sub_modifiers) {
+		push_changed(mod->get_bounds());
+	}
+	this->sub_modifiers.clear();
+	for (Variant var : get_children()) {
+		if (TerrainModifier * mod{ cast_to<TerrainModifier>(var) }) {
+			this->sub_modifiers.push_back(mod);
+			mod->set_terrain(get_terrain());
+			push_changed(mod->get_bounds());
+		}
+	}
+}
+
+void TerrainModifierComposite::terrain_changed(Terrain *terrain) {
+	for (TerrainModifier *mod : this->sub_modifiers) {
+		mod->set_terrain(terrain);
+	}
+}
+
+void TerrainModifierComposite::_notification(int what) {
+	switch (what) {
+		default:
+			return;
+		case NOTIFICATION_ENTER_TREE:
+			set_notify_transform(true);
+			if (!is_ready()) {
+				connect(sig_terrain_changed, callable_mp(this, &self_type::terrain_changed));
+			}
+			return;
+		case NOTIFICATION_TRANSFORM_CHANGED:
+			for (TerrainModifier *mod : this->sub_modifiers) {
+				push_changed(mod->get_bounds());
+			}
+			return;
+		case NOTIFICATION_CHILD_ORDER_CHANGED:
+			if (!is_ready()) {
+				return;
+			}
+			// fall through
+		case NOTIFICATION_READY:
+			update_sub_modifiers();
+			return;
+	}
+}
+
+float TerrainModifierComposite::evaluate_at(Vector2 world_coordinate, float before) {
+	float result{ 0.f };
+	for (TerrainModifier *mod : sub_modifiers) {
+		result = mod->evaluate_at(world_coordinate, result);
+	}
+	return result + before;
+}
diff --git a/terrain_modifier.h b/terrain_modifier.h
new file mode 100644
index 0000000..fc318fb
--- /dev/null
+++ b/terrain_modifier.h
@@ -0,0 +1,136 @@
+#pragma once
+
+#include "core/object/object.h"
+#include "core/variant/variant.h"
+#include "macros.h"
+#include "scene/3d/marker_3d.h"
+#include "scene/resources/curve.h"
+#include <cmath>
+class Terrain;
+
+class TerrainModifier : public Marker3D {
+	GDCLASS(TerrainModifier, Marker3D);
+	static void _bind_methods();
+
+protected:
+	void _notification(int what);
+
+public:
+	void push_changed(Rect2 bounds);
+	virtual float evaluate_at(Vector2 world_coordinate, float before);
+
+private:
+	Vector3 thread_safe_global_position{};
+	Terrain *terrain{ nullptr };
+	Rect2 bounds{ { -INFINITY, -INFINITY }, { INFINITY, INFINITY } };
+
+protected:
+	void set_bounds(Rect2 bounds);
+
+public:
+	static String sig_terrain_changed;
+	Rect2 get_bounds() const;
+	Vector3 get_thread_safe_global_position() const;
+	Terrain *get_terrain() const {
+		return this->terrain;
+	}
+	void set_terrain(Terrain *terrain) {
+		this->terrain = terrain;
+		emit_signal(sig_terrain_changed, terrain);
+	}
+};
+
+struct SharedMutex {
+	void lock_shared();
+	void unlock_shared();
+	void lock_exclusive();
+	void unlock_exclusive();
+
+private:
+	Mutex lock{};
+	int shared_count{};
+};
+
+class TerrainModifierDistance : public TerrainModifier {
+	GDCLASS(TerrainModifierDistance, TerrainModifier);
+	static void _bind_methods();
+	void curves_changed();
+	bool update_bounds();
+
+protected:
+	void _notification(int what);
+	float distance_at(Vector2 const &world_coordinate);
+
+public:
+	float evaluate_at(Vector2 world_coordinate, float before) override;
+	PackedStringArray get_configuration_warnings() const override;
+
+private:
+	SharedMutex lock{};
+	Ref<Curve> distance_weight_curve{};
+	Ref<Curve> distance_weight_curve_buffer{};
+
+public:
+	void set_distance_weight_curve(Ref<Curve> curve);
+	Ref<Curve> get_distance_weight_curve() const;
+};
+
+class TerrainModifierPathPoint : public Marker3D {
+	GDCLASS(TerrainModifierPathPoint, Marker3D);
+	static void _bind_methods();
+
+protected:
+	void _notification(int what);
+
+public:
+	class TerrainModifierPath *path{ nullptr };
+};
+
+class TerrainModifierPath : public TerrainModifier {
+	GDCLASS(TerrainModifierPath, TerrainModifier);
+	static void _bind_methods();
+	void curves_changed();
+	bool update_bounds();
+
+protected:
+	void _notification(int what);
+	float evaluate_line(Vector3 a, bool a_end, Vector3 b, bool b_end, Vector2 world_coordinate, float &out_dot, float &out_distance, float &out_percentage);
+
+public:
+	float evaluate_at(Vector2 world_coordinate, float before) override;
+	void path_changed();
+	PackedStringArray get_configuration_warnings() const override;
+
+private:
+	SharedMutex lock{};
+	float min_height{};
+	float max_height{};
+	bool closed{ false };
+	Vector<Vector3> points{};
+	Ref<Curve> curve_left_buffer{};
+	Ref<Curve> curve_left{};
+	Ref<Curve> curve_right_buffer{};
+	Ref<Curve> curve_right{};
+
+public:
+	void set_curve_left(Ref<Curve> curve);
+	Ref<Curve> get_curve_left() const;
+	void set_curve_right(Ref<Curve> curve);
+	Ref<Curve> get_curve_right() const;
+};
+
+class TerrainModifierComposite : public TerrainModifier {
+	GDCLASS(TerrainModifierComposite, TerrainModifier);
+	static void _bind_methods() {}
+	void update_sub_modifiers();
+	void terrain_changed(Terrain *terrain);
+
+protected:
+	void _notification(int what);
+
+public:
+	float evaluate_at(Vector2 world_coordinate, float before) override;
+
+private:
+	Vector<TerrainModifier *> sub_modifiers{};
+};