godot_voxel/terrain/voxel_lod_terrain.cpp

#include "voxel_lod_terrain.h"
#include "../edition/voxel_tool_lod_terrain.h"
#include "../math/rect3i.h"
#include "../meshers/transvoxel/voxel_mesher_transvoxel.h"
#include "../server/voxel_server.h"
#include "../streams/voxel_stream_file.h"
#include "../util/macros.h"
#include "../util/profiling.h"
#include "../util/profiling_clock.h"
#include "../voxel_string_names.h"
#include "voxel_map.h"

#include <core/core_string_names.h>
#include <core/engine.h>
#include <scene/3d/mesh_instance.h>
#include <scene/resources/packed_scene.h>

namespace {

Ref<ArrayMesh> build_mesh(const Vector<Array> surfaces, Mesh::PrimitiveType primitive, int compression_flags,
		Ref<Material> material) {

	Ref<ArrayMesh> mesh;
	mesh.instance();

	unsigned int surface_index = 0;
	for (int i = 0; i < surfaces.size(); ++i) {
		Array surface = surfaces[i];

		if (surface.empty()) {
			continue;
		}

		CRASH_COND(surface.size() != Mesh::ARRAY_MAX);
		if (!is_surface_triangulated(surface)) {
			continue;
		}

		mesh->add_surface_from_arrays(primitive, surface, Array(), compression_flags);
		mesh->surface_set_material(surface_index, material);
		// No multi-material supported yet
		++surface_index;
	}

	if (is_mesh_empty(mesh)) {
		mesh = Ref<Mesh>();
	}

	return mesh;
}

// To use on loaded blocks
static inline void schedule_mesh_update(VoxelBlock *block, std::vector<Vector3i> &blocks_pending_update) {
	if (block->get_mesh_state() != VoxelBlock::MESH_UPDATE_NOT_SENT) {
		if (block->is_visible()) {
			// Schedule an update
			block->set_mesh_state(VoxelBlock::MESH_UPDATE_NOT_SENT);
			blocks_pending_update.push_back(block->position);
		} else {
			// Just mark it as needing update, so the visibility system will schedule its update when needed
			block->set_mesh_state(VoxelBlock::MESH_NEED_UPDATE);
		}
	}
}

struct BeforeUnloadAction {
	std::vector<Ref<ShaderMaterial> > shader_material_pool;
	std::vector<VoxelLodTerrain::BlockToSave> blocks_to_save;

	void operator()(VoxelBlock *block) {
		// Recycle material
		Ref<ShaderMaterial> sm = block->get_shader_material();
		if (sm.is_valid()) {
			shader_material_pool.push_back(sm);
			block->set_shader_material(Ref<ShaderMaterial>());
		}

		// Save if modified
		// TODO Don't ask for save if the stream doesn't support it!
		if (block->is_modified()) {
			//print_line(String("Scheduling save for block {0}").format(varray(block->position.to_vec3())));
			VoxelLodTerrain::BlockToSave b;
			// We don't copy since the block will be unloaded anyways
			b.voxels = block->voxels;
			b.position = block->position;
			b.lod = block->lod_index;
			blocks_to_save.push_back(b);
		}
	}
};

struct ScheduleSaveAction {
	std::vector<VoxelLodTerrain::BlockToSave> blocks_to_save;

	void operator()(VoxelBlock *block) {
		// Save if modified
		// TODO Don't ask for save if the stream doesn't support it!
		if (block->is_modified()) {
			//print_line(String("Scheduling save for block {0}").format(varray(block->position.to_vec3())));
			VoxelLodTerrain::BlockToSave b;

			RWLockRead lock(block->voxels->get_lock());
			b.voxels = block->voxels->duplicate(true);

			b.position = block->position;
			b.lod = block->lod_index;
			blocks_to_save.push_back(b);
			block->set_modified(false);
		}
	}
};

} // namespace

VoxelLodTerrain::VoxelLodTerrain() {
	// Note: don't do anything heavy in the constructor.
	// Godot may create and destroy dozens of instances of all node types on startup,
	// due to how ClassDB gets its default values.

	PRINT_VERBOSE("Construct VoxelLodTerrain");

	set_notify_transform(true);

	// Doing this to setup the defaults
	set_process_mode(_process_mode);

	// Infinite by default
	_bounds_in_voxels = Rect3i::from_center_extents(Vector3i(0), Vector3i(VoxelConstants::MAX_VOLUME_EXTENT));

	_volume_id = VoxelServer::get_singleton()->add_volume(&_reception_buffers, VoxelServer::VOLUME_SPARSE_OCTREE);
	VoxelServer::get_singleton()->set_volume_octree_split_scale(_volume_id, get_lod_split_scale());

	// TODO Being able to set a LOD smaller than the stream is probably a bad idea,
	// Because it prevents edits from propagating up to the last one, they will be left out of sync
	set_lod_count(4);
	set_lod_split_scale(3);

	// For ease of use in editor
	Ref<VoxelMesherTransvoxel> default_mesher;
	default_mesher.instance();
	_mesher = default_mesher;
}

VoxelLodTerrain::~VoxelLodTerrain() {
	PRINT_VERBOSE("Destroy VoxelLodTerrain");

	if (_stream.is_valid()) {
		// Schedule saving of all modified blocks,
		// without copy because we are destroying the map anyways

		flush_pending_lod_edits();

		for (int i = 0; i < _lod_count; ++i) {
			_lods[i].map.for_all_blocks(BeforeUnloadAction{ _shader_material_pool, _blocks_to_save });
		}

		// And flush immediately
		send_block_data_requests();
	}

	VoxelServer::get_singleton()->remove_volume(_volume_id);
}

Ref<Material> VoxelLodTerrain::get_material() const {
	return _material;
}

void VoxelLodTerrain::set_material(Ref<Material> p_material) {
	_material = p_material;
}

unsigned int VoxelLodTerrain::get_block_size() const {
	return _lods[0].map.get_block_size();
}

unsigned int VoxelLodTerrain::get_block_size_pow2() const {
	return _lods[0].map.get_block_size_pow2();
}

void VoxelLodTerrain::set_stream(Ref<VoxelStream> p_stream) {
	if (p_stream == _stream) {
		return;
	}

	_stream = p_stream;

#ifdef TOOLS_ENABLED
	if (_stream.is_valid()) {
		if (Engine::get_singleton()->is_editor_hint()) {
			Ref<Script> script = _stream->get_script();
			if (script.is_valid()) {
				// Safety check. It's too easy to break threads by making a script reload.
				// You can turn it back on, but be careful.
				_run_stream_in_editor = false;
				_change_notify();
			}
		}
	}
#endif

	_on_stream_params_changed();
}

Ref<VoxelStream> VoxelLodTerrain::get_stream() const {
	return _stream;
}

void VoxelLodTerrain::set_generator(Ref<VoxelGenerator> p_generator) {
	if (p_generator == _generator) {
		return;
	}

	_generator = p_generator;

#ifdef TOOLS_ENABLED
	if (_generator.is_valid()) {
		if (Engine::get_singleton()->is_editor_hint()) {
			Ref<Script> script = _generator->get_script();
			if (script.is_valid()) {
				// Safety check. It's too easy to break threads by making a script reload.
				// You can turn it back on, but be careful.
				_run_stream_in_editor = false;
				_change_notify();
			}
		}
	}
#endif

	_on_stream_params_changed();
}

Ref<VoxelGenerator> VoxelLodTerrain::get_generator() const {
	return _generator;
}

void VoxelLodTerrain::set_mesher(Ref<VoxelMesher> p_mesher) {
	if (_mesher == p_mesher) {
		return;
	}

	stop_updater();

	_mesher = p_mesher;

	if (_mesher.is_valid()) {
		start_updater();
		remesh_all_blocks();
	}

	update_configuration_warning();
}

Ref<VoxelMesher> VoxelLodTerrain::get_mesher() const {
	return _mesher;
}

void VoxelLodTerrain::_on_stream_params_changed() {
	stop_streamer();
	stop_updater();

	if (_stream.is_valid()) {
		const int stream_block_size_po2 = _stream->get_block_size_po2();
		_set_block_size_po2(stream_block_size_po2);

		const int stream_lod_count = _stream->get_lod_count();
		_set_lod_count(min(stream_lod_count, get_lod_count()));
	}

	VoxelServer::get_singleton()->set_volume_block_size(_volume_id, get_block_size());

	reset_maps();

	if ((_stream.is_valid() || _generator.is_valid()) &&
			(Engine::get_singleton()->is_editor_hint() == false || _run_stream_in_editor)) {
		start_streamer();
		start_updater();
	}

	// The whole map might change, so make all area dirty
	for (int i = 0; i < get_lod_count(); ++i) {
		Lod &lod = _lods[i];
		lod.last_view_distance_blocks = 0;
	}

	update_configuration_warning();
}

void VoxelLodTerrain::set_block_size_po2(unsigned int p_block_size_po2) {
	ERR_FAIL_COND(p_block_size_po2 < 1);
	ERR_FAIL_COND(p_block_size_po2 > 32);

	unsigned int block_size_po2 = p_block_size_po2;
	Ref<VoxelStreamFile> file_stream = _stream;
	if (file_stream.is_valid()) {
		block_size_po2 = file_stream->get_block_size_po2();
	}

	if (block_size_po2 == get_block_size_pow2()) {
		return;
	}

	_on_stream_params_changed();
}

void VoxelLodTerrain::_set_block_size_po2(int p_block_size_po2) {
	_lods[0].map.create(p_block_size_po2, 0);
}

// Marks intersecting blocks in the area as modified, updates LODs and schedules remeshing.
// The provided box must be at LOD0 coordinates.
void VoxelLodTerrain::post_edit_area(Rect3i p_box) {
	const Rect3i box = p_box.padded(1);
	const Rect3i bbox = box.downscaled(get_block_size());

	bbox.for_each_cell([this](Vector3i block_pos_lod0) {
		post_edit_block_lod0(block_pos_lod0);
	});
}

void VoxelLodTerrain::post_edit_block_lod0(Vector3i block_pos_lod0) {
	Lod &lod0 = _lods[0];
	VoxelBlock *block = lod0.map.get_block(block_pos_lod0);
	ERR_FAIL_COND(block == nullptr);

	block->set_modified(true);

	if (!block->get_needs_lodding()) {
		block->set_needs_lodding(true);
		lod0.blocks_pending_lodding.push_back(block_pos_lod0);
	}
}

Ref<VoxelTool> VoxelLodTerrain::get_voxel_tool() {
	VoxelToolLodTerrain *vt = memnew(VoxelToolLodTerrain(this, _lods[0].map));
	// Set to most commonly used channel on this kind of terrain
	vt->set_channel(VoxelBuffer::CHANNEL_SDF);
	return Ref<VoxelTool>(vt);
}

int VoxelLodTerrain::get_view_distance() const {
	return _view_distance_voxels;
}

// TODO Needs to be clamped dynamically, to avoid the user accidentally setting blowing up memory.
// It used to be clamped to a hardcoded value, but now it may depend on LOD count and boundaries
void VoxelLodTerrain::set_view_distance(int p_distance_in_voxels) {
	ERR_FAIL_COND(p_distance_in_voxels <= 0);
	// Note: this is a hint distance, the terrain will attempt to have this radius filled with loaded voxels.
	// It is possible for blocks to still load beyond that distance.
	_view_distance_voxels = p_distance_in_voxels;
}

void VoxelLodTerrain::start_updater() {
	VoxelServer::get_singleton()->set_volume_mesher(_volume_id, _mesher);
}

void VoxelLodTerrain::stop_updater() {
	struct ResetMeshStateAction {
		void operator()(VoxelBlock *block) {
			if (block->get_mesh_state() == VoxelBlock::MESH_UPDATE_SENT) {
				block->set_mesh_state(VoxelBlock::MESH_UPDATE_NOT_SENT);
			}
		}
	};

	VoxelServer::get_singleton()->set_volume_mesher(_volume_id, Ref<VoxelMesher>());

	_reception_buffers.mesh_output.clear();

	for (unsigned int i = 0; i < _lods.size(); ++i) {
		Lod &lod = _lods[i];
		lod.blocks_pending_update.clear();

		ResetMeshStateAction a;
		lod.map.for_all_blocks(a);
	}
}

void VoxelLodTerrain::start_streamer() {
	VoxelServer::get_singleton()->set_volume_stream(_volume_id, _stream);
	VoxelServer::get_singleton()->set_volume_generator(_volume_id, _generator);
}

void VoxelLodTerrain::stop_streamer() {
	VoxelServer::get_singleton()->set_volume_stream(_volume_id, Ref<VoxelStream>());
	VoxelServer::get_singleton()->set_volume_generator(_volume_id, Ref<VoxelGenerator>());

	for (unsigned int i = 0; i < _lods.size(); ++i) {
		Lod &lod = _lods[i];
		lod.loading_blocks.clear();
		lod.blocks_to_load.clear();
	}

	_reception_buffers.data_output.clear();
}

void VoxelLodTerrain::set_lod_split_scale(float p_lod_split_scale) {
	if (p_lod_split_scale == _lod_split_scale) {
		return;
	}

	_lod_split_scale =
			clamp(p_lod_split_scale, VoxelConstants::MINIMUM_LOD_SPLIT_SCALE, VoxelConstants::MAXIMUM_LOD_SPLIT_SCALE);

	for (Map<Vector3i, OctreeItem>::Element *E = _lod_octrees.front(); E; E = E->next()) {
		OctreeItem &item = E->value();
		item.octree.set_split_scale(_lod_split_scale);

		// Because `set_split_scale` may clamp it...
		_lod_split_scale = item.octree.get_split_scale();
	}

	VoxelServer::get_singleton()->set_volume_octree_split_scale(_volume_id, get_lod_split_scale());
}

float VoxelLodTerrain::get_lod_split_scale() const {
	return _lod_split_scale;
}

void VoxelLodTerrain::set_lod_count(int p_lod_count) {
	ERR_FAIL_COND(p_lod_count >= (int)VoxelConstants::MAX_LOD);
	ERR_FAIL_COND(p_lod_count < 1);

	if (get_lod_count() != p_lod_count) {
		_set_lod_count(p_lod_count);
	}
}

void VoxelLodTerrain::_set_lod_count(int p_lod_count) {
	CRASH_COND(p_lod_count >= (int)VoxelConstants::MAX_LOD);
	CRASH_COND(p_lod_count < 1);

	_lod_count = p_lod_count;

	LodOctree::NoDestroyAction nda;

	for (Map<Vector3i, OctreeItem>::Element *E = _lod_octrees.front(); E; E = E->next()) {
		OctreeItem &item = E->value();
		item.octree.create_from_lod_count(get_block_size(), p_lod_count, nda);
	}

	// Not entirely required, but changing LOD count at runtime is rarely needed
	reset_maps();
}

void VoxelLodTerrain::reset_maps() {
	// Clears all blocks and reconfigures maps to account for new LOD count and block sizes

	// Don't reset while streaming, the result can be dirty?
	//CRASH_COND(_stream_thread != nullptr);

	for (int lod_index = 0; lod_index < (int)_lods.size(); ++lod_index) {
		Lod &lod = _lods[lod_index];

		// Instance new maps if we have more lods, or clear them otherwise
		if (lod_index < get_lod_count()) {
			lod.map.create(get_block_size_pow2(), lod_index);
			lod.blocks_to_load.clear();
			lod.last_view_distance_blocks = 0;

		} else {
			lod.map.clear();
		}
	}

	// Reset previous state caches to force rebuilding the view area
	_last_octree_region_box = Rect3i();
	_lod_octrees.clear();
}

int VoxelLodTerrain::get_lod_count() const {
	return _lod_count;
}

void VoxelLodTerrain::set_generate_collisions(bool enabled) {
	_generate_collisions = enabled;
}

void VoxelLodTerrain::set_collision_lod_count(int lod_count) {
	_collision_lod_count = CLAMP(lod_count, -1, get_lod_count());
}

int VoxelLodTerrain::get_collision_lod_count() const {
	return _collision_lod_count;
}

int VoxelLodTerrain::get_block_region_extent() const {
	return VoxelServer::get_octree_lod_block_region_extent(_lod_split_scale);
}

Vector3 VoxelLodTerrain::voxel_to_block_position(Vector3 vpos, int lod_index) const {
	ERR_FAIL_COND_V(lod_index < 0, Vector3());
	ERR_FAIL_COND_V(lod_index >= get_lod_count(), Vector3());
	const Lod &lod = _lods[lod_index];
	Vector3i bpos = lod.map.voxel_to_block(Vector3i(vpos)) >> lod_index;
	return bpos.to_vec3();
}

void VoxelLodTerrain::set_process_mode(ProcessMode mode) {
	_process_mode = mode;
	set_process(_process_mode == PROCESS_MODE_IDLE);
	set_physics_process(_process_mode == PROCESS_MODE_PHYSICS);
}

void VoxelLodTerrain::_notification(int p_what) {
	switch (p_what) {
		// TODO Should use NOTIFICATION_INTERNAL_PROCESS instead?
		case NOTIFICATION_PROCESS:
			if (_process_mode == PROCESS_MODE_IDLE) {
				// Can't do that in enter tree because Godot is "still setting up children".
				// Can't do that in ready either because Godot says node state is locked.
				// This hack is quite miserable.
				VoxelServerUpdater::ensure_existence(get_tree());
				_process();
			}
			break;

		// TODO Should use NOTIFICATION_INTERNAL_PHYSICS_PROCESS instead?
		case NOTIFICATION_PHYSICS_PROCESS:
			if (_process_mode == PROCESS_MODE_PHYSICS) {
				// Can't do that in enter tree because Godot is "still setting up children".
				// Can't do that in ready either because Godot says node state is locked.
				// This hack is quite miserable.
				VoxelServerUpdater::ensure_existence(get_tree());
				_process();
				break;
			}

		case NOTIFICATION_EXIT_TREE:
			break;

		case NOTIFICATION_ENTER_WORLD: {
			World *world = *get_world();
			for (unsigned int lod_index = 0; lod_index < _lods.size(); ++lod_index) {
				_lods[lod_index].map.for_all_blocks([world](VoxelBlock *block) {
					block->set_world(world);
				});
			}
#ifdef TOOLS_ENABLED
			if (is_showing_gizmos()) {
				_debug_renderer.set_world(is_visible_in_tree() ? world : nullptr);
			}
#endif
		} break;

		case NOTIFICATION_EXIT_WORLD: {
			for (unsigned int lod_index = 0; lod_index < _lods.size(); ++lod_index) {
				_lods[lod_index].map.for_all_blocks([](VoxelBlock *block) {
					block->set_world(nullptr);
				});
			}
#ifdef TOOLS_ENABLED
			_debug_renderer.set_world(nullptr);
#endif
		} break;

		case NOTIFICATION_VISIBILITY_CHANGED: {
			const bool visible = is_visible();
			for (unsigned int lod_index = 0; lod_index < _lods.size(); ++lod_index) {
				_lods[lod_index].map.for_all_blocks([visible](VoxelBlock *block) {
					block->set_parent_visible(visible);
				});
			}
#ifdef TOOLS_ENABLED
			if (is_showing_gizmos()) {
				_debug_renderer.set_world(is_visible_in_tree() ? *get_world() : nullptr);
			}
#endif
		} break;

		case NOTIFICATION_TRANSFORM_CHANGED: {
			VOXEL_PROFILE_SCOPE_NAMED("VoxelLodTerrain::NOTIFICATION_TRANSFORM_CHANGED");

			const Transform transform = get_global_transform();
			VoxelServer::get_singleton()->set_volume_transform(_volume_id, transform);

			if (!is_inside_tree()) {
				// The transform and other properties can be set by the scene loader,
				// before we enter the tree
				return;
			}

			for (unsigned int lod_index = 0; lod_index < _lods.size(); ++lod_index) {
				_lods[lod_index].map.for_all_blocks([&transform](VoxelBlock *block) {
					block->set_parent_transform(transform);
				});
			}
		} break;

		default:
			break;
	}
}

Vector3 VoxelLodTerrain::get_local_viewer_pos() const {
	Vector3 pos = (_lods[0].last_viewer_block_pos << _lods[0].map.get_block_size_pow2()).to_vec3();

	// TODO Support for multiple viewers, this is a placeholder implementation
	VoxelServer::get_singleton()->for_each_viewer([&pos](const VoxelServer::Viewer &viewer, uint32_t viewer_id) {
		pos = viewer.world_position;
	});

	const Transform world_to_local = get_global_transform().affine_inverse();
	pos = world_to_local.xform(pos);
	return pos;
}

void VoxelLodTerrain::try_schedule_loading_with_neighbors(const Vector3i &p_bpos, int lod_index) {
	Lod &lod = _lods[lod_index];

	const int p = lod.map.get_block_size_pow2() + lod_index;

	const int bound_min_x = _bounds_in_voxels.pos.x >> p;
	const int bound_min_y = _bounds_in_voxels.pos.y >> p;
	const int bound_min_z = _bounds_in_voxels.pos.z >> p;
	const int bound_max_x = (_bounds_in_voxels.pos.x + _bounds_in_voxels.size.x) >> p;
	const int bound_max_y = (_bounds_in_voxels.pos.x + _bounds_in_voxels.size.x) >> p;
	const int bound_max_z = (_bounds_in_voxels.pos.x + _bounds_in_voxels.size.x) >> p;

	const int min_x = max(p_bpos.x - 1, bound_min_x);
	const int min_y = max(p_bpos.y - 1, bound_min_y);
	const int min_z = max(p_bpos.z - 1, bound_min_z);
	const int max_x = min(p_bpos.x + 2, bound_max_x);
	const int max_y = min(p_bpos.y + 2, bound_max_y);
	const int max_z = min(p_bpos.z + 2, bound_max_z);

	Vector3i bpos;
	for (bpos.y = min_y; bpos.y < max_y; ++bpos.y) {
		for (bpos.z = min_z; bpos.z < max_z; ++bpos.z) {
			for (bpos.x = min_x; bpos.x < max_x; ++bpos.x) {
				VoxelBlock *block = lod.map.get_block(bpos);

				if (block == nullptr) {
					if (!lod.loading_blocks.has(bpos)) {
						lod.blocks_to_load.push_back(bpos);
						lod.loading_blocks.insert(bpos);
					}
				}
			}
		}
	}
}

bool VoxelLodTerrain::is_block_surrounded(const Vector3i &p_bpos, int lod_index, const VoxelMap &map) const {
	const int p = map.get_block_size_pow2() + lod_index;

	const int bound_min_x = _bounds_in_voxels.pos.x >> p;
	const int bound_min_y = _bounds_in_voxels.pos.y >> p;
	const int bound_min_z = _bounds_in_voxels.pos.z >> p;
	const int bound_max_x = (_bounds_in_voxels.pos.x + _bounds_in_voxels.size.x) >> p;
	const int bound_max_y = (_bounds_in_voxels.pos.x + _bounds_in_voxels.size.x) >> p;
	const int bound_max_z = (_bounds_in_voxels.pos.x + _bounds_in_voxels.size.x) >> p;

	const int min_x = max(p_bpos.x - 1, bound_min_x);
	const int min_y = max(p_bpos.y - 1, bound_min_y);
	const int min_z = max(p_bpos.z - 1, bound_min_z);
	const int max_x = min(p_bpos.x + 2, bound_max_x);
	const int max_y = min(p_bpos.y + 2, bound_max_y);
	const int max_z = min(p_bpos.z + 2, bound_max_z);

	Vector3i bpos;
	for (bpos.y = min_y; bpos.y < max_y; ++bpos.y) {
		for (bpos.z = min_z; bpos.z < max_z; ++bpos.z) {
			for (bpos.x = min_x; bpos.x < max_x; ++bpos.x) {
				if (bpos != p_bpos && !map.has_block(bpos)) {
					return false;
				}
			}
		}
	}
	return true;
}

bool VoxelLodTerrain::check_block_loaded_and_updated(const Vector3i &p_bpos, int lod_index) {
	Lod &lod = _lods[lod_index];
	VoxelBlock *block = lod.map.get_block(p_bpos);
	if (block == nullptr) {
		try_schedule_loading_with_neighbors(p_bpos, lod_index);
		return false;
	}
	return check_block_mesh_updated(block);
}

bool VoxelLodTerrain::check_block_mesh_updated(VoxelBlock *block) {
	VOXEL_PROFILE_SCOPE();
	CRASH_COND(block == nullptr);
	Lod &lod = _lods[block->lod_index];

	switch (block->get_mesh_state()) {
		case VoxelBlock::MESH_NEVER_UPDATED:
		case VoxelBlock::MESH_NEED_UPDATE:
			if (is_block_surrounded(block->position, block->lod_index, lod.map)) {
				lod.blocks_pending_update.push_back(block->position);
				block->set_mesh_state(VoxelBlock::MESH_UPDATE_NOT_SENT);
			} else {
				try_schedule_loading_with_neighbors(block->position, block->lod_index);
			}
			return false;

		case VoxelBlock::MESH_UPDATE_NOT_SENT:
		case VoxelBlock::MESH_UPDATE_SENT:
			return false;

		case VoxelBlock::MESH_UP_TO_DATE:
			return true;

		default:
			CRASH_NOW();
			break;
	}

	return true;
}

void VoxelLodTerrain::send_block_data_requests() {
	// Blocks to load
	for (int lod_index = 0; lod_index < get_lod_count(); ++lod_index) {
		Lod &lod = _lods[lod_index];

		for (unsigned int i = 0; i < lod.blocks_to_load.size(); ++i) {
			const Vector3i block_pos = lod.blocks_to_load[i];
			VoxelServer::get_singleton()->request_block_load(_volume_id, block_pos, lod_index);
		}

		lod.blocks_to_load.clear();
	}

	// Blocks to save
	for (unsigned int i = 0; i < _blocks_to_save.size(); ++i) {
		PRINT_VERBOSE(String("Requesting save of block {0} lod {1}")
							  .format(varray(_blocks_to_save[i].position.to_vec3(), _blocks_to_save[i].lod)));
		const BlockToSave &b = _blocks_to_save[i];
		VoxelServer::get_singleton()->request_block_save(_volume_id, b.voxels, b.position, b.lod);
	}

	_blocks_to_save.clear();
}

void VoxelLodTerrain::_process() {
	VOXEL_PROFILE_SCOPE();

	if (get_lod_count() == 0) {
		// If there isn't a LOD 0, there is nothing to load
		return;
	}

	// Get viewer location in voxel space
	const Vector3 viewer_pos = get_local_viewer_pos();

	_stats.dropped_block_loads = 0;
	_stats.dropped_block_meshs = 0;
	_stats.blocked_lods = 0;

	// Here we go...

	// Update pending LOD data modifications due to edits.
	// These are deferred from edits so we can batch them.
	// It has to happen first because blocks can be unloaded afterwards.
	flush_pending_lod_edits();

	ProfilingClock profiling_clock;

	// Unload blocks falling out of block region extent
	// TODO Obsoleted by octree grid?
	{
		VOXEL_PROFILE_SCOPE();
		// TODO Could it actually be enough to have a rolling update on all blocks?

		// This should be the same distance relatively to each LOD
		const int block_region_extent = get_block_region_extent();

		// Ignore largest lod because it can extend a little beyond due to the view distance setting.
		// Instead, those blocks are unloaded by the octree forest management.
		// Iterating from big to small LOD so we can exit earlier if bounds don't intersect.
		for (int lod_index = get_lod_count() - 2; lod_index >= 0; --lod_index) {
			VOXEL_PROFILE_SCOPE();
			Lod &lod = _lods[lod_index];

			// Each LOD keeps a box of loaded blocks, and only some of the blocks will get polygonized.
			// The player can edit them so changes can be propagated to lower lods.

			unsigned int block_size_po2 = _lods[0].map.get_block_size_pow2() + lod_index;
			Vector3i viewer_block_pos_within_lod = VoxelMap::voxel_to_block_b(viewer_pos, block_size_po2);

			const Rect3i bounds_in_blocks = Rect3i(
					_bounds_in_voxels.pos >> block_size_po2,
					_bounds_in_voxels.size >> block_size_po2);

			const Rect3i new_box =
					Rect3i::from_center_extents(viewer_block_pos_within_lod, Vector3i(block_region_extent));
			const Rect3i prev_box =
					Rect3i::from_center_extents(lod.last_viewer_block_pos, Vector3i(lod.last_view_distance_blocks));

			if (!new_box.intersects(bounds_in_blocks) && !prev_box.intersects(bounds_in_blocks)) {
				// If this box doesn't intersect either now or before, there is no chance a smaller one will
				break;
			}

			// Eliminate pending blocks that aren't needed

			// This vector must be empty at this point.
			// Let's assert so it will pop on your face the day that assumption changes
			CRASH_COND(!lod.blocks_to_load.empty());

			if (prev_box != new_box) {
				VOXEL_PROFILE_SCOPE();
				prev_box.difference(new_box, [this, lod_index](Rect3i out_of_range_box) {
					out_of_range_box.for_each_cell([=](Vector3i pos) {
						//print_line(String("Immerge {0}").format(varray(pos.to_vec3())));
						immerge_block(pos, lod_index);
					});
				});
			}

			// Cancel block updates that are not within the padded region (since neighbors are always required to remesh)
			const Rect3i padded_new_box = new_box.padded(-1);
			{
				VOXEL_PROFILE_SCOPE();
				unordered_remove_if(lod.blocks_pending_update, [&lod, padded_new_box](Vector3i bpos) {
					if (padded_new_box.contains(bpos)) {
						return false;
					} else {
						VoxelBlock *block = lod.map.get_block(bpos);
						if (block != nullptr) {
							block->set_mesh_state(VoxelBlock::MESH_NEED_UPDATE);
						}
						return true;
					}
				});
			}

			lod.last_viewer_block_pos = viewer_block_pos_within_lod;
			lod.last_view_distance_blocks = block_region_extent;
		}
	}

	// Create and remove octrees in a grid around the viewer
	{
		VOXEL_PROFILE_SCOPE();
		// TODO Investigate if multi-octree can produce cracks in the terrain (so far I haven't noticed)

		const unsigned int octree_size_po2 = get_block_size_pow2() + get_lod_count() - 1;
		const unsigned int octree_size = 1 << octree_size_po2;
		const unsigned int octree_region_extent = 1 + _view_distance_voxels / (1 << octree_size_po2);

		const Vector3i viewer_octree_pos = (Vector3i(viewer_pos) + Vector3i(octree_size / 2)) >> octree_size_po2;

		const Rect3i bounds_in_octrees = _bounds_in_voxels.downscaled(octree_size);

		const Rect3i new_box = Rect3i::from_center_extents(viewer_octree_pos, Vector3i(octree_region_extent))
									   .clipped(bounds_in_octrees);
		const Rect3i prev_box = _last_octree_region_box;

		if (new_box != prev_box) {
			VOXEL_PROFILE_SCOPE();

			struct CleanOctreeAction {
				VoxelLodTerrain *self;
				Vector3i block_offset_lod0;

				void operator()(Vector3i node_pos, unsigned int lod_index) {
					Lod &lod = self->_lods[lod_index];

					Vector3i bpos = node_pos + (block_offset_lod0 >> lod_index);

					VoxelBlock *block = lod.map.get_block(bpos);
					if (block) {
						block->set_visible(false);
					}
				}
			};

			struct ExitAction {
				VoxelLodTerrain *self;
				void operator()(const Vector3i &pos) {

					Map<Vector3i, OctreeItem>::Element *E = self->_lod_octrees.find(pos);
					if (E == nullptr) {
						return;
					}

					OctreeItem &item = E->value();
					Vector3i block_pos_maxlod = E->key();

					int last_lod_index = self->get_lod_count() - 1;

					// We just drop the octree and hide blocks it was considering as visible.
					// Normally such octrees shouldn't bee too deep as they will likely be at the edge
					// of the loaded area, unless the player teleported far away.
					CleanOctreeAction a;
					a.self = self;
					a.block_offset_lod0 = block_pos_maxlod << last_lod_index;
					item.octree.clear(a);

					self->_lod_octrees.erase(E);

					// Immerge last lod from here, as it may extend a bit further than the others
					self->immerge_block(pos, last_lod_index);
				}
			};

			struct EnterAction {
				VoxelLodTerrain *self;
				int block_size;
				void operator()(const Vector3i &pos) {
					// That's a new cell we are entering, shouldn't be anything there
					CRASH_COND(self->_lod_octrees.has(pos));

					// Create new octree
					// TODO Use ObjectPool to store them, deletion won't be cheap
					Map<Vector3i, OctreeItem>::Element *E = self->_lod_octrees.insert(pos, OctreeItem());
					CRASH_COND(E == nullptr);
					OctreeItem &item = E->value();
					LodOctree::NoDestroyAction nda;
					item.octree.create_from_lod_count(block_size, self->get_lod_count(), nda);
					item.octree.set_split_scale(self->_lod_split_scale);
				}
			};

			ExitAction exit_action;
			exit_action.self = this;

			EnterAction enter_action;
			enter_action.self = this;
			enter_action.block_size = get_block_size();

			prev_box.difference(new_box, [exit_action](Rect3i out_of_range_box) {
				out_of_range_box.for_each_cell(exit_action);
			});

			new_box.difference(prev_box, [enter_action](Rect3i box_to_load) {
				box_to_load.for_each_cell(enter_action);
			});
		}

		_last_octree_region_box = new_box;
	}

	CRASH_COND(_blocks_pending_transition_update.size() != 0);

	// Find which blocks we need to load and see, within each octree
	{
		VOXEL_PROFILE_SCOPE();

		// TODO Maintain a vector to make iteration faster?
		for (Map<Vector3i, OctreeItem>::Element *E = _lod_octrees.front(); E; E = E->next()) {
			VOXEL_PROFILE_SCOPE();

			OctreeItem &item = E->value();
			Vector3i block_pos_maxlod = E->key();
			Vector3i block_offset_lod0 = block_pos_maxlod << (get_lod_count() - 1);

			struct OctreeActions {
				VoxelLodTerrain *self = nullptr;
				Vector3i block_offset_lod0;
				unsigned int blocked_count = 0;

				void create_child(Vector3i node_pos, int lod_index) {
					Lod &lod = self->_lods[lod_index];
					Vector3i bpos = node_pos + (block_offset_lod0 >> lod_index);
					VoxelBlock *block = lod.map.get_block(bpos);

					// Never show a child that hasn't been meshed
					CRASH_COND(block == nullptr);
					CRASH_COND(block->get_mesh_state() != VoxelBlock::MESH_UP_TO_DATE);

					block->set_visible(true);
					self->add_transition_update(block);
					self->add_transition_updates_around(bpos, lod_index);
				}

				void destroy_child(Vector3i node_pos, int lod_index) {
					Lod &lod = self->_lods[lod_index];
					Vector3i bpos = node_pos + (block_offset_lod0 >> lod_index);
					VoxelBlock *block = lod.map.get_block(bpos);

					if (block) {
						block->set_visible(false);
						self->add_transition_updates_around(bpos, lod_index);
					}
				}

				void show_parent(Vector3i node_pos, int lod_index) {
					Lod &lod = self->_lods[lod_index];
					Vector3i bpos = node_pos + (block_offset_lod0 >> lod_index);
					VoxelBlock *block = lod.map.get_block(bpos);

					// If we teleport far away, the area we were in is going to merge,
					// and blocks may have been unloaded completely.
					// So in that case it's normal to not find any block.
					// Otherwise, there must always be a visible parent in the end, unless the octree vanished.
					if (block != nullptr && block->get_mesh_state() == VoxelBlock::MESH_UP_TO_DATE) {
						block->set_visible(true);
						self->add_transition_update(block);
						self->add_transition_updates_around(bpos, lod_index);
					}
				}

				void hide_parent(Vector3i node_pos, int lod_index) {
					destroy_child(node_pos, lod_index); // Same
				}

				bool can_create_root(int lod_index) {
					Vector3i offset = block_offset_lod0 >> lod_index;
					return self->check_block_loaded_and_updated(offset, lod_index);
				}

				bool can_split(Vector3i node_pos, int child_lod_index) {
					Vector3i offset = block_offset_lod0 >> child_lod_index;
					bool can = true;

					// Can only subdivide if higher detail meshes are ready to be shown, otherwise it will produce holes
					for (int i = 0; i < 8; ++i) {

						// Get block pos local-to-region
						Vector3i child_pos = LodOctree::get_child_position(node_pos, i);

						// Convert to local-to-terrain
						child_pos += offset;

						// We have to ping ALL children, because the reason we are here is we want them loaded
						can &= self->check_block_loaded_and_updated(child_pos, child_lod_index);
					}

					if (!can) {
						++blocked_count;
					}

					return can;
				}

				bool can_join(Vector3i node_pos, int parent_lod_index) {
					// Can only unsubdivide if the parent mesh is ready
					Lod &lod = self->_lods[parent_lod_index];

					Vector3i bpos = node_pos + (block_offset_lod0 >> parent_lod_index);
					VoxelBlock *block = lod.map.get_block(bpos);

					if (block == nullptr) {
						// The block got unloaded. Exceptionally, we can join.
						// There will always be a grand-parent because we never destroy them when they split,
						// and we never create a child without creating a parent first.
						return true;
					}

					// The block is loaded but the mesh isn't up to date, we need to ping and wait.
					bool can = self->check_block_mesh_updated(block);

					if (!can) {
						++blocked_count;
					}

					return can;
				}
			};

			OctreeActions octree_actions;
			octree_actions.self = this;
			octree_actions.block_offset_lod0 = block_offset_lod0;

			Vector3 relative_viewer_pos = viewer_pos - get_block_size() * block_offset_lod0.to_vec3();
			item.octree.update(relative_viewer_pos, octree_actions);

			// Ideally, this stat should stabilize to zero.
			// If not, something in block management prevents LODs from properly show up and should be fixed.
			_stats.blocked_lods += octree_actions.blocked_count;
		}

		{
			VOXEL_PROFILE_SCOPE();
			process_transition_updates();
		}
	}

	CRASH_COND(_blocks_pending_transition_update.size() != 0);

	_stats.time_detect_required_blocks = profiling_clock.restart();

	const bool stream_enabled = (_stream.is_valid() || _generator.is_valid()) &&
								(Engine::get_singleton()->is_editor_hint() == false || _run_stream_in_editor);

	// It's possible the user didn't set a stream yet, or it is turned off
	if (stream_enabled) {
		send_block_data_requests();
	}

	_stats.time_request_blocks_to_load = profiling_clock.restart();

	// Get block loading responses
	// Note: if block loading is too fast, this can cause stutters.
	// It should only happen on first load, though.
	{
		VOXEL_PROFILE_SCOPE();

		for (size_t reception_index = 0; reception_index < _reception_buffers.data_output.size(); ++reception_index) {
			VOXEL_PROFILE_SCOPE();
			const VoxelServer::BlockDataOutput &ob = _reception_buffers.data_output[reception_index];

			if (ob.type == VoxelServer::BlockDataOutput::TYPE_SAVE) {
				// That's a save confirmation event.
				// Note: in the future, if blocks don't get copied before being sent for saving,
				// we will need to use block versionning to know when we can reset the `modified` flag properly

				// TODO Now that's the case. Use version? Or just keep copying?
				continue;
			}

			if (ob.lod >= get_lod_count()) {
				// That block was requested at a time where LOD was higher... drop it
				++_stats.dropped_block_loads;
				continue;
			}

			Lod &lod = _lods[ob.lod];

			{
				Set<Vector3i>::Element *E = lod.loading_blocks.find(ob.position);
				if (E == nullptr) {
					// That block was not requested, or is no longer needed. drop it...
					++_stats.dropped_block_loads;
					continue;
				}

				lod.loading_blocks.erase(E);
			}

			if (ob.dropped) {
				// That block was dropped by the data loader thread, but we were still expecting it...
				// This is most likely caused by the loader not keeping up with the speed at which the player is moving.
				// We should recover with the removal from `loading_blocks` so it will be re-queried again later...

				//				print_line(String("Received a block loading drop while we were still expecting it: lod{0} ({1}, {2}, {3})")
				//								   .format(varray(ob.lod, ob.position.x, ob.position.y, ob.position.z)));

				++_stats.dropped_block_loads;
				continue;
			}

			if (ob.voxels->get_size() != Vector3i(lod.map.get_block_size())) {
				// Voxel block size is incorrect, drop it
				ERR_PRINT("Block size obtained from stream is different from expected size");
				++_stats.dropped_block_loads;
				continue;
			}

			// Store buffer
			VoxelBlock *block = lod.map.set_block_buffer(ob.position, ob.voxels);
			//print_line(String("Adding block {0} at lod {1}").format(varray(eo.block_position.to_vec3(), eo.lod)));
			// The block will be made visible and meshed only by LodOctree
			block->set_visible(false);
			block->set_parent_visible(is_visible());
			block->set_world(get_world());

			Ref<ShaderMaterial> shader_material = _material;
			if (shader_material.is_valid() && block->get_shader_material().is_null()) {
				VOXEL_PROFILE_SCOPE();

				// Pooling shader materials is necessary for now, to avoid stuttering in the editor.
				// Due to a signal used to keep the inspector up to date, even though these
				// material copies will never be seen in the inspector
				// See https://github.com/godotengine/godot/issues/34741
				Ref<ShaderMaterial> sm;
				if (_shader_material_pool.size() > 0) {
					sm = _shader_material_pool.back();
					// The joys of pooling materials
					sm->set_shader_param(VoxelStringNames::get_singleton()->u_transition_mask, 0);
					_shader_material_pool.pop_back();
				} else {
					sm = shader_material->duplicate(false);
				}

				// Set individual shader material, because each block can have dynamic parameters,
				// used to smooth seams without re-uploading meshes and allow to implement LOD fading
				block->set_shader_material(sm);
			}
		}
	}

	_stats.time_process_load_responses = profiling_clock.restart();

	// Send mesh updates
	{
		VOXEL_PROFILE_SCOPE();

		for (int lod_index = 0; lod_index < get_lod_count(); ++lod_index) {
			VOXEL_PROFILE_SCOPE();
			Lod &lod = _lods[lod_index];

			for (unsigned int bi = 0; bi < lod.blocks_pending_update.size(); ++bi) {
				VOXEL_PROFILE_SCOPE();
				const Vector3i block_pos = lod.blocks_pending_update[bi];

				VoxelBlock *block = lod.map.get_block(block_pos);
				CRASH_COND(block == nullptr);
				// All blocks we get here must be in the scheduled state
				CRASH_COND(block->get_mesh_state() != VoxelBlock::MESH_UPDATE_NOT_SENT);

				// Get block and its neighbors
				VoxelServer::BlockMeshInput mesh_request;
				mesh_request.position = block_pos;
				mesh_request.lod = lod_index;
				for (unsigned int i = 0; i < Cube::MOORE_AREA_3D_COUNT; ++i) {
					const Vector3i npos = block_pos + Cube::g_ordered_moore_area_3d[i];
					VoxelBlock *nblock = lod.map.get_block(npos);
					// The block can actually be null on some occasions. Not sure yet if it's that bad
					//CRASH_COND(nblock == nullptr);
					if (nblock == nullptr) {
						continue;
					}
					mesh_request.blocks[i] = nblock->voxels;
				}

				VoxelServer::get_singleton()->request_block_mesh(_volume_id, mesh_request);

				block->set_mesh_state(VoxelBlock::MESH_UPDATE_SENT);
			}

			lod.blocks_pending_update.clear();
		}
	}

	_stats.time_request_blocks_to_update = profiling_clock.restart();

	// Receive mesh updates
	{
		VOXEL_PROFILE_SCOPE_NAMED("Receive mesh updates");

		// Allocate milliseconds max to upload meshes
		const OS &os = *OS::get_singleton();
		const uint32_t timeout = os.get_ticks_msec() + VoxelConstants::MAIN_THREAD_MESHING_BUDGET_MS;

		const Transform global_transform = get_global_transform();

		// The following is done on the main thread because Godot doesn't really support multithreaded Mesh allocation.
		// This also proved to be very slow compared to the meshing process itself...
		// hopefully Vulkan will allow us to upload graphical resources without stalling rendering as they upload?

		size_t queue_index = 0;
		for (; queue_index < _reception_buffers.mesh_output.size() && os.get_ticks_msec() < timeout; ++queue_index) {
			VOXEL_PROFILE_SCOPE();
			const VoxelServer::BlockMeshOutput &ob = _reception_buffers.mesh_output[queue_index];

			if (ob.lod >= get_lod_count()) {
				// Sorry, LOD configuration changed, drop that mesh
				++_stats.dropped_block_meshs;
				continue;
			}

			Lod &lod = _lods[ob.lod];

			VoxelBlock *block = lod.map.get_block(ob.position);
			if (block == nullptr) {
				// That block is no longer loaded, drop the result
				++_stats.dropped_block_meshs;
				continue;
			}

			if (ob.type == VoxelServer::BlockMeshOutput::TYPE_DROPPED) {
				// That block is loaded, but its meshing request was dropped.
				// TODO Not sure what to do in this case, the code sending update queries has to be tweaked
				PRINT_VERBOSE("Received a block mesh drop while we were still expecting it");
				++_stats.dropped_block_meshs;
				continue;
			}

			if (block->get_mesh_state() == VoxelBlock::MESH_UPDATE_SENT) {
				block->set_mesh_state(VoxelBlock::MESH_UP_TO_DATE);
			}

			const VoxelMesher::Output mesh_data = ob.surfaces;

			Ref<ArrayMesh> mesh = build_mesh(
					mesh_data.surfaces,
					mesh_data.primitive_type,
					mesh_data.compression_flags,
					_material);

			bool has_collision = _generate_collisions;
			if (has_collision && _collision_lod_count != -1) {
				has_collision = ob.lod < _collision_lod_count;
			}

			block->set_mesh(mesh);
			if (has_collision) {
				block->set_collision_mesh(mesh_data.surfaces, get_tree()->is_debugging_collisions_hint(), this);
			}

			{
				VOXEL_PROFILE_SCOPE();
				for (unsigned int dir = 0; dir < mesh_data.transition_surfaces.size(); ++dir) {

					Ref<ArrayMesh> transition_mesh = build_mesh(
							mesh_data.transition_surfaces[dir],
							mesh_data.primitive_type,
							mesh_data.compression_flags,
							_material);

					block->set_transition_mesh(transition_mesh, dir);
				}
			}

			block->set_parent_transform(global_transform);
		}

		{
			VOXEL_PROFILE_SCOPE();
			shift_up(_reception_buffers.mesh_output, queue_index);
		}

		_stats.remaining_main_thread_blocks = (int)_reception_buffers.mesh_output.size();
	}

	_stats.time_process_update_responses = profiling_clock.restart();

#ifdef TOOLS_ENABLED
	if (is_showing_gizmos() && is_visible_in_tree()) {
		update_gizmos();
	}
#endif
}

void VoxelLodTerrain::flush_pending_lod_edits() {
	// Propagates edits performed so far to other LODs.
	// These LODs must be currently in memory, otherwise terrain data will miss it.
	// This is currently ensured by the fact we load blocks in a "pyramidal" way,
	// i.e there is no way for a block to be loaded if its parent LOD isn't loaded already.
	// In the future we may implement storing of edits to be applied later if blocks can't be found.

	//ProfilingClock profiling_clock;

	// Make sure LOD0 gets updates even if _lod_count is 1
	Lod &lod0 = _lods[0];
	for (unsigned int i = 0; i < lod0.blocks_pending_lodding.size(); ++i) {
		const Vector3i bpos = lod0.blocks_pending_lodding[i];
		VoxelBlock *block = lod0.map.get_block(bpos);
		block->set_needs_lodding(false);
		schedule_mesh_update(block, lod0.blocks_pending_update);
	}

	const int half_bs = get_block_size() >> 1;

	// Process downscales upwards in pairs of consecutive LODs.
	// This ensures we don't process multiple times the same blocks.
	// Only LOD0 is editable at the moment, so we'll downscale from there
	for (int dst_lod_index = 1; dst_lod_index < _lod_count; ++dst_lod_index) {
		Lod &src_lod = _lods[dst_lod_index - 1];
		Lod &dst_lod = _lods[dst_lod_index];

		for (unsigned int i = 0; i < src_lod.blocks_pending_lodding.size(); ++i) {
			const Vector3i src_bpos = src_lod.blocks_pending_lodding[i];
			const Vector3i dst_bpos = src_bpos >> 1;

			VoxelBlock *src_block = src_lod.map.get_block(src_bpos);
			VoxelBlock *dst_block = dst_lod.map.get_block(dst_bpos);

			src_block->set_needs_lodding(false);

			if (dst_block == nullptr) {
				ERR_PRINT(String("Destination block {0} not found when cascading edits on LOD {1}")
								  .format(varray(dst_bpos.to_vec3(), dst_lod_index)));
				continue;
			}

			// The block and its lower LODs are expected to be available.
			// Otherwise it means the function was called too late
			CRASH_COND(src_block == nullptr);
			//CRASH_COND(dst_block == nullptr);
			CRASH_COND(src_block->voxels.is_null());
			CRASH_COND(dst_block->voxels.is_null());

			schedule_mesh_update(dst_block, dst_lod.blocks_pending_update);

			dst_block->set_modified(true);

			if (dst_lod_index != _lod_count - 1 && !dst_block->get_needs_lodding()) {
				dst_block->set_needs_lodding(true);
				dst_lod.blocks_pending_lodding.push_back(dst_bpos);
			}

			const Vector3i rel = src_bpos - (dst_bpos << 1);

			// Update lower LOD
			// This must always be done after an edit before it gets saved, otherwise LODs won't match and it will look ugly.
			// TODO Try to narrow to edited region instead of taking whole block
			{
				RWLockWrite lock(src_block->voxels->get_lock());
				src_block->voxels->downscale_to(
						**dst_block->voxels, Vector3i(), src_block->voxels->get_size(), rel * half_bs);
			}
		}

		src_lod.blocks_pending_lodding.clear();
	}

	//	uint64_t time_spent = profiling_clock.restart();
	//	if (time_spent > 10) {
	//		print_line(String("Took {0} us to update lods").format(varray(time_spent)));
	//	}
}

void VoxelLodTerrain::immerge_block(Vector3i block_pos, int lod_index) {
	VOXEL_PROFILE_SCOPE();
	ERR_FAIL_COND(lod_index >= get_lod_count());

	Lod &lod = _lods[lod_index];

	lod.map.remove_block(block_pos, BeforeUnloadAction{ _shader_material_pool, _blocks_to_save });

	lod.loading_blocks.erase(block_pos);

	// Blocks in the update queue will be cancelled in _process,
	// because it's too expensive to linear-search all blocks for each block

	// No need to remove things from blocks_pending_load,
	// This vector is filled and cleared immediately in the main process.
	// It is a member only to re-use its capacity memory over frames.
}

void VoxelLodTerrain::save_all_modified_blocks(bool with_copy) {
	flush_pending_lod_edits();

	for (int i = 0; i < _lod_count; ++i) {
		// That may cause a stutter, so should be used when the player won't notice
		_lods[i].map.for_all_blocks(ScheduleSaveAction{ _blocks_to_save });
	}

	// And flush immediately
	send_block_data_requests();
}

void VoxelLodTerrain::add_transition_update(VoxelBlock *block) {
	if (!block->pending_transition_update) {
		_blocks_pending_transition_update.push_back(block);
		block->pending_transition_update = true;
	}
}

void VoxelLodTerrain::add_transition_updates_around(Vector3i block_pos, int lod_index) {
	Lod &lod = _lods[lod_index];

	for (int dir = 0; dir < Cube::SIDE_COUNT; ++dir) {
		Vector3i npos = block_pos + Cube::g_side_normals[dir];
		VoxelBlock *nblock = lod.map.get_block(npos);

		if (nblock != nullptr) {
			add_transition_update(nblock);
		}
	}
	// TODO If a block appears at lod, neighbor blocks at lod-1 need to be updated.
	// or maybe get_transition_mask needs a different approach that also looks at higher lods?
}

void VoxelLodTerrain::process_transition_updates() {
	for (unsigned int i = 0; i < _blocks_pending_transition_update.size(); ++i) {
		VoxelBlock *block = _blocks_pending_transition_update[i];
		CRASH_COND(block == nullptr);

		if (block->is_visible()) {
			block->set_transition_mask(get_transition_mask(block->position, block->lod_index));
		}

		block->pending_transition_update = false;
	}

	_blocks_pending_transition_update.clear();
}

uint8_t VoxelLodTerrain::get_transition_mask(Vector3i block_pos, int lod_index) const {
	uint8_t transition_mask = 0;

	if (lod_index + 1 >= _lod_count) {
		return transition_mask;
	}

	const Lod &lower_lod = _lods[lod_index + 1];
	const Lod &lod = _lods[lod_index];

	const Vector3i lower_pos = block_pos >> 1;
	const Vector3i upper_pos = block_pos << 1;

	// Based on octree rules, and the fact it must have run before, check neighbor blocks of same LOD:
	// If one is missing or not visible, it means either of the following:
	// - The neighbor at lod+1 is visible or not loaded (there must be a transition)
	// - The neighbor at lod-1 is visible (no transition)

	uint8_t visible_neighbors_of_same_lod = 0;
	for (int dir = 0; dir < Cube::SIDE_COUNT; ++dir) {
		Vector3i npos = block_pos + Cube::g_side_normals[dir];

		const VoxelBlock *nblock = lod.map.get_block(npos);

		if (nblock != nullptr && nblock->is_visible()) {
			visible_neighbors_of_same_lod |= (1 << dir);
		}
	}

	if (visible_neighbors_of_same_lod != 0b111111) {
		// At least one neighbor isn't visible.
		// Check for neighbors at different LOD (there can be only one kind on a given side)
		for (int dir = 0; dir < Cube::SIDE_COUNT; ++dir) {
			int dir_mask = (1 << dir);

			if (visible_neighbors_of_same_lod & dir_mask) {
				continue;
			}

			const Vector3i side_normal = Cube::g_side_normals[dir];
			const Vector3i lower_neighbor_pos = (block_pos + side_normal) >> 1;

			if (lower_neighbor_pos != lower_pos) {
				const VoxelBlock *lower_neighbor_block = lower_lod.map.get_block(lower_neighbor_pos);

				if (lower_neighbor_block != nullptr && lower_neighbor_block->is_visible()) {
					// The block has a visible neighbor of lower LOD
					transition_mask |= dir_mask;
					continue;
				}
			}

			if (lod_index > 0) {
				// Check upper LOD neighbors.
				// There are always 4 on each side, checking any is enough

				Vector3i upper_neighbor_pos = upper_pos;
				for (unsigned int i = 0; i < Vector3i::AXIS_COUNT; ++i) {
					if (side_normal[i] == -1) {
						--upper_neighbor_pos[i];
					} else if (side_normal[i] == 1) {
						upper_neighbor_pos[i] += 2;
					}
				}

				const Lod &upper_lod = _lods[lod_index - 1];
				const VoxelBlock *upper_neighbor_block = upper_lod.map.get_block(upper_neighbor_pos);

				if (upper_neighbor_block == nullptr || upper_neighbor_block->is_visible() == false) {
					// The block has no visible neighbor yet. World border? Assume lower LOD.
					transition_mask |= dir_mask;
				}
			}
		}
	}

	return transition_mask;
}

const VoxelLodTerrain::Stats &VoxelLodTerrain::get_stats() const {
	return _stats;
}

Dictionary VoxelLodTerrain::_b_get_statistics() const {
	Dictionary d;

	// Breakdown of time spent in _process
	d["time_detect_required_blocks"] = _stats.time_detect_required_blocks;
	d["time_request_blocks_to_load"] = _stats.time_request_blocks_to_load;
	d["time_process_load_responses"] = _stats.time_process_load_responses;
	d["time_request_blocks_to_update"] = _stats.time_request_blocks_to_update;
	d["time_process_update_responses"] = _stats.time_process_update_responses;

	d["remaining_main_thread_blocks"] = _stats.remaining_main_thread_blocks;
	d["dropped_block_loads"] = _stats.dropped_block_loads;
	d["dropped_block_meshs"] = _stats.dropped_block_meshs;
	d["updated_blocks"] = _stats.updated_blocks;
	d["blocked_lods"] = _stats.blocked_lods;

	return d;
}

void VoxelLodTerrain::set_run_stream_in_editor(bool enable) {
	if (enable == _run_stream_in_editor) {
		return;
	}

	_run_stream_in_editor = enable;

	if (Engine::get_singleton()->is_editor_hint()) {
		if (_run_stream_in_editor) {
			_on_stream_params_changed();

		} else {
			// This is expected to block the main thread until the streaming thread is done.
			stop_streamer();
		}
	}
}

bool VoxelLodTerrain::is_stream_running_in_editor() const {
	return _run_stream_in_editor;
}

void VoxelLodTerrain::restart_stream() {
	_on_stream_params_changed();
}

void VoxelLodTerrain::remesh_all_blocks() {
	for (int lod_index = 0; lod_index < _lod_count; ++lod_index) {
		Lod &lod = _lods[lod_index];
		lod.map.for_all_blocks([&lod](VoxelBlock *block) {
			schedule_mesh_update(block, lod.blocks_pending_update);
		});
	}
}

void VoxelLodTerrain::set_voxel_bounds(Rect3i p_box) {
	_bounds_in_voxels =
			p_box.clipped(Rect3i::from_center_extents(Vector3i(), Vector3i(VoxelConstants::MAX_VOLUME_EXTENT)));
	// Round to octree size
	const int octree_size = get_block_size() << (get_lod_count() - 1);
	_bounds_in_voxels = _bounds_in_voxels.snapped(octree_size);
	// Can't have a smaller region than one octree
	for (unsigned i = 0; i < Vector3i::AXIS_COUNT; ++i) {
		if (_bounds_in_voxels.size[i] < octree_size) {
			_bounds_in_voxels.size[i] = octree_size;
		}
	}
}

void VoxelLodTerrain::_b_save_modified_blocks() {
	save_all_modified_blocks(true);
}

void VoxelLodTerrain::_b_set_voxel_bounds(AABB aabb) {
	// TODO Please Godot, have an integer AABB!
	set_voxel_bounds(Rect3i(aabb.position.round(), aabb.size.round()));
}

AABB VoxelLodTerrain::_b_get_voxel_bounds() const {
	const Rect3i b = get_voxel_bounds();
	return AABB(b.pos.to_vec3(), b.size.to_vec3());
}

// DEBUG LAND

Array VoxelLodTerrain::debug_raycast_block(Vector3 world_origin, Vector3 world_direction) const {
	const Transform world_to_local = get_global_transform().affine_inverse();
	Vector3 pos = world_to_local.xform(world_origin);
	const Vector3 dir = world_to_local.basis.xform(world_direction);
	const float max_distance = 256;
	const float step = 2.f;
	float distance = 0.f;

	Array hits;
	while (distance < max_distance && hits.size() == 0) {
		for (int lod_index = 0; lod_index < _lod_count; ++lod_index) {
			const Lod &lod = _lods[lod_index];
			Vector3i bpos = lod.map.voxel_to_block(Vector3i(pos)) >> lod_index;
			const VoxelBlock *block = lod.map.get_block(bpos);
			if (block != nullptr && block->is_visible() && block->has_mesh()) {
				Dictionary d;
				d["position"] = block->position.to_vec3();
				d["lod"] = block->lod_index;
				hits.append(d);
			}
		}
		distance += step;
		pos += dir * step;
	}

	return hits;
}

Dictionary VoxelLodTerrain::debug_get_block_info(Vector3 fbpos, int lod_index) const {
	Dictionary d;
	ERR_FAIL_COND_V(lod_index < 0, d);
	ERR_FAIL_COND_V(lod_index >= get_lod_count(), d);

	const Lod &lod = _lods[lod_index];
	Vector3i bpos(fbpos);

	bool meshed = false;
	bool visible = false;
	int loading_state = 0;
	const VoxelBlock *block = lod.map.get_block(bpos);

	if (block) {
		meshed = !block->has_mesh() && block->get_mesh_state() != VoxelBlock::MESH_UP_TO_DATE;
		visible = block->is_visible();
		loading_state = 2;
		d["transition_mask"] = block->get_transition_mask();
		d["recomputed_transition_mask"] = get_transition_mask(block->position, block->lod_index);

	} else if (lod.loading_blocks.has(bpos)) {
		loading_state = 1;
	}

	d["loading"] = loading_state;
	d["meshed"] = meshed;
	d["visible"] = visible;
	return d;
}

Array VoxelLodTerrain::debug_get_octrees() const {
	Array positions;
	positions.resize(_lod_octrees.size());
	int i = 0;
	for (Map<Vector3i, OctreeItem>::Element *E = _lod_octrees.front(); E; E = E->next()) {
		positions[i++] = E->key().to_vec3();
	}
	return positions;
}

#ifdef TOOLS_ENABLED

void VoxelLodTerrain::update_gizmos() {
	VOXEL_PROFILE_SCOPE();

	VoxelDebug::DebugRenderer &dr = _debug_renderer;
	dr.begin();

	const Transform parent_transform = get_global_transform();

	const int octree_size = get_block_size() << (get_lod_count() - 1);
	const Basis local_octree_basis = Basis().scaled(Vector3(octree_size, octree_size, octree_size));
	for (Map<Vector3i, OctreeItem>::Element *E = _lod_octrees.front(); E; E = E->next()) {
		const Transform local_transform(local_octree_basis, (E->key() * octree_size).to_vec3());
		dr.draw_box(parent_transform * local_transform, VoxelDebug::ID_OCTREE_BOUNDS);
	}

	const float bounds_in_voxels_len = _bounds_in_voxels.size.length();
	if (bounds_in_voxels_len < 10000) {
		const Vector3 margin = Vector3(1, 1, 1) * bounds_in_voxels_len * 0.0025f;
		const Vector3 size = _bounds_in_voxels.size.to_vec3();
		const Transform local_transform(Basis().scaled(size + margin * 2.f), _bounds_in_voxels.pos.to_vec3() - margin);
		dr.draw_box(parent_transform * local_transform, VoxelDebug::ID_VOXEL_BOUNDS);
	}

	dr.end();
}

void VoxelLodTerrain::set_show_gizmos(bool enable) {
	_show_gizmos_enabled = enable;
	if (_show_gizmos_enabled) {
		_debug_renderer.set_world(is_visible_in_tree() ? *get_world() : nullptr);
	} else {
		_debug_renderer.clear();
	}
}

#endif

Array VoxelLodTerrain::_b_debug_print_sdf_top_down(Vector3 center, Vector3 extents) const {
	Array image_array;
	image_array.resize(get_lod_count());

	for (int lod_index = 0; lod_index < get_lod_count(); ++lod_index) {
		const Rect3i world_box = Rect3i::from_center_extents(Vector3i(center) >> lod_index, Vector3i(extents) >> lod_index);

		if (world_box.size.volume() == 0) {
			continue;
		}

		Ref<VoxelBuffer> buffer_ref;
		buffer_ref.instance();
		VoxelBuffer &buffer = **buffer_ref;
		buffer.create(world_box.size);

		const Lod &lod = _lods[lod_index];

		world_box.for_each_cell([&](const Vector3i &world_pos) {
			const float v = lod.map.get_voxel_f(world_pos, VoxelBuffer::CHANNEL_SDF);
			const Vector3i rpos = world_pos - world_box.pos;
			buffer.set_voxel_f(v, rpos.x, rpos.y, rpos.z, VoxelBuffer::CHANNEL_SDF);
		});

		Ref<Image> image = buffer.debug_print_sdf_to_image_top_down();
		image_array[lod_index] = image;
	}

	return image_array;
}

int VoxelLodTerrain::_b_debug_get_block_count() const {
	int sum = 0;
	for (int lod_index = 0; lod_index < _lod_count; ++lod_index) {
		sum += _lods[lod_index].map.get_block_count();
	}
	return sum;
}

Error VoxelLodTerrain::_b_debug_dump_as_scene(String fpath) const {
	Spatial *root = memnew(Spatial);
	root->set_name(get_name());

	for (int lod_index = 0; lod_index < _lod_count; ++lod_index) {
		const Lod &lod = _lods[lod_index];

		lod.map.for_all_blocks([root](const VoxelBlock *block) {
			block->for_each_mesh_instance_with_transform([root, block](const DirectMeshInstance &dmi, Transform t) {
				Ref<Mesh> mesh = dmi.get_mesh();

				if (mesh.is_valid()) {
					MeshInstance *mi = memnew(MeshInstance);
					mi->set_mesh(mesh);
					mi->set_transform(t);
					// TODO Transition mesh visibility?
					mi->set_visible(block->is_visible());
					root->add_child(mi);
					// The owner must be set after adding to parent
					mi->set_owner(root);
				}
			});
		});
	}

	Ref<PackedScene> scene = memnew(PackedScene);
	Error err = scene->pack(root);
	if (err != OK) {
		return err;
	}
	err = ResourceSaver::save(fpath, scene, ResourceSaver::FLAG_BUNDLE_RESOURCES);

	memdelete(root);

	return err;
}

void VoxelLodTerrain::_bind_methods() {
	ClassDB::bind_method(D_METHOD("set_material", "material"), &VoxelLodTerrain::set_material);
	ClassDB::bind_method(D_METHOD("get_material"), &VoxelLodTerrain::get_material);

	ClassDB::bind_method(D_METHOD("set_view_distance", "distance_in_voxels"), &VoxelLodTerrain::set_view_distance);
	ClassDB::bind_method(D_METHOD("get_view_distance"), &VoxelLodTerrain::get_view_distance);

	ClassDB::bind_method(D_METHOD("get_generate_collisions"), &VoxelLodTerrain::get_generate_collisions);
	ClassDB::bind_method(D_METHOD("set_generate_collisions", "enabled"), &VoxelLodTerrain::set_generate_collisions);

	ClassDB::bind_method(D_METHOD("get_collision_lod_count"), &VoxelLodTerrain::get_collision_lod_count);
	ClassDB::bind_method(D_METHOD("set_collision_lod_count", "count"), &VoxelLodTerrain::set_collision_lod_count);

	ClassDB::bind_method(D_METHOD("set_lod_count", "lod_count"), &VoxelLodTerrain::set_lod_count);
	ClassDB::bind_method(D_METHOD("get_lod_count"), &VoxelLodTerrain::get_lod_count);

	ClassDB::bind_method(D_METHOD("set_lod_split_scale", "lod_split_scale"), &VoxelLodTerrain::set_lod_split_scale);
	ClassDB::bind_method(D_METHOD("get_lod_split_scale"), &VoxelLodTerrain::get_lod_split_scale);

	ClassDB::bind_method(D_METHOD("get_block_size"), &VoxelLodTerrain::get_block_size);
	ClassDB::bind_method(D_METHOD("get_block_region_extent"), &VoxelLodTerrain::get_block_region_extent);
	ClassDB::bind_method(D_METHOD("get_statistics"), &VoxelLodTerrain::_b_get_statistics);
	ClassDB::bind_method(D_METHOD("voxel_to_block_position", "lod_index"), &VoxelLodTerrain::voxel_to_block_position);

	ClassDB::bind_method(D_METHOD("get_voxel_tool"), &VoxelLodTerrain::get_voxel_tool);
	ClassDB::bind_method(D_METHOD("save_modified_blocks"), &VoxelLodTerrain::_b_save_modified_blocks);

	ClassDB::bind_method(D_METHOD("set_run_stream_in_editor"), &VoxelLodTerrain::set_run_stream_in_editor);
	ClassDB::bind_method(D_METHOD("is_stream_running_in_editor"), &VoxelLodTerrain::is_stream_running_in_editor);

	ClassDB::bind_method(D_METHOD("set_voxel_bounds"), &VoxelLodTerrain::_b_set_voxel_bounds);
	ClassDB::bind_method(D_METHOD("get_voxel_bounds"), &VoxelLodTerrain::_b_get_voxel_bounds);

	ClassDB::bind_method(D_METHOD("set_process_mode", "mode"), &VoxelLodTerrain::set_process_mode);
	ClassDB::bind_method(D_METHOD("get_process_mode"), &VoxelLodTerrain::get_process_mode);

	ClassDB::bind_method(D_METHOD("debug_raycast_block", "origin", "dir"), &VoxelLodTerrain::debug_raycast_block);
	ClassDB::bind_method(D_METHOD("debug_get_block_info", "block_pos", "lod"), &VoxelLodTerrain::debug_get_block_info);
	ClassDB::bind_method(D_METHOD("debug_get_octrees"), &VoxelLodTerrain::debug_get_octrees);
	ClassDB::bind_method(D_METHOD("debug_print_sdf_top_down", "center", "extents"),
			&VoxelLodTerrain::_b_debug_print_sdf_top_down);
	ClassDB::bind_method(D_METHOD("debug_get_block_count"), &VoxelLodTerrain::_b_debug_get_block_count);
	ClassDB::bind_method(D_METHOD("debug_dump_as_scene", "path"), &VoxelLodTerrain::_b_debug_dump_as_scene);

	//ClassDB::bind_method(D_METHOD("_on_stream_params_changed"), &VoxelLodTerrain::_on_stream_params_changed);

	BIND_ENUM_CONSTANT(PROCESS_MODE_IDLE);
	BIND_ENUM_CONSTANT(PROCESS_MODE_PHYSICS);
	BIND_ENUM_CONSTANT(PROCESS_MODE_DISABLED);

	ADD_PROPERTY(PropertyInfo(Variant::INT, "view_distance"), "set_view_distance", "get_view_distance");
	ADD_PROPERTY(PropertyInfo(Variant::INT, "lod_count"), "set_lod_count", "get_lod_count");
	ADD_PROPERTY(PropertyInfo(Variant::REAL, "lod_split_scale"), "set_lod_split_scale", "get_lod_split_scale");
	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "material", PROPERTY_HINT_RESOURCE_TYPE, "Material"),
			"set_material", "get_material");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "generate_collisions"),
			"set_generate_collisions", "get_generate_collisions");
	ADD_PROPERTY(PropertyInfo(Variant::INT, "collision_lod_count"),
			"set_collision_lod_count", "get_collision_lod_count");
	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "run_stream_in_editor"),
			"set_run_stream_in_editor", "is_stream_running_in_editor");
	ADD_PROPERTY(PropertyInfo(Variant::AABB, "voxel_bounds"), "set_voxel_bounds", "get_voxel_bounds");
}