Implement automatic LOD (Level of Detail)

-Happens on import by default for all models
-Just works (tm)
-Biasing can be later adjusted per node or per viewport (as well as globally)
-Disabled AABB.get_support test because its broken

5 files changed, 76 insertions, 10 deletions

diff --git a/editor/editor_node.cpp b/editor/editor_node.cpp
index 64b5f50b91..dfe5d64784 100644
--- a/editor/editor_node.cpp
+++ b/editor/editor_node.cpp
@@ -525,6 +525,9 @@ void EditorNode::_notification(int p_what) {
 				scene_root->set_sdf_oversize(sdf_oversize);
 				Viewport::SDFScale sdf_scale = Viewport::SDFScale(int(GLOBAL_GET("rendering/quality/2d_sdf/scale")));
 				scene_root->set_sdf_scale(sdf_scale);
+
+				float lod_threshold = GLOBAL_GET("rendering/quality/mesh_lod/threshold_pixels");
+				scene_root->set_lod_threshold(lod_threshold);
 			}
 
 			ResourceImporterTexture::get_singleton()->update_imports();
diff --git a/editor/import/resource_importer_scene.cpp b/editor/import/resource_importer_scene.cpp
index 5abae339df..d9c8bd9eb3 100644
--- a/editor/import/resource_importer_scene.cpp
+++ b/editor/import/resource_importer_scene.cpp
@@ -44,6 +44,7 @@
 #include "scene/resources/ray_shape_3d.h"
 #include "scene/resources/resource_format_text.h"
 #include "scene/resources/sphere_shape_3d.h"
+#include "scene/resources/surface_tool.h"
 #include "scene/resources/world_margin_shape_3d.h"
 
 uint32_t EditorSceneImporter::get_import_flags() const {
@@ -217,6 +218,59 @@ Ref<Material> EditorSceneImporterMesh::get_surface_material(int p_surface) const
 	return surfaces[p_surface].material;
 }
 
+void EditorSceneImporterMesh::generate_lods() {
+	if (!SurfaceTool::simplify_func) {
+		return;
+	}
+
+	for (int i = 0; i < surfaces.size(); i++) {
+		if (surfaces[i].primitive != Mesh::PRIMITIVE_TRIANGLES) {
+			continue;
+		}
+
+		surfaces.write[i].lods.clear();
+		Vector<Vector3> vertices = surfaces[i].arrays[RS::ARRAY_VERTEX];
+		Vector<int> indices = surfaces[i].arrays[RS::ARRAY_INDEX];
+		if (indices.size() == 0) {
+			continue; //no lods if no indices
+		}
+		uint32_t vertex_count = vertices.size();
+		const Vector3 *vertices_ptr = vertices.ptr();
+		AABB aabb;
+		{
+			for (uint32_t j = 0; j < vertex_count; j++) {
+				if (j == 0) {
+					aabb.position = vertices_ptr[j];
+				} else {
+					aabb.expand_to(vertices_ptr[j]);
+				}
+			}
+		}
+
+		float longest_axis_size = aabb.get_longest_axis_size();
+
+		int min_indices = 10;
+		int index_target = indices.size() / 2;
+		print_line("total: " + itos(indices.size()));
+		while (index_target > min_indices) {
+			float error;
+			Vector<int> new_indices;
+			new_indices.resize(indices.size());
+			size_t new_len = SurfaceTool::simplify_func((unsigned int *)new_indices.ptrw(), (const unsigned int *)indices.ptr(), indices.size(), (const float *)vertices_ptr, vertex_count, sizeof(Vector3), index_target, 1e20, &error);
+			print_line("shoot for " + itos(index_target) + ", got " + itos(new_len) + " distance " + rtos(error));
+			if ((int)new_len > (index_target * 120 / 100)) {
+				break; // 20 percent tolerance
+			}
+			new_indices.resize(new_len);
+			Surface::LOD lod;
+			lod.distance = error * longest_axis_size;
+			lod.indices = new_indices;
+			surfaces.write[i].lods.push_back(lod);
+			index_target /= 2;
+		}
+	}
+}
+
 bool EditorSceneImporterMesh::has_mesh() const {
 	return mesh.is_valid();
 }
@@ -1422,9 +1476,9 @@ void ResourceImporterScene::get_import_options(List<ImportOption> *r_options, in
 	r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "materials/location", PROPERTY_HINT_ENUM, "Node,Mesh"), (meshes_out || materials_out) ? 1 : 0));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "materials/storage", PROPERTY_HINT_ENUM, "Built-In,Files (.material),Files (.tres)", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_UPDATE_ALL_IF_MODIFIED), materials_out ? 1 : 0));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "materials/keep_on_reimport"), materials_out));
-	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "meshes/compress"), true));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "meshes/ensure_tangents"), true));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "meshes/storage", PROPERTY_HINT_ENUM, "Built-In,Files (.mesh),Files (.tres)"), meshes_out ? 1 : 0));
+	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "meshes/generate_lods"), true));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "meshes/light_baking", PROPERTY_HINT_ENUM, "Disabled,Enable,Gen Lightmaps", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_UPDATE_ALL_IF_MODIFIED), 0));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::FLOAT, "meshes/lightmap_texel_size", PROPERTY_HINT_RANGE, "0.001,100,0.001"), 0.1));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "skins/use_named_skins"), true));
@@ -1517,7 +1571,7 @@ Ref<Animation> ResourceImporterScene::import_animation_from_other_importer(Edito
 	return importer->import_animation(p_path, p_flags, p_bake_fps);
 }
 
-void ResourceImporterScene::_generate_meshes(Node *p_node) {
+void ResourceImporterScene::_generate_meshes(Node *p_node, bool p_generate_lods) {
 	EditorSceneImporterMeshNode *src_mesh = Object::cast_to<EditorSceneImporterMeshNode>(p_node);
 	if (src_mesh != nullptr) {
 		//is mesh
@@ -1528,6 +1582,9 @@ void ResourceImporterScene::_generate_meshes(Node *p_node) {
 
 		Ref<ArrayMesh> mesh;
 		if (!src_mesh->get_mesh()->has_mesh()) {
+			if (p_generate_lods) {
+				src_mesh->get_mesh()->generate_lods();
+			}
 			//do mesh processing
 		}
 		mesh = src_mesh->get_mesh()->get_mesh();
@@ -1542,7 +1599,7 @@ void ResourceImporterScene::_generate_meshes(Node *p_node) {
 	}
 
 	for (int i = 0; i < p_node->get_child_count(); i++) {
-		_generate_meshes(p_node->get_child(i));
+		_generate_meshes(p_node->get_child(i), p_generate_lods);
 	}
 }
 Error ResourceImporterScene::import(const String &p_source_file, const String &p_save_path, const Map<StringName, Variant> &p_options, List<String> *r_platform_variants, List<String> *r_gen_files, Variant *r_metadata) {
@@ -1583,10 +1640,6 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 		import_flags |= EditorSceneImporter::IMPORT_ANIMATION;
 	}
 
-	if (int(p_options["meshes/compress"])) {
-		import_flags |= EditorSceneImporter::IMPORT_USE_COMPRESSION;
-	}
-
 	if (bool(p_options["meshes/ensure_tangents"])) {
 		import_flags |= EditorSceneImporter::IMPORT_GENERATE_TANGENT_ARRAYS;
 	}
@@ -1641,7 +1694,9 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 		scene->set_name(p_save_path.get_file().get_basename());
 	}
 
-	_generate_meshes(scene);
+	bool gen_lods = bool(p_options["meshes/generate_lods"]);
+
+	_generate_meshes(scene, gen_lods);
 
 	err = OK;
 
diff --git a/editor/import/resource_importer_scene.h b/editor/import/resource_importer_scene.h
index 758390b367..aef6c0ac50 100644
--- a/editor/import/resource_importer_scene.h
+++ b/editor/import/resource_importer_scene.h
@@ -144,6 +144,8 @@ public:
 	float get_surface_lod_size(int p_surface, int p_lod) const;
 	Ref<Material> get_surface_material(int p_surface) const;
 
+	void generate_lods();
+
 	bool has_mesh() const;
 	Ref<ArrayMesh> get_mesh();
 	void clear();
@@ -205,7 +207,7 @@ class ResourceImporterScene : public ResourceImporter {
 	};
 
 	void _replace_owner(Node *p_node, Node *p_scene, Node *p_new_owner);
-	void _generate_meshes(Node *p_node);
+	void _generate_meshes(Node *p_node, bool p_generate_lods);
 
 public:
 	static ResourceImporterScene *get_singleton() { return singleton; }
diff --git a/editor/plugins/node_3d_editor_plugin.cpp b/editor/plugins/node_3d_editor_plugin.cpp
index ff3b50303f..f0d512e4b2 100644
--- a/editor/plugins/node_3d_editor_plugin.cpp
+++ b/editor/plugins/node_3d_editor_plugin.cpp
@@ -3017,7 +3017,8 @@ void Node3DEditorViewport::_menu_option(int p_option) {
 		case VIEW_DISPLAY_DEBUG_DECAL_ATLAS:
 		case VIEW_DISPLAY_DEBUG_SDFGI:
 		case VIEW_DISPLAY_DEBUG_SDFGI_PROBES:
-		case VIEW_DISPLAY_DEBUG_GI_BUFFER: {
+		case VIEW_DISPLAY_DEBUG_GI_BUFFER:
+		case VIEW_DISPLAY_DEBUG_DISABLE_LOD: {
 			static const int display_options[] = {
 				VIEW_DISPLAY_NORMAL,
 				VIEW_DISPLAY_WIREFRAME,
@@ -3034,6 +3035,7 @@ void Node3DEditorViewport::_menu_option(int p_option) {
 				VIEW_DISPLAY_DEBUG_SCENE_LUMINANCE,
 				VIEW_DISPLAY_DEBUG_SSAO,
 				VIEW_DISPLAY_DEBUG_GI_BUFFER,
+				VIEW_DISPLAY_DEBUG_DISABLE_LOD,
 				VIEW_DISPLAY_DEBUG_PSSM_SPLITS,
 				VIEW_DISPLAY_DEBUG_DECAL_ATLAS,
 				VIEW_DISPLAY_DEBUG_SDFGI,
@@ -3056,6 +3058,7 @@ void Node3DEditorViewport::_menu_option(int p_option) {
 				Viewport::DEBUG_DRAW_SCENE_LUMINANCE,
 				Viewport::DEBUG_DRAW_SSAO,
 				Viewport::DEBUG_DRAW_GI_BUFFER,
+				Viewport::DEBUG_DRAW_DISABLE_LOD,
 				Viewport::DEBUG_DRAW_PSSM_SPLITS,
 				Viewport::DEBUG_DRAW_DECAL_ATLAS,
 				Viewport::DEBUG_DRAW_SDFGI,
@@ -3959,6 +3962,8 @@ Node3DEditorViewport::Node3DEditorViewport(Node3DEditor *p_spatial_editor, Edito
 	display_submenu->add_radio_check_item(TTR("SSAO"), VIEW_DISPLAY_DEBUG_SSAO);
 	display_submenu->add_separator();
 	display_submenu->add_radio_check_item(TTR("GI Buffer"), VIEW_DISPLAY_DEBUG_GI_BUFFER);
+	display_submenu->add_separator();
+	display_submenu->add_radio_check_item(TTR("Disable LOD"), VIEW_DISPLAY_DEBUG_DISABLE_LOD);
 	display_submenu->set_name("display_advanced");
 	view_menu->get_popup()->add_submenu_item(TTR("Display Advanced..."), "display_advanced", VIEW_DISPLAY_ADVANCED);
 	view_menu->get_popup()->add_separator();
diff --git a/editor/plugins/node_3d_editor_plugin.h b/editor/plugins/node_3d_editor_plugin.h
index 66ee678154..079c86ceb4 100644
--- a/editor/plugins/node_3d_editor_plugin.h
+++ b/editor/plugins/node_3d_editor_plugin.h
@@ -212,6 +212,7 @@ class Node3DEditorViewport : public Control {
 		VIEW_DISPLAY_DEBUG_SDFGI,
 		VIEW_DISPLAY_DEBUG_SDFGI_PROBES,
 		VIEW_DISPLAY_DEBUG_GI_BUFFER,
+		VIEW_DISPLAY_DEBUG_DISABLE_LOD,
 		VIEW_LOCK_ROTATION,
 		VIEW_CINEMATIC_PREVIEW,
 		VIEW_AUTO_ORTHOGONAL,