Rework Mesh handling on scene importing.

-Reworked how meshes are treated by importer by using EditorSceneImporterMesh and EditorSceneImporterMeshNode. Instead of Mesh and MeshInstance, this allows more efficient processing of meshes before they are actually registered in the RenderingServer.
-Integrated MeshOptimizer
-Reworked internals of SurfaceTool to use arrays, making it more performant and easy to run optimizatons on.

7 files changed, 485 insertions, 43 deletions

diff --git a/editor/editor_node.cpp b/editor/editor_node.cpp
index 66c54c4267..8cdb865937 100644
--- a/editor/editor_node.cpp
+++ b/editor/editor_node.cpp
@@ -3654,6 +3654,9 @@ void EditorNode::register_editor_types() {
 	ClassDB::register_class<ScriptCreateDialog>();
 	ClassDB::register_class<EditorFeatureProfile>();
 	ClassDB::register_class<EditorSpinSlider>();
+	ClassDB::register_class<EditorSceneImporterMesh>();
+	ClassDB::register_class<EditorSceneImporterMeshNode>();
+
 	ClassDB::register_virtual_class<FileSystemDock>();
 
 	// FIXME: Is this stuff obsolete, or should it be ported to new APIs?
diff --git a/editor/import/editor_import_collada.cpp b/editor/import/editor_import_collada.cpp
index 270bdc3821..4e93fe6f12 100644
--- a/editor/import/editor_import_collada.cpp
+++ b/editor/import/editor_import_collada.cpp
@@ -67,7 +67,7 @@ struct ColladaImport {
 
 	Map<String, NodeMap> node_map; //map from collada node to engine node
 	Map<String, String> node_name_map; //map from collada node to engine node
-	Map<String, Ref<ArrayMesh>> mesh_cache;
+	Map<String, Ref<EditorSceneImporterMesh>> mesh_cache;
 	Map<String, Ref<Curve3D>> curve_cache;
 	Map<String, Ref<Material>> material_cache;
 	Map<Collada::Node *, Skeleton3D *> skeleton_map;
@@ -83,7 +83,7 @@ struct ColladaImport {
 	Error _create_scene(Collada::Node *p_node, Node3D *p_parent);
 	Error _create_resources(Collada::Node *p_node, bool p_use_compression);
 	Error _create_material(const String &p_target);
-	Error _create_mesh_surfaces(bool p_optimize, Ref<ArrayMesh> &p_mesh, const Map<String, Collada::NodeGeometry::Material> &p_material_map, const Collada::MeshData &meshdata, const Transform &p_local_xform, const Vector<int> &bone_remap, const Collada::SkinControllerData *p_skin_controller, const Collada::MorphControllerData *p_morph_data, Vector<Ref<ArrayMesh>> p_morph_meshes = Vector<Ref<ArrayMesh>>(), bool p_use_compression = false, bool p_use_mesh_material = false);
+	Error _create_mesh_surfaces(bool p_optimize, Ref<EditorSceneImporterMesh> &p_mesh, const Map<String, Collada::NodeGeometry::Material> &p_material_map, const Collada::MeshData &meshdata, const Transform &p_local_xform, const Vector<int> &bone_remap, const Collada::SkinControllerData *p_skin_controller, const Collada::MorphControllerData *p_morph_data, Vector<Ref<EditorSceneImporterMesh>> p_morph_meshes = Vector<Ref<EditorSceneImporterMesh>>(), bool p_use_compression = false, bool p_use_mesh_material = false);
 	Error load(const String &p_path, int p_flags, bool p_force_make_tangents = false, bool p_use_compression = false);
 	void _fix_param_animation_tracks();
 	void create_animation(int p_clip, bool p_make_tracks_in_all_bones, bool p_import_value_tracks);
@@ -278,8 +278,8 @@ Error ColladaImport::_create_scene(Collada::Node *p_node, Node3D *p_parent) {
 				node = memnew(Path3D);
 			} else {
 				//mesh since nothing else
-				node = memnew(MeshInstance3D);
-				//Object::cast_to<MeshInstance3D>(node)->set_flag(GeometryInstance3D::FLAG_USE_BAKED_LIGHT, true);
+				node = memnew(EditorSceneImporterMeshNode);
+				//Object::cast_to<EditorSceneImporterMeshNode>(node)->set_flag(GeometryInstance3D::FLAG_USE_BAKED_LIGHT, true);
 			}
 		} break;
 		case Collada::Node::TYPE_SKELETON: {
@@ -440,7 +440,7 @@ Error ColladaImport::_create_material(const String &p_target) {
 	return OK;
 }
 
-Error ColladaImport::_create_mesh_surfaces(bool p_optimize, Ref<ArrayMesh> &p_mesh, const Map<String, Collada::NodeGeometry::Material> &p_material_map, const Collada::MeshData &meshdata, const Transform &p_local_xform, const Vector<int> &bone_remap, const Collada::SkinControllerData *p_skin_controller, const Collada::MorphControllerData *p_morph_data, Vector<Ref<ArrayMesh>> p_morph_meshes, bool p_use_compression, bool p_use_mesh_material) {
+Error ColladaImport::_create_mesh_surfaces(bool p_optimize, Ref<EditorSceneImporterMesh> &p_mesh, const Map<String, Collada::NodeGeometry::Material> &p_material_map, const Collada::MeshData &meshdata, const Transform &p_local_xform, const Vector<int> &bone_remap, const Collada::SkinControllerData *p_skin_controller, const Collada::MorphControllerData *p_morph_data, Vector<Ref<EditorSceneImporterMesh>> p_morph_meshes, bool p_use_compression, bool p_use_mesh_material) {
 	bool local_xform_mirror = p_local_xform.basis.determinant() < 0;
 
 	if (p_morph_data) {
@@ -457,9 +457,9 @@ Error ColladaImport::_create_mesh_surfaces(bool p_optimize, Ref<ArrayMesh> &p_me
 			p_mesh->add_blend_shape(name);
 		}
 		if (p_morph_data->mode == "RELATIVE") {
-			p_mesh->set_blend_shape_mode(ArrayMesh::BLEND_SHAPE_MODE_RELATIVE);
+			p_mesh->set_blend_shape_mode(Mesh::BLEND_SHAPE_MODE_RELATIVE);
 		} else if (p_morph_data->mode == "NORMALIZED") {
-			p_mesh->set_blend_shape_mode(ArrayMesh::BLEND_SHAPE_MODE_NORMALIZED);
+			p_mesh->set_blend_shape_mode(Mesh::BLEND_SHAPE_MODE_NORMALIZED);
 		}
 	}
 
@@ -897,7 +897,7 @@ Error ColladaImport::_create_mesh_surfaces(bool p_optimize, Ref<ArrayMesh> &p_me
 			////////////////////////////
 
 			for (int mi = 0; mi < p_morph_meshes.size(); mi++) {
-				Array a = p_morph_meshes[mi]->surface_get_arrays(surface);
+				Array a = p_morph_meshes[mi]->get_surface_arrays(surface);
 				//add valid weight and bone arrays if they exist, TODO check if they are unique to shape (generally not)
 
 				if (has_weights) {
@@ -910,14 +910,15 @@ Error ColladaImport::_create_mesh_surfaces(bool p_optimize, Ref<ArrayMesh> &p_me
 				mr.push_back(a);
 			}
 
-			p_mesh->add_surface_from_arrays(Mesh::PRIMITIVE_TRIANGLES, d, mr, Dictionary(), 0);
-
+			String surface_name;
+			Ref<Material> mat;
 			if (material.is_valid()) {
 				if (p_use_mesh_material) {
-					p_mesh->surface_set_material(surface, material);
+					mat = material;
 				}
-				p_mesh->surface_set_name(surface, material->get_name());
+				surface_name = material->get_name();
 			}
+			p_mesh->add_surface(Mesh::PRIMITIVE_TRIANGLES, d, mr, Dictionary(), mat, surface_name);
 		}
 
 		/*****************/
@@ -1002,10 +1003,10 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 			}
 		}
 
-		if (Object::cast_to<MeshInstance3D>(node)) {
+		if (Object::cast_to<EditorSceneImporterMeshNode>(node)) {
 			Collada::NodeGeometry *ng2 = static_cast<Collada::NodeGeometry *>(p_node);
 
-			MeshInstance3D *mi = Object::cast_to<MeshInstance3D>(node);
+			EditorSceneImporterMeshNode *mi = Object::cast_to<EditorSceneImporterMeshNode>(node);
 
 			ERR_FAIL_COND_V(!mi, ERR_BUG);
 
@@ -1014,7 +1015,7 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 			String meshid;
 			Transform apply_xform;
 			Vector<int> bone_remap;
-			Vector<Ref<ArrayMesh>> morphs;
+			Vector<Ref<EditorSceneImporterMesh>> morphs;
 
 			if (ng2->controller) {
 				String ngsource = ng2->source;
@@ -1083,10 +1084,10 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 							for (int i = 0; i < names.size(); i++) {
 								String meshid2 = names[i];
 								if (collada.state.mesh_data_map.has(meshid2)) {
-									Ref<ArrayMesh> mesh = Ref<ArrayMesh>(memnew(ArrayMesh));
+									Ref<EditorSceneImporterMesh> mesh = Ref<EditorSceneImporterMesh>(memnew(EditorSceneImporterMesh));
 									const Collada::MeshData &meshdata = collada.state.mesh_data_map[meshid2];
 									mesh->set_name(meshdata.name);
-									Error err = _create_mesh_surfaces(false, mesh, ng2->material_map, meshdata, apply_xform, bone_remap, skin, nullptr, Vector<Ref<ArrayMesh>>(), false);
+									Error err = _create_mesh_surfaces(false, mesh, ng2->material_map, meshdata, apply_xform, bone_remap, skin, nullptr, Vector<Ref<EditorSceneImporterMesh>>(), false);
 									ERR_FAIL_COND_V(err, err);
 
 									morphs.push_back(mesh);
@@ -1109,7 +1110,7 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 				meshid = ng2->source;
 			}
 
-			Ref<ArrayMesh> mesh;
+			Ref<EditorSceneImporterMesh> mesh;
 			if (mesh_cache.has(meshid)) {
 				mesh = mesh_cache[meshid];
 			} else {
@@ -1117,7 +1118,7 @@ Error ColladaImport::_create_resources(Collada::Node *p_node, bool p_use_compres
 					//bleh, must ignore invalid
 
 					ERR_FAIL_COND_V(!collada.state.mesh_data_map.has(meshid), ERR_INVALID_DATA);
-					mesh = Ref<ArrayMesh>(memnew(ArrayMesh));
+					mesh = Ref<EditorSceneImporterMesh>(memnew(EditorSceneImporterMesh));
 					const Collada::MeshData &meshdata = collada.state.mesh_data_map[meshid];
 					mesh->set_name(meshdata.name);
 					Error err = _create_mesh_surfaces(morphs.size() == 0, mesh, ng2->material_map, meshdata, apply_xform, bone_remap, skin, morph, morphs, p_use_compression, use_mesh_builtin_materials);
diff --git a/editor/import/editor_scene_importer_gltf.cpp b/editor/import/editor_scene_importer_gltf.cpp
index ac76f67ef9..1059692ca0 100644
--- a/editor/import/editor_scene_importer_gltf.cpp
+++ b/editor/import/editor_scene_importer_gltf.cpp
@@ -970,8 +970,6 @@ Error EditorSceneImporterGLTF::_parse_meshes(GLTFState &state) {
 		return OK;
 	}
 
-	uint32_t mesh_flags = 0;
-
 	Array meshes = state.json["meshes"];
 	for (GLTFMeshIndex i = 0; i < meshes.size(); i++) {
 		print_verbose("glTF: Parsing mesh: " + itos(i));
@@ -979,6 +977,7 @@ Error EditorSceneImporterGLTF::_parse_meshes(GLTFState &state) {
 
 		GLTFMesh mesh;
 		mesh.mesh.instance();
+		bool has_vertex_color = false;
 
 		ERR_FAIL_COND_V(!d.has("primitives"), ERR_PARSE_ERROR);
 
@@ -1034,6 +1033,7 @@ Error EditorSceneImporterGLTF::_parse_meshes(GLTFState &state) {
 			}
 			if (a.has("COLOR_0")) {
 				array[Mesh::ARRAY_COLOR] = _decode_accessor_as_color(state, a["COLOR_0"], true);
+				has_vertex_color = true;
 			}
 			if (a.has("JOINTS_0")) {
 				array[Mesh::ARRAY_BONES] = _decode_accessor_as_ints(state, a["JOINTS_0"], true);
@@ -1112,7 +1112,7 @@ Error EditorSceneImporterGLTF::_parse_meshes(GLTFState &state) {
 
 				//ideally BLEND_SHAPE_MODE_RELATIVE since gltf2 stores in displacement
 				//but it could require a larger refactor?
-				mesh.mesh->set_blend_shape_mode(ArrayMesh::BLEND_SHAPE_MODE_NORMALIZED);
+				mesh.mesh->set_blend_shape_mode(Mesh::BLEND_SHAPE_MODE_NORMALIZED);
 
 				if (j == 0) {
 					const Array &target_names = extras.has("targetNames") ? (Array)extras["targetNames"] : Array();
@@ -1226,21 +1226,25 @@ Error EditorSceneImporterGLTF::_parse_meshes(GLTFState &state) {
 			}
 
 			//just add it
-			mesh.mesh->add_surface_from_arrays(primitive, array, morphs, Dictionary(), mesh_flags);
 
+			Ref<Material> mat;
 			if (p.has("material")) {
 				const int material = p["material"];
 				ERR_FAIL_INDEX_V(material, state.materials.size(), ERR_FILE_CORRUPT);
-				const Ref<Material> &mat = state.materials[material];
-
-				mesh.mesh->surface_set_material(mesh.mesh->get_surface_count() - 1, mat);
-			} else {
-				Ref<StandardMaterial3D> mat;
-				mat.instance();
-				mat->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
+				Ref<StandardMaterial3D> mat3d = state.materials[material];
+				if (has_vertex_color) {
+					mat3d->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
+				}
+				mat = mat3d;
 
-				mesh.mesh->surface_set_material(mesh.mesh->get_surface_count() - 1, mat);
+			} else if (has_vertex_color) {
+				Ref<StandardMaterial3D> mat3d;
+				mat3d.instance();
+				mat3d->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
+				mat = mat3d;
 			}
+
+			mesh.mesh->add_surface(primitive, array, morphs, Dictionary(), mat);
 		}
 
 		mesh.blend_weights.resize(mesh.mesh->get_blend_shape_count());
@@ -1440,7 +1444,8 @@ Error EditorSceneImporterGLTF::_parse_materials(GLTFState &state) {
 		if (d.has("name")) {
 			material->set_name(d["name"]);
 		}
-		material->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
+		//don't do this here only if vertex color exists
+		//material->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
 
 		if (d.has("pbrMetallicRoughness")) {
 			const Dictionary &mr = d["pbrMetallicRoughness"];
@@ -2586,12 +2591,12 @@ BoneAttachment3D *EditorSceneImporterGLTF::_generate_bone_attachment(GLTFState &
 	return bone_attachment;
 }
 
-MeshInstance3D *EditorSceneImporterGLTF::_generate_mesh_instance(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index) {
+EditorSceneImporterMeshNode *EditorSceneImporterGLTF::_generate_mesh_instance(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index) {
 	const GLTFNode *gltf_node = state.nodes[node_index];
 
 	ERR_FAIL_INDEX_V(gltf_node->mesh, state.meshes.size(), nullptr);
 
-	MeshInstance3D *mi = memnew(MeshInstance3D);
+	EditorSceneImporterMeshNode *mi = memnew(EditorSceneImporterMeshNode);
 	print_verbose("glTF: Creating mesh for: " + gltf_node->name);
 
 	GLTFMesh &mesh = state.meshes.write[gltf_node->mesh];
@@ -3058,7 +3063,7 @@ void EditorSceneImporterGLTF::_process_mesh_instances(GLTFState &state, Node3D *
 			const GLTFSkinIndex skin_i = node->skin;
 
 			Map<GLTFNodeIndex, Node *>::Element *mi_element = state.scene_nodes.find(node_i);
-			MeshInstance3D *mi = Object::cast_to<MeshInstance3D>(mi_element->get());
+			EditorSceneImporterMeshNode *mi = Object::cast_to<EditorSceneImporterMeshNode>(mi_element->get());
 			ERR_FAIL_COND(mi == nullptr);
 
 			const GLTFSkeletonIndex skel_i = state.skins[node->skin].skeleton;
diff --git a/editor/import/editor_scene_importer_gltf.h b/editor/import/editor_scene_importer_gltf.h
index 5ea8bf17b8..6390f46524 100644
--- a/editor/import/editor_scene_importer_gltf.h
+++ b/editor/import/editor_scene_importer_gltf.h
@@ -38,7 +38,7 @@
 
 class AnimationPlayer;
 class BoneAttachment3D;
-class MeshInstance3D;
+class EditorSceneImporterMeshNode;
 
 class EditorSceneImporterGLTF : public EditorSceneImporter {
 	GDCLASS(EditorSceneImporterGLTF, EditorSceneImporter);
@@ -199,7 +199,7 @@ class EditorSceneImporterGLTF : public EditorSceneImporter {
 	};
 
 	struct GLTFMesh {
-		Ref<ArrayMesh> mesh;
+		Ref<EditorSceneImporterMesh> mesh;
 		Vector<float> blend_weights;
 	};
 
@@ -262,7 +262,7 @@ class EditorSceneImporterGLTF : public EditorSceneImporter {
 		Vector<GLTFAccessor> accessors;
 
 		Vector<GLTFMesh> meshes; //meshes are loaded directly, no reason not to.
-		Vector<Ref<Material>> materials;
+		Vector<Ref<StandardMaterial3D>> materials;
 
 		String scene_name;
 		Vector<int> root_nodes;
@@ -355,7 +355,7 @@ class EditorSceneImporterGLTF : public EditorSceneImporter {
 	Error _parse_animations(GLTFState &state);
 
 	BoneAttachment3D *_generate_bone_attachment(GLTFState &state, Skeleton3D *skeleton, const GLTFNodeIndex node_index);
-	MeshInstance3D *_generate_mesh_instance(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index);
+	EditorSceneImporterMeshNode *_generate_mesh_instance(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index);
 	Camera3D *_generate_camera(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index);
 	Light3D *_generate_light(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index);
 	Node3D *_generate_spatial(GLTFState &state, Node *scene_parent, const GLTFNodeIndex node_index);
diff --git a/editor/import/resource_importer_obj.cpp b/editor/import/resource_importer_obj.cpp
index d4560a2984..30c7b2920a 100644
--- a/editor/import/resource_importer_obj.cpp
+++ b/editor/import/resource_importer_obj.cpp
@@ -225,6 +225,8 @@ static Error _parse_obj(const String &p_path, List<Ref<Mesh>> &r_meshes, bool p_
 	String current_material_library;
 	String current_material;
 	String current_group;
+	uint32_t smooth_group = 0;
+	bool smoothing = true;
 
 	while (true) {
 		String l = f->get_line().strip_edges();
@@ -315,6 +317,10 @@ static Error _parse_obj(const String &p_path, List<Ref<Mesh>> &r_meshes, bool p_
 					Vector3 vertex = vertices[vtx];
 					//if (weld_vertices)
 					//	vertex.snap(Vector3(weld_tolerance, weld_tolerance, weld_tolerance));
+					if (!smoothing) {
+						smooth_group++;
+					}
+					surf_tool->set_smooth_group(smooth_group);
 					surf_tool->add_vertex(vertex);
 				}
 
@@ -322,10 +328,15 @@ static Error _parse_obj(const String &p_path, List<Ref<Mesh>> &r_meshes, bool p_
 			}
 		} else if (l.begins_with("s ")) { //smoothing
 			String what = l.substr(2, l.length()).strip_edges();
+			bool do_smooth;
 			if (what == "off") {
-				surf_tool->add_smooth_group(false);
+				do_smooth = false;
 			} else {
-				surf_tool->add_smooth_group(true);
+				do_smooth = true;
+			}
+			if (do_smooth != smoothing) {
+				smooth_group++;
+				smoothing = do_smooth;
 			}
 		} else if (/*l.begins_with("g ") ||*/ l.begins_with("usemtl ") || (l.begins_with("o ") || f->eof_reached())) { //commit group to mesh
 			//groups are too annoying
@@ -426,8 +437,15 @@ Node *EditorOBJImporter::import_scene(const String &p_path, uint32_t p_flags, in
 	Node3D *scene = memnew(Node3D);
 
 	for (List<Ref<Mesh>>::Element *E = meshes.front(); E; E = E->next()) {
-		MeshInstance3D *mi = memnew(MeshInstance3D);
-		mi->set_mesh(E->get());
+		Ref<EditorSceneImporterMesh> mesh;
+		mesh.instance();
+		Ref<Mesh> m = E->get();
+		for (int i = 0; i < m->get_surface_count(); i++) {
+			mesh->add_surface(m->surface_get_primitive_type(i), m->surface_get_arrays(i), Array(), Dictionary(), m->surface_get_material(i));
+		}
+
+		EditorSceneImporterMeshNode *mi = memnew(EditorSceneImporterMeshNode);
+		mi->set_mesh(mesh);
 		mi->set_name(E->get()->get_name());
 		scene->add_child(mi);
 		mi->set_owner(scene);
diff --git a/editor/import/resource_importer_scene.cpp b/editor/import/resource_importer_scene.cpp
index fc4f673ec4..5abae339df 100644
--- a/editor/import/resource_importer_scene.cpp
+++ b/editor/import/resource_importer_scene.cpp
@@ -119,6 +119,304 @@ void EditorSceneImporter::_bind_methods() {
 	BIND_CONSTANT(IMPORT_USE_COMPRESSION);
 }
 
+////////////////////////////////////////////////
+
+void EditorSceneImporterMesh::add_blend_shape(const String &p_name) {
+	ERR_FAIL_COND(surfaces.size() > 0);
+	blend_shapes.push_back(p_name);
+}
+
+int EditorSceneImporterMesh::get_blend_shape_count() const {
+	return blend_shapes.size();
+}
+
+String EditorSceneImporterMesh::get_blend_shape_name(int p_blend_shape) const {
+	ERR_FAIL_INDEX_V(p_blend_shape, blend_shapes.size(), String());
+	return blend_shapes[p_blend_shape];
+}
+
+void EditorSceneImporterMesh::set_blend_shape_mode(Mesh::BlendShapeMode p_blend_shape_mode) {
+	blend_shape_mode = p_blend_shape_mode;
+}
+Mesh::BlendShapeMode EditorSceneImporterMesh::get_blend_shape_mode() const {
+	return blend_shape_mode;
+}
+
+void EditorSceneImporterMesh::add_surface(Mesh::PrimitiveType p_primitive, const Array &p_arrays, const Array &p_blend_shapes, const Dictionary &p_lods, const Ref<Material> &p_material, const String &p_name) {
+	ERR_FAIL_COND(p_blend_shapes.size() != blend_shapes.size());
+	ERR_FAIL_COND(p_arrays.size() != Mesh::ARRAY_MAX);
+	Surface s;
+	s.primitive = p_primitive;
+	s.arrays = p_arrays;
+	s.name = p_name;
+
+	for (int i = 0; i < blend_shapes.size(); i++) {
+		Array bsdata = p_blend_shapes[i];
+		ERR_FAIL_COND(bsdata.size() != Mesh::ARRAY_MAX);
+		Surface::BlendShape bs;
+		bs.arrays = bsdata;
+		s.blend_shape_data.push_back(bs);
+	}
+
+	List<Variant> lods;
+	p_lods.get_key_list(&lods);
+	for (List<Variant>::Element *E = lods.front(); E; E = E->next()) {
+		ERR_CONTINUE(!E->get().is_num());
+		Surface::LOD lod;
+		lod.distance = E->get();
+		lod.indices = p_lods[E->get()];
+		ERR_CONTINUE(lod.indices.size() == 0);
+		s.lods.push_back(lod);
+	}
+
+	s.material = p_material;
+
+	surfaces.push_back(s);
+	mesh.unref();
+}
+int EditorSceneImporterMesh::get_surface_count() const {
+	return surfaces.size();
+}
+
+Mesh::PrimitiveType EditorSceneImporterMesh::get_surface_primitive_type(int p_surface) {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), Mesh::PRIMITIVE_MAX);
+	return surfaces[p_surface].primitive;
+}
+Array EditorSceneImporterMesh::get_surface_arrays(int p_surface) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), Array());
+	return surfaces[p_surface].arrays;
+}
+String EditorSceneImporterMesh::get_surface_name(int p_surface) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), String());
+	return surfaces[p_surface].name;
+}
+Array EditorSceneImporterMesh::get_surface_blend_shape_arrays(int p_surface, int p_blend_shape) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), Array());
+	ERR_FAIL_INDEX_V(p_blend_shape, surfaces[p_surface].blend_shape_data.size(), Array());
+	return surfaces[p_surface].blend_shape_data[p_blend_shape].arrays;
+}
+int EditorSceneImporterMesh::get_surface_lod_count(int p_surface) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), 0);
+	return surfaces[p_surface].lods.size();
+}
+Vector<int> EditorSceneImporterMesh::get_surface_lod_indices(int p_surface, int p_lod) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), Vector<int>());
+	ERR_FAIL_INDEX_V(p_lod, surfaces[p_surface].lods.size(), Vector<int>());
+
+	return surfaces[p_surface].lods[p_lod].indices;
+}
+
+float EditorSceneImporterMesh::get_surface_lod_size(int p_surface, int p_lod) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), 0);
+	ERR_FAIL_INDEX_V(p_lod, surfaces[p_surface].lods.size(), 0);
+	return surfaces[p_surface].lods[p_lod].distance;
+}
+
+Ref<Material> EditorSceneImporterMesh::get_surface_material(int p_surface) const {
+	ERR_FAIL_INDEX_V(p_surface, surfaces.size(), Ref<Material>());
+	return surfaces[p_surface].material;
+}
+
+bool EditorSceneImporterMesh::has_mesh() const {
+	return mesh.is_valid();
+}
+
+Ref<ArrayMesh> EditorSceneImporterMesh::get_mesh() {
+	ERR_FAIL_COND_V(surfaces.size() == 0, Ref<ArrayMesh>());
+
+	if (mesh.is_null()) {
+		mesh.instance();
+		for (int i = 0; i < blend_shapes.size(); i++) {
+			mesh->add_blend_shape(blend_shapes[i]);
+		}
+		mesh->set_blend_shape_mode(blend_shape_mode);
+		for (int i = 0; i < surfaces.size(); i++) {
+			Array bs_data;
+			if (surfaces[i].blend_shape_data.size()) {
+				for (int j = 0; j < surfaces[i].blend_shape_data.size(); j++) {
+					bs_data.push_back(surfaces[i].blend_shape_data[j].arrays);
+				}
+			}
+			Dictionary lods;
+			if (surfaces[i].lods.size()) {
+				for (int j = 0; j < surfaces[i].lods.size(); j++) {
+					lods[surfaces[i].lods[j].distance] = surfaces[i].lods[j].indices;
+				}
+			}
+
+			mesh->add_surface_from_arrays(surfaces[i].primitive, surfaces[i].arrays, bs_data, lods);
+			if (surfaces[i].material.is_valid()) {
+				mesh->surface_set_material(mesh->get_surface_count() - 1, surfaces[i].material);
+			}
+			if (surfaces[i].name != String()) {
+				mesh->surface_set_name(mesh->get_surface_count() - 1, surfaces[i].name);
+			}
+		}
+	}
+
+	return mesh;
+}
+
+void EditorSceneImporterMesh::clear() {
+	surfaces.clear();
+	blend_shapes.clear();
+	mesh.unref();
+}
+
+void EditorSceneImporterMesh::_set_data(const Dictionary &p_data) {
+	clear();
+	if (p_data.has("blend_shape_names")) {
+		blend_shapes = p_data["blend_shape_names"];
+	}
+	if (p_data.has("surfaces")) {
+		Array surface_arr = p_data["surfaces"];
+		for (int i = 0; i < surface_arr.size(); i++) {
+			Dictionary s = surface_arr[i];
+			ERR_CONTINUE(!s.has("primitive"));
+			ERR_CONTINUE(!s.has("arrays"));
+			Mesh::PrimitiveType prim = Mesh::PrimitiveType(int(s["primitive"]));
+			ERR_CONTINUE(prim >= Mesh::PRIMITIVE_MAX);
+			Array arr = s["arrays"];
+			Dictionary lods;
+			String name;
+			if (s.has("name")) {
+				name = s["name"];
+			}
+			if (s.has("lods")) {
+				lods = s["lods"];
+			}
+			Array blend_shapes;
+			if (s.has("blend_shapes")) {
+				blend_shapes = s["blend_shapes"];
+			}
+			Ref<Material> material;
+			if (s.has("material")) {
+				material = s["material"];
+			}
+			add_surface(prim, arr, blend_shapes, lods, material, name);
+		}
+	}
+}
+Dictionary EditorSceneImporterMesh::_get_data() const {
+	Dictionary data;
+	if (blend_shapes.size()) {
+		data["blend_shape_names"] = blend_shapes;
+	}
+	Array surface_arr;
+	for (int i = 0; i < surfaces.size(); i++) {
+		Dictionary d;
+		d["primitive"] = surfaces[i].primitive;
+		d["arrays"] = surfaces[i].arrays;
+		if (surfaces[i].blend_shape_data.size()) {
+			Array bs_data;
+			for (int j = 0; j < surfaces[i].blend_shape_data.size(); j++) {
+				bs_data.push_back(surfaces[i].blend_shape_data[j].arrays);
+			}
+			d["blend_shapes"] = bs_data;
+		}
+		if (surfaces[i].lods.size()) {
+			Dictionary lods;
+			for (int j = 0; j < surfaces[i].lods.size(); j++) {
+				lods[surfaces[i].lods[j].distance] = surfaces[i].lods[j].indices;
+			}
+			d["lods"] = lods;
+		}
+
+		if (surfaces[i].material.is_valid()) {
+			d["material"] = surfaces[i].material;
+		}
+
+		if (surfaces[i].name != String()) {
+			d["name"] = surfaces[i].name;
+		}
+
+		surface_arr.push_back(d);
+	}
+	data["surfaces"] = surface_arr;
+	return data;
+}
+
+void EditorSceneImporterMesh::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("add_blend_shape", "name"), &EditorSceneImporterMesh::add_blend_shape);
+	ClassDB::bind_method(D_METHOD("get_blend_shape_count"), &EditorSceneImporterMesh::get_blend_shape_count);
+	ClassDB::bind_method(D_METHOD("get_blend_shape_name", "blend_shape_idx"), &EditorSceneImporterMesh::get_blend_shape_name);
+
+	ClassDB::bind_method(D_METHOD("set_blend_shape_mode", "mode"), &EditorSceneImporterMesh::set_blend_shape_mode);
+	ClassDB::bind_method(D_METHOD("get_blend_shape_mode"), &EditorSceneImporterMesh::get_blend_shape_mode);
+
+	ClassDB::bind_method(D_METHOD("add_surface", "primitive", "arrays", "blend_shapes", "lods", "material"), &EditorSceneImporterMesh::add_surface, DEFVAL(Array()), DEFVAL(Dictionary()), DEFVAL(Ref<Material>()), DEFVAL(String()));
+
+	ClassDB::bind_method(D_METHOD("get_surface_count"), &EditorSceneImporterMesh::get_surface_count);
+	ClassDB::bind_method(D_METHOD("get_surface_primitive_type", "surface_idx"), &EditorSceneImporterMesh::get_surface_primitive_type);
+	ClassDB::bind_method(D_METHOD("get_surface_name", "surface_idx"), &EditorSceneImporterMesh::get_surface_name);
+	ClassDB::bind_method(D_METHOD("get_surface_arrays", "surface_idx"), &EditorSceneImporterMesh::get_surface_arrays);
+	ClassDB::bind_method(D_METHOD("get_surface_blend_shape_arrays", "surface_idx", "blend_shape_idx"), &EditorSceneImporterMesh::get_surface_blend_shape_arrays);
+	ClassDB::bind_method(D_METHOD("get_surface_lod_count", "surface_idx"), &EditorSceneImporterMesh::get_surface_lod_count);
+	ClassDB::bind_method(D_METHOD("get_surface_lod_size", "surface_idx", "lod_idx"), &EditorSceneImporterMesh::get_surface_lod_size);
+	ClassDB::bind_method(D_METHOD("get_surface_lod_indices", "surface_idx", "lod_idx"), &EditorSceneImporterMesh::get_surface_lod_indices);
+	ClassDB::bind_method(D_METHOD("get_surface_material", "surface_idx"), &EditorSceneImporterMesh::get_surface_material);
+
+	ClassDB::bind_method(D_METHOD("get_mesh"), &EditorSceneImporterMesh::get_mesh);
+	ClassDB::bind_method(D_METHOD("clear"), &EditorSceneImporterMesh::clear);
+
+	ClassDB::bind_method(D_METHOD("_set_data", "data"), &EditorSceneImporterMesh::_set_data);
+	ClassDB::bind_method(D_METHOD("_get_data"), &EditorSceneImporterMesh::_get_data);
+
+	ADD_PROPERTY(PropertyInfo(Variant::DICTIONARY, "_data", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NOEDITOR), "_set_data", "_get_data");
+}
+
+void EditorSceneImporterMeshNode::set_mesh(const Ref<EditorSceneImporterMesh> &p_mesh) {
+	mesh = p_mesh;
+}
+Ref<EditorSceneImporterMesh> EditorSceneImporterMeshNode::get_mesh() const {
+	return mesh;
+}
+
+void EditorSceneImporterMeshNode::set_skin(const Ref<Skin> &p_skin) {
+	skin = p_skin;
+}
+Ref<Skin> EditorSceneImporterMeshNode::get_skin() const {
+	return skin;
+}
+
+void EditorSceneImporterMeshNode::set_surface_material(int p_idx, const Ref<Material> &p_material) {
+	ERR_FAIL_COND(p_idx < 0);
+	if (p_idx >= surface_materials.size()) {
+		surface_materials.resize(p_idx + 1);
+	}
+
+	surface_materials.write[p_idx] = p_material;
+}
+Ref<Material> EditorSceneImporterMeshNode::get_surface_material(int p_idx) const {
+	ERR_FAIL_COND_V(p_idx < 0, Ref<Material>());
+	if (p_idx >= surface_materials.size()) {
+		return Ref<Material>();
+	}
+	return surface_materials[p_idx];
+}
+
+void EditorSceneImporterMeshNode::set_skeleton_path(const NodePath &p_path) {
+	skeleton_path = p_path;
+}
+NodePath EditorSceneImporterMeshNode::get_skeleton_path() const {
+	return skeleton_path;
+}
+
+void EditorSceneImporterMeshNode::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("set_mesh", "mesh"), &EditorSceneImporterMeshNode::set_mesh);
+	ClassDB::bind_method(D_METHOD("get_mesh"), &EditorSceneImporterMeshNode::get_mesh);
+
+	ClassDB::bind_method(D_METHOD("set_skin", "skin"), &EditorSceneImporterMeshNode::set_skin);
+	ClassDB::bind_method(D_METHOD("get_skin"), &EditorSceneImporterMeshNode::get_skin);
+
+	ClassDB::bind_method(D_METHOD("set_skeleton_path", "skeleton_path"), &EditorSceneImporterMeshNode::set_skeleton_path);
+	ClassDB::bind_method(D_METHOD("get_skeleton_path"), &EditorSceneImporterMeshNode::get_skeleton_path);
+
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "mesh", PROPERTY_HINT_RESOURCE_TYPE, "EditorSceneImporterMesh"), "set_mesh", "get_mesh");
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "skin", PROPERTY_HINT_RESOURCE_TYPE, "Skin"), "set_skin", "get_skin");
+	ADD_PROPERTY(PropertyInfo(Variant::NODE_PATH, "skeleton_path", PROPERTY_HINT_NODE_PATH_VALID_TYPES, "Skeleton"), "set_skeleton_path", "get_skeleton_path");
+}
+
 /////////////////////////////////
 void EditorScenePostImport::_bind_methods() {
 	BIND_VMETHOD(MethodInfo(Variant::OBJECT, "post_import", PropertyInfo(Variant::OBJECT, "scene")));
@@ -1219,6 +1517,34 @@ 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) {
+	EditorSceneImporterMeshNode *src_mesh = Object::cast_to<EditorSceneImporterMeshNode>(p_node);
+	if (src_mesh != nullptr) {
+		//is mesh
+		MeshInstance3D *mesh_node = memnew(MeshInstance3D);
+		mesh_node->set_transform(src_mesh->get_transform());
+		mesh_node->set_skin(src_mesh->get_skin());
+		mesh_node->set_skeleton_path(src_mesh->get_skeleton_path());
+
+		Ref<ArrayMesh> mesh;
+		if (!src_mesh->get_mesh()->has_mesh()) {
+			//do mesh processing
+		}
+		mesh = src_mesh->get_mesh()->get_mesh();
+		mesh_node->set_mesh(mesh);
+		for (int i = 0; i < mesh->get_surface_count(); i++) {
+			mesh_node->set_surface_material(i, src_mesh->get_surface_material(i));
+		}
+
+		p_node->replace_by(mesh_node);
+		memdelete(p_node);
+		p_node = mesh_node;
+	}
+
+	for (int i = 0; i < p_node->get_child_count(); i++) {
+		_generate_meshes(p_node->get_child(i));
+	}
+}
 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) {
 	const String &src_path = p_source_file;
 
@@ -1315,6 +1641,8 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 		scene->set_name(p_save_path.get_file().get_basename());
 	}
 
+	_generate_meshes(scene);
+
 	err = OK;
 
 	String animation_filter = String(p_options["animation/filter_script"]).strip_edges();
diff --git a/editor/import/resource_importer_scene.h b/editor/import/resource_importer_scene.h
index cd61ec01f2..758390b367 100644
--- a/editor/import/resource_importer_scene.h
+++ b/editor/import/resource_importer_scene.h
@@ -32,9 +32,11 @@
 #define RESOURCEIMPORTERSCENE_H
 
 #include "core/io/resource_importer.h"
+#include "scene/3d/node_3d.h"
 #include "scene/resources/animation.h"
 #include "scene/resources/mesh.h"
 #include "scene/resources/shape_3d.h"
+#include "scene/resources/skin.h"
 
 class Material;
 
@@ -88,6 +90,90 @@ public:
 	EditorScenePostImport();
 };
 
+// The following classes are used by importers instead of ArrayMesh and MeshInstance3D
+// so the data is not reginstered (hence, quality loss), importing happens faster and
+// its easier to modify before saving
+
+class EditorSceneImporterMesh : public Resource {
+	GDCLASS(EditorSceneImporterMesh, Resource)
+
+	struct Surface {
+		Mesh::PrimitiveType primitive;
+		Array arrays;
+		struct BlendShape {
+			Array arrays;
+		};
+		Vector<BlendShape> blend_shape_data;
+		struct LOD {
+			Vector<int> indices;
+			float distance;
+		};
+		Vector<LOD> lods;
+		Ref<Material> material;
+		String name;
+	};
+	Vector<Surface> surfaces;
+	Vector<String> blend_shapes;
+	Mesh::BlendShapeMode blend_shape_mode = Mesh::BLEND_SHAPE_MODE_NORMALIZED;
+
+	Ref<ArrayMesh> mesh;
+
+protected:
+	void _set_data(const Dictionary &p_data);
+	Dictionary _get_data() const;
+
+	static void _bind_methods();
+
+public:
+	void add_blend_shape(const String &p_name);
+	int get_blend_shape_count() const;
+	String get_blend_shape_name(int p_blend_shape) const;
+
+	void add_surface(Mesh::PrimitiveType p_primitive, const Array &p_arrays, const Array &p_blend_shapes = Array(), const Dictionary &p_lods = Dictionary(), const Ref<Material> &p_material = Ref<Material>(), const String &p_name = String());
+	int get_surface_count() const;
+
+	void set_blend_shape_mode(Mesh::BlendShapeMode p_blend_shape_mode);
+	Mesh::BlendShapeMode get_blend_shape_mode() const;
+
+	Mesh::PrimitiveType get_surface_primitive_type(int p_surface);
+	String get_surface_name(int p_surface) const;
+	Array get_surface_arrays(int p_surface) const;
+	Array get_surface_blend_shape_arrays(int p_surface, int p_blend_shape) const;
+	int get_surface_lod_count(int p_surface) const;
+	Vector<int> get_surface_lod_indices(int p_surface, int p_lod) const;
+	float get_surface_lod_size(int p_surface, int p_lod) const;
+	Ref<Material> get_surface_material(int p_surface) const;
+
+	bool has_mesh() const;
+	Ref<ArrayMesh> get_mesh();
+	void clear();
+};
+
+class EditorSceneImporterMeshNode : public Node3D {
+	GDCLASS(EditorSceneImporterMeshNode, Node3D)
+
+	Ref<EditorSceneImporterMesh> mesh;
+	Ref<Skin> skin;
+	NodePath skeleton_path;
+	Vector<Ref<Material>> surface_materials;
+
+protected:
+	static void _bind_methods();
+
+public:
+	void set_mesh(const Ref<EditorSceneImporterMesh> &p_mesh);
+	Ref<EditorSceneImporterMesh> get_mesh() const;
+
+	void set_skin(const Ref<Skin> &p_skin);
+	Ref<Skin> get_skin() const;
+
+	void set_surface_material(int p_idx, const Ref<Material> &p_material);
+	Ref<Material> get_surface_material(int p_idx) const;
+
+	void set_skeleton_path(const NodePath &p_path);
+	NodePath get_skeleton_path() const;
+};
+
 class ResourceImporterScene : public ResourceImporter {
 	GDCLASS(ResourceImporterScene, ResourceImporter);
 
@@ -119,6 +205,7 @@ class ResourceImporterScene : public ResourceImporter {
 	};
 
 	void _replace_owner(Node *p_node, Node *p_scene, Node *p_new_owner);
+	void _generate_meshes(Node *p_node);
 
 public:
 	static ResourceImporterScene *get_singleton() { return singleton; }