LOD: Remove "Raycast Normals" and associated "Normal Split Angle" settings

"Raycast Normals" was introduced in 4.4 dev and defaulted to "false".
The limited testing results at the time suggested that raycasting
generally reduces normal quality compared to native simplifier results,
at the same time increasing vertex memory and import time.

To play it safe, we introduced a setting that defaulted to false, with
the goal of removing it later in 4.4 development cycle if no regressions
are noticed. Since we already had three dev snapshots and no reports,
this change removes the setting and associated code.

"Normal Split Angle" was only used when raycast normals were enabled;
this change removes it from the settings, but keeps it in the script
binding for compatibility.

Existing meshes import exactly the same after this change (unless they
chose to override raycasting which would be surprising).

split_normals helper was only used in this code path and is also removed
for simplicity; it is unlikely that this code will be useful as is, as
it can only regenerate normals without fixing tangents or updating
positions.

Author: zeux

doc/classes/ImporterMesh.xml

@@ -49,7 +49,8 @@
 			<param index="2" name="bone_transform_array" type="Array" />
 			<description>
 				Generates all lods for this ImporterMesh.
-				[param normal_merge_angle] and [param normal_split_angle] are in degrees and used in the same way as the importer settings in [code]lods[/code]. As a good default, use 25 and 60 respectively.
+				[param normal_merge_angle] is in degrees and used in the same way as the importer settings in [code]lods[/code].
+				[param normal_split_angle] is not used and only remains for compatibility with older versions of the API.
 				The number of generated lods can be accessed using [method get_surface_lod_count], and each LOD is available in [method get_surface_lod_size] and [method get_surface_lod_indices].
 				[param bone_transform_array] is an [Array] which can be either empty or contain [Transform3D]s which, for each of the mesh's bone IDs, will apply mesh skinning when generating the LOD mesh variations. This is usually used to account for discrepancies in scale between the mesh itself and its skinning data.
 			</description>

editor/import/3d/resource_importer_obj.cpp

@@ -539,7 +539,7 @@ static Error _parse_obj(const String &p_path, List<Ref<ImporterMesh>> &r_meshes,
 
 	if (p_generate_lods) {
 		// Use normal merge/split angles that match the defaults used for 3D scene importing.
-		mesh->generate_lods(60.0f, 25.0f, {});
+		mesh->generate_lods(60.0f, {});
 	}
 
 	if (p_generate_shadow_mesh) {

editor/import/3d/resource_importer_scene.cpp

@@ -2043,9 +2043,7 @@ void ResourceImporterScene::get_internal_import_options(InternalImportCategory p
 			r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "generate/shadow_meshes", PROPERTY_HINT_ENUM, "Default,Enable,Disable"), 0));
 			r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "generate/lightmap_uv", PROPERTY_HINT_ENUM, "Default,Enable,Disable"), 0));
 			r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "generate/lods", PROPERTY_HINT_ENUM, "Default,Enable,Disable"), 0));
-			r_options->push_back(ImportOption(PropertyInfo(Variant::FLOAT, "lods/normal_split_angle", PROPERTY_HINT_RANGE, "0,180,0.1,degrees"), 25.0f));
 			r_options->push_back(ImportOption(PropertyInfo(Variant::FLOAT, "lods/normal_merge_angle", PROPERTY_HINT_RANGE, "0,180,0.1,degrees"), 60.0f));
-			r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "lods/raycast_normals", PROPERTY_HINT_NONE, ""), false));
 		} break;
 		case INTERNAL_IMPORT_CATEGORY_MATERIAL: {
 			r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "use_external/enabled", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_UPDATE_ALL_IF_MODIFIED), false));
@@ -2474,9 +2472,7 @@ Node *ResourceImporterScene::_generate_meshes(Node *p_node, const Dictionary &p_
 				//do mesh processing
 
 				bool generate_lods = p_generate_lods;
-				float split_angle = 25.0f;
 				float merge_angle = 60.0f;
-				bool raycast_normals = false;
 				bool create_shadow_meshes = p_create_shadow_meshes;
 				bool bake_lightmaps = p_light_bake_mode == LIGHT_BAKE_STATIC_LIGHTMAPS;
 				String save_to_file;
@@ -2523,18 +2519,10 @@ Node *ResourceImporterScene::_generate_meshes(Node *p_node, const Dictionary &p_
 						}
 					}
 
-					if (mesh_settings.has("lods/normal_split_angle")) {
-						split_angle = mesh_settings["lods/normal_split_angle"];
-					}
-
 					if (mesh_settings.has("lods/normal_merge_angle")) {
 						merge_angle = mesh_settings["lods/normal_merge_angle"];
 					}
 
-					if (mesh_settings.has("lods/raycast_normals")) {
-						raycast_normals = mesh_settings["lods/raycast_normals"];
-					}
-
 					if (bool(mesh_settings.get("save_to_file/enabled", false))) {
 						save_to_file = mesh_settings.get("save_to_file/path", String());
 						if (!save_to_file.is_resource_file()) {
@@ -2583,7 +2571,7 @@ Node *ResourceImporterScene::_generate_meshes(Node *p_node, const Dictionary &p_
 
 				if (generate_lods) {
 					Array skin_pose_transform_array = _get_skinned_pose_transforms(src_mesh_node);
-					src_mesh_node->get_mesh()->generate_lods(merge_angle, split_angle, skin_pose_transform_array, raycast_normals);
+					src_mesh_node->get_mesh()->generate_lods(merge_angle, skin_pose_transform_array);
 				}
 
 				if (create_shadow_meshes) {