add support for visualizing bones in Advanced Import Settings

When an imported model Skeleton3D type node is selected, the bones are drawn using lines or octahedrons to provide a clearer reference to their position.
Refactored Skeleton3DGizmoPlugin::redraw now uses a static function to generate bone meshes

4 files changed, 68 insertions, 29 deletions

diff --git a/editor/import/3d/scene_import_settings.cpp b/editor/import/3d/scene_import_settings.cpp
index 7cd5279b63..955eb8a8dc 100644
--- a/editor/import/3d/scene_import_settings.cpp
+++ b/editor/import/3d/scene_import_settings.cpp
@@ -37,6 +37,7 @@
 #include "editor/editor_settings.h"
 #include "editor/editor_string_names.h"
 #include "editor/gui/editor_file_dialog.h"
+#include "editor/plugins/skeleton_3d_editor_plugin.h"
 #include "editor/themes/editor_scale.h"
 #include "scene/3d/importer_mesh_instance_3d.h"
 #include "scene/animation/animation_player.h"
@@ -419,7 +420,9 @@ void SceneImportSettingsDialog::_fill_scene(Node *p_node, TreeItem *p_parent_ite
 				animation_player->connect(SceneStringName(animation_finished), callable_mp(this, &SceneImportSettingsDialog::_animation_finished));
 			} else if (Object::cast_to<Skeleton3D>(p_node)) {
 				category = ResourceImporterScene::INTERNAL_IMPORT_CATEGORY_SKELETON_3D_NODE;
-				skeletons.push_back(Object::cast_to<Skeleton3D>(p_node));
+				Skeleton3D *skeleton = Object::cast_to<Skeleton3D>(p_node);
+				skeleton->connect(SNAME("tree_entered"), callable_mp(this, &SceneImportSettingsDialog::_skeleton_tree_entered).bind(skeleton));
+				skeletons.push_back(skeleton);
 			} else {
 				category = ResourceImporterScene::INTERNAL_IMPORT_CATEGORY_NODE;
 			}
@@ -480,6 +483,11 @@ void SceneImportSettingsDialog::_fill_scene(Node *p_node, TreeItem *p_parent_ite
 			contents_aabb.merge_with(aabb);
 		}
 	}
+
+	Skeleton3D *skeleton = Object::cast_to<Skeleton3D>(p_node);
+	if (skeleton) {
+		bones_mesh_preview->set_mesh(Skeleton3DGizmoPlugin::get_bones_mesh(skeleton, -1, true));
+	}
 }
 
 void SceneImportSettingsDialog::_update_scene() {
@@ -800,6 +808,7 @@ void SceneImportSettingsDialog::_select(Tree *p_from, const String &p_type, cons
 		mesh_preview->hide();
 		_reset_animation();
 
+		bones_mesh_preview->hide();
 		if (Object::cast_to<Node3D>(scene)) {
 			Object::cast_to<Node3D>(scene)->show();
 		}
@@ -834,6 +843,7 @@ void SceneImportSettingsDialog::_select(Tree *p_from, const String &p_type, cons
 				scene_import_settings_data->category = ResourceImporterScene::INTERNAL_IMPORT_CATEGORY_ANIMATION_NODE;
 			} else if (Object::cast_to<Skeleton3D>(nd.node)) {
 				scene_import_settings_data->category = ResourceImporterScene::INTERNAL_IMPORT_CATEGORY_SKELETON_3D_NODE;
+				bones_mesh_preview->show();
 			} else {
 				scene_import_settings_data->category = ResourceImporterScene::INTERNAL_IMPORT_CATEGORY_NODE;
 				scene_import_settings_data->hide_options = editing_animation;
@@ -1055,6 +1065,10 @@ void SceneImportSettingsDialog::_animation_slider_value_changed(double p_value)
 	animation_player->seek(p_value * animation_map[selected_id].animation->get_length(), true);
 }
 
+void SceneImportSettingsDialog::_skeleton_tree_entered(Skeleton3D *skeleton) {
+	bones_mesh_preview->set_skeleton_path(skeleton->get_path());
+}
+
 void SceneImportSettingsDialog::_animation_finished(const StringName &p_name) {
 	Animation::LoopMode loop_mode = animation_loop_mode;
 
@@ -1800,6 +1814,13 @@ SceneImportSettingsDialog::SceneImportSettingsDialog() {
 		collider_mat->set_albedo(Color(0.5, 0.5, 1.0));
 	}
 
+	{
+		bones_mesh_preview = memnew(MeshInstance3D);
+		bones_mesh_preview->set_cast_shadows_setting(GeometryInstance3D::SHADOW_CASTING_SETTING_OFF);
+		bones_mesh_preview->set_skeleton_path(NodePath());
+		base_viewport->add_child(bones_mesh_preview);
+	}
+
 	inspector = memnew(EditorInspector);
 	inspector->set_custom_minimum_size(Size2(300 * EDSCALE, 0));
 	inspector->connect(SNAME("property_edited"), callable_mp(this, &SceneImportSettingsDialog::_inspector_property_edited));
diff --git a/editor/import/3d/scene_import_settings.h b/editor/import/3d/scene_import_settings.h
index c2a5151432..a1c537ddc8 100644
--- a/editor/import/3d/scene_import_settings.h
+++ b/editor/import/3d/scene_import_settings.h
@@ -113,6 +113,7 @@ class SceneImportSettingsDialog : public ConfirmationDialog {
 	bool animation_pingpong = false;
 	bool previous_import_as_skeleton = false;
 	bool previous_rest_as_reset = false;
+	MeshInstance3D *bones_mesh_preview = nullptr;
 
 	Ref<StandardMaterial3D> collider_mat;
 
@@ -190,6 +191,7 @@ class SceneImportSettingsDialog : public ConfirmationDialog {
 	void _material_tree_selected();
 	void _mesh_tree_selected();
 	void _scene_tree_selected();
+	void _skeleton_tree_entered(Skeleton3D *skeleton);
 	void _cleanup();
 	void _on_light_1_switch_pressed();
 	void _on_light_2_switch_pressed();
diff --git a/editor/plugins/skeleton_3d_editor_plugin.cpp b/editor/plugins/skeleton_3d_editor_plugin.cpp
index b340dd976e..9ac5051eb2 100644
--- a/editor/plugins/skeleton_3d_editor_plugin.cpp
+++ b/editor/plugins/skeleton_3d_editor_plugin.cpp
@@ -1180,16 +1180,18 @@ int Skeleton3DEditor::get_selected_bone() const {
 	return selected_bone;
 }
 
+Skeleton3DGizmoPlugin::SelectionMaterials Skeleton3DGizmoPlugin::selection_materials;
+
 Skeleton3DGizmoPlugin::Skeleton3DGizmoPlugin() {
-	unselected_mat = Ref<StandardMaterial3D>(memnew(StandardMaterial3D));
-	unselected_mat->set_shading_mode(StandardMaterial3D::SHADING_MODE_UNSHADED);
-	unselected_mat->set_transparency(StandardMaterial3D::TRANSPARENCY_ALPHA);
-	unselected_mat->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
-	unselected_mat->set_flag(StandardMaterial3D::FLAG_SRGB_VERTEX_COLOR, true);
-	unselected_mat->set_flag(StandardMaterial3D::FLAG_DISABLE_FOG, true);
-
-	selected_mat = Ref<ShaderMaterial>(memnew(ShaderMaterial));
-	selected_sh = Ref<Shader>(memnew(Shader));
+	selection_materials.unselected_mat.instantiate();
+	selection_materials.unselected_mat->set_shading_mode(StandardMaterial3D::SHADING_MODE_UNSHADED);
+	selection_materials.unselected_mat->set_transparency(StandardMaterial3D::TRANSPARENCY_ALPHA);
+	selection_materials.unselected_mat->set_flag(StandardMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
+	selection_materials.unselected_mat->set_flag(StandardMaterial3D::FLAG_SRGB_VERTEX_COLOR, true);
+	selection_materials.unselected_mat->set_flag(StandardMaterial3D::FLAG_DISABLE_FOG, true);
+
+	selection_materials.selected_mat.instantiate();
+	Ref<Shader> selected_sh = Ref<Shader>(memnew(Shader));
 	selected_sh->set_code(R"(
 // Skeleton 3D gizmo bones shader.
 
@@ -1208,7 +1210,7 @@ void fragment() {
 	ALPHA = COLOR.a;
 }
 )");
-	selected_mat->set_shader(selected_sh);
+	selection_materials.selected_mat->set_shader(selected_sh);
 
 	// Register properties in editor settings.
 	EDITOR_DEF_RST("editors/3d_gizmos/gizmo_colors/skeleton", Color(1, 0.8, 0.4));
@@ -1218,6 +1220,11 @@ void fragment() {
 	EditorSettings::get_singleton()->add_property_hint(PropertyInfo(Variant::INT, "editors/3d_gizmos/gizmo_settings/bone_shape", PROPERTY_HINT_ENUM, "Wire,Octahedron"));
 }
 
+Skeleton3DGizmoPlugin::~Skeleton3DGizmoPlugin() {
+	selection_materials.unselected_mat.unref();
+	selection_materials.selected_mat.unref();
+}
+
 bool Skeleton3DGizmoPlugin::has_gizmo(Node3D *p_spatial) {
 	return Object::cast_to<Skeleton3D>(p_spatial) != nullptr;
 }
@@ -1354,6 +1361,11 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 		selected = se->get_selected_bone();
 	}
 
+	Ref<ArrayMesh> m = get_bones_mesh(skeleton, selected, p_gizmo->is_selected());
+	p_gizmo->add_mesh(m, Ref<Material>(), Transform3D(), skeleton->register_skin(skeleton->create_skin_from_rest_transforms()));
+}
+
+Ref<ArrayMesh> Skeleton3DGizmoPlugin::get_bones_mesh(Skeleton3D *p_skeleton, int p_selected, bool p_is_selected) {
 	Color bone_color = EDITOR_GET("editors/3d_gizmos/gizmo_colors/skeleton");
 	Color selected_bone_color = EDITOR_GET("editors/3d_gizmos/gizmo_colors/selected_bone");
 	real_t bone_axis_length = EDITOR_GET("editors/3d_gizmos/gizmo_settings/bone_axis_length");
@@ -1367,11 +1379,11 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 	Ref<SurfaceTool> surface_tool(memnew(SurfaceTool));
 	surface_tool->begin(Mesh::PRIMITIVE_LINES);
 
-	if (p_gizmo->is_selected()) {
-		surface_tool->set_material(selected_mat);
+	if (p_is_selected) {
+		surface_tool->set_material(selection_materials.selected_mat);
 	} else {
-		unselected_mat->set_albedo(bone_color);
-		surface_tool->set_material(unselected_mat);
+		selection_materials.unselected_mat->set_albedo(bone_color);
+		surface_tool->set_material(selection_materials.unselected_mat);
 	}
 
 	LocalVector<int> bones;
@@ -1385,16 +1397,16 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 	weights[0] = 1;
 
 	int current_bone_index = 0;
-	Vector<int> bones_to_process = skeleton->get_parentless_bones();
+	Vector<int> bones_to_process = p_skeleton->get_parentless_bones();
 
 	while (bones_to_process.size() > current_bone_index) {
 		int current_bone_idx = bones_to_process[current_bone_index];
 		current_bone_index++;
 
-		Color current_bone_color = (current_bone_idx == selected) ? selected_bone_color : bone_color;
+		Color current_bone_color = (current_bone_idx == p_selected) ? selected_bone_color : bone_color;
 
 		Vector<int> child_bones_vector;
-		child_bones_vector = skeleton->get_bone_children(current_bone_idx);
+		child_bones_vector = p_skeleton->get_bone_children(current_bone_idx);
 		int child_bones_size = child_bones_vector.size();
 
 		for (int i = 0; i < child_bones_size; i++) {
@@ -1405,8 +1417,8 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 
 			int child_bone_idx = child_bones_vector[i];
 
-			Vector3 v0 = skeleton->get_bone_global_rest(current_bone_idx).origin;
-			Vector3 v1 = skeleton->get_bone_global_rest(child_bone_idx).origin;
+			Vector3 v0 = p_skeleton->get_bone_global_rest(current_bone_idx).origin;
+			Vector3 v1 = p_skeleton->get_bone_global_rest(child_bone_idx).origin;
 			Vector3 d = (v1 - v0).normalized();
 			real_t dist = v0.distance_to(v1);
 
@@ -1414,7 +1426,7 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 			int closest = -1;
 			real_t closest_d = 0.0;
 			for (int j = 0; j < 3; j++) {
-				real_t dp = Math::abs(skeleton->get_bone_global_rest(current_bone_idx).basis[j].normalized().dot(d));
+				real_t dp = Math::abs(p_skeleton->get_bone_global_rest(current_bone_idx).basis[j].normalized().dot(d));
 				if (j == 0 || dp > closest_d) {
 					closest = j;
 				}
@@ -1441,7 +1453,7 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 					for (int j = 0; j < 3; j++) {
 						Vector3 axis;
 						if (first == Vector3()) {
-							axis = d.cross(d.cross(skeleton->get_bone_global_rest(current_bone_idx).basis[j])).normalized();
+							axis = d.cross(d.cross(p_skeleton->get_bone_global_rest(current_bone_idx).basis[j])).normalized();
 							first = axis;
 						} else {
 							axis = d.cross(first).normalized();
@@ -1496,7 +1508,7 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 				surface_tool->add_vertex(v0);
 				surface_tool->set_bones(bones);
 				surface_tool->set_weights(weights);
-				surface_tool->add_vertex(v0 + (skeleton->get_bone_global_rest(current_bone_idx).basis.inverse())[j].normalized() * dist * bone_axis_length);
+				surface_tool->add_vertex(v0 + (p_skeleton->get_bone_global_rest(current_bone_idx).basis.inverse())[j].normalized() * dist * bone_axis_length);
 
 				if (j == closest) {
 					continue;
@@ -1513,7 +1525,7 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 					surface_tool->add_vertex(v1);
 					surface_tool->set_bones(bones);
 					surface_tool->set_weights(weights);
-					surface_tool->add_vertex(v1 + (skeleton->get_bone_global_rest(child_bone_idx).basis.inverse())[j].normalized() * dist * bone_axis_length);
+					surface_tool->add_vertex(v1 + (p_skeleton->get_bone_global_rest(child_bone_idx).basis.inverse())[j].normalized() * dist * bone_axis_length);
 
 					if (j == closest) {
 						continue;
@@ -1526,6 +1538,5 @@ void Skeleton3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 		}
 	}
 
-	Ref<ArrayMesh> m = surface_tool->commit();
-	p_gizmo->add_mesh(m, Ref<Material>(), Transform3D(), skeleton->register_skin(skeleton->create_skin_from_rest_transforms()));
+	return surface_tool->commit();
 }
diff --git a/editor/plugins/skeleton_3d_editor_plugin.h b/editor/plugins/skeleton_3d_editor_plugin.h
index 79dc16ae2f..42beb842a7 100644
--- a/editor/plugins/skeleton_3d_editor_plugin.h
+++ b/editor/plugins/skeleton_3d_editor_plugin.h
@@ -252,11 +252,15 @@ public:
 class Skeleton3DGizmoPlugin : public EditorNode3DGizmoPlugin {
 	GDCLASS(Skeleton3DGizmoPlugin, EditorNode3DGizmoPlugin);
 
-	Ref<StandardMaterial3D> unselected_mat;
-	Ref<ShaderMaterial> selected_mat;
-	Ref<Shader> selected_sh;
+	struct SelectionMaterials {
+		Ref<StandardMaterial3D> unselected_mat;
+		Ref<ShaderMaterial> selected_mat;
+	};
+	static SelectionMaterials selection_materials;
 
 public:
+	static Ref<ArrayMesh> get_bones_mesh(Skeleton3D *p_skeleton, int p_selected, bool p_is_selected);
+
 	bool has_gizmo(Node3D *p_spatial) override;
 	String get_gizmo_name() const override;
 	int get_priority() const override;
@@ -269,6 +273,7 @@ public:
 	void redraw(EditorNode3DGizmo *p_gizmo) override;
 
 	Skeleton3DGizmoPlugin();
+	~Skeleton3DGizmoPlugin();
 };
 
 #endif // SKELETON_3D_EDITOR_PLUGIN_H