Improvements of state machine

- Open the menu to add new animation nodes by dragging the transitions to
empty areas and automatically connecting them.
- Adds box selection to the state machine.
- Add feature to group/ungroup selected nodes in a "sub" state machine.
- Add start/end node by default. In addition, add new color to these
nodes to differentiate then.
- Add tooltip for transitions to show the connection "from -> to".
- Add new "type" of transition line when multiple transitions are
grouped.
- Add popup to connect nodes in sub state machine.
- Add dialog to select which nodes can be deleted when they are grouped.
- Add classes:
	AnimationNodeStartState
	AnimationNodeEndState
	EditorAnimationMultiTransitionEdit
- Implements disabled transition

API Changes:
- Now it's posible to add transitions between state machines,
`AnimationNodeStateMachine::add_transition` will works with relative path,
this means you can use it like this `add_transition("Idle", "Walk", tr)`
or `add_transition("Idle", "StateMachine/Shoot)`.

doc/classes/AnimationNodeStateMachine.xml

@@ -39,12 +39,6 @@
 				Adds a transition between the given nodes.
 			</description>
 		</method>
-		<method name="get_end_node" qualifiers="const">
-			<return type="String" />
-			<description>
-				Returns the graph's end node.
-			</description>
-		</method>
 		<method name="get_graph_offset" qualifiers="const">
 			<return type="Vector2" />
 			<description>
@@ -72,12 +66,6 @@
 				Returns the given node's coordinates. Used for display in the editor.
 			</description>
 		</method>
-		<method name="get_start_node" qualifiers="const">
-			<return type="String" />
-			<description>
-				Returns the graph's end node.
-			</description>
-		</method>
 		<method name="get_transition" qualifiers="const">
 			<return type="AnimationNodeStateMachineTransition" />
 			<argument index="0" name="idx" type="int" />
@@ -157,13 +145,6 @@
 			<description>
 			</description>
 		</method>
-		<method name="set_end_node">
-			<return type="void" />
-			<argument index="0" name="name" type="StringName" />
-			<description>
-				Sets the given node as the graph end point.
-			</description>
-		</method>
 		<method name="set_graph_offset">
 			<return type="void" />
 			<argument index="0" name="offset" type="Vector2" />
@@ -179,12 +160,5 @@
 				Sets the node's coordinates. Used for display in the editor.
 			</description>
 		</method>
-		<method name="set_start_node">
-			<return type="void" />
-			<argument index="0" name="name" type="StringName" />
-			<description>
-				Sets the given node as the graph start point.
-			</description>
-		</method>
 	</methods>
 </class>

editor/plugins/animation_state_machine_editor.h

@@ -50,13 +50,13 @@ class AnimationNodeStateMachineEditor : public AnimationTreeNodeEditorPlugin {
 	Button *tool_select = nullptr;
 	Button *tool_create = nullptr;
 	Button *tool_connect = nullptr;
+	Button *tool_group = nullptr;
+	Button *tool_ungroup = nullptr;
 	Popup *name_edit_popup = nullptr;
 	LineEdit *name_edit = nullptr;
 
 	HBoxContainer *tool_erase_hb = nullptr;
 	Button *tool_erase = nullptr;
-	Button *tool_autoplay = nullptr;
-	Button *tool_end = nullptr;
 
 	OptionButton *transition_mode = nullptr;
 	OptionButton *play_mode = nullptr;
@@ -64,6 +64,7 @@ class AnimationNodeStateMachineEditor : public AnimationTreeNodeEditorPlugin {
 	PanelContainer *panel = nullptr;
 
 	StringName selected_node;
+	Set<StringName> selected_nodes;
 
 	HScrollBar *h_scroll = nullptr;
 	VScrollBar *v_scroll = nullptr;
@@ -81,18 +82,31 @@ class AnimationNodeStateMachineEditor : public AnimationTreeNodeEditorPlugin {
 	static AnimationNodeStateMachineEditor *singleton;
 
 	void _state_machine_gui_input(const Ref<InputEvent> &p_event);
-	void _connection_draw(const Vector2 &p_from, const Vector2 &p_to, AnimationNodeStateMachineTransition::SwitchMode p_mode, bool p_enabled, bool p_selected, bool p_travel, bool p_auto_advance);
+	void _connection_draw(const Vector2 &p_from, const Vector2 &p_to, AnimationNodeStateMachineTransition::SwitchMode p_mode, bool p_enabled, bool p_selected, bool p_travel, bool p_auto_advance, bool p_multi_transitions);
 	void _state_machine_draw();
 	void _state_machine_pos_draw();
 
 	void _update_graph();
 
 	PopupMenu *menu = nullptr;
+	PopupMenu *connect_menu = nullptr;
+	PopupMenu *state_machine_menu = nullptr;
+	PopupMenu *end_menu = nullptr;
 	PopupMenu *animations_menu = nullptr;
 	Vector<String> animations_to_add;
+	Vector<String> nodes_to_connect;
 
 	Vector2 add_node_pos;
 
+	ConfirmationDialog *delete_window;
+	Tree *delete_tree;
+
+	bool box_selecting = false;
+	Point2 box_selecting_from;
+	Point2 box_selecting_to;
+	Rect2 box_selecting_rect;
+	Set<StringName> previous_selected;
+
 	bool dragging_selected_attempt = false;
 	bool dragging_selected = false;
 	Vector2 drag_from;
@@ -107,6 +121,7 @@ class AnimationNodeStateMachineEditor : public AnimationTreeNodeEditorPlugin {
 
 	void _add_menu_type(int p_index);
 	void _add_animation_type(int p_index);
+	void _connect_to(int p_index);
 
 	void _removed_from_graph();
 
@@ -131,12 +146,34 @@ class AnimationNodeStateMachineEditor : public AnimationTreeNodeEditorPlugin {
 		bool disabled = false;
 		bool auto_advance = false;
 		float width = 0;
+		bool selected;
+		bool travel;
+		bool hidden;
+		int transition_index;
+		Vector<TransitionLine> multi_transitions;
 	};
 
 	Vector<TransitionLine> transition_lines;
 
+	struct NodeUR {
+		StringName name;
+		Ref<AnimationNode> node;
+		Vector2 position;
+	};
+
+	struct TransitionUR {
+		StringName new_from;
+		StringName new_to;
+		StringName old_from;
+		StringName old_to;
+		Ref<AnimationNodeStateMachineTransition> transition;
+	};
+
 	StringName selected_transition_from;
 	StringName selected_transition_to;
+	int selected_transition_index;
+	TransitionLine selected_multi_transition;
+	void _add_transition(const bool p_nested_action = false);
 
 	StringName over_node;
 	int over_node_what = -1;
@@ -150,10 +187,19 @@ class AnimationNodeStateMachineEditor : public AnimationTreeNodeEditorPlugin {
 	void _clip_src_line_to_rect(Vector2 &r_from, const Vector2 &p_to, const Rect2 &p_rect);
 	void _clip_dst_line_to_rect(const Vector2 &p_from, Vector2 &r_to, const Rect2 &p_rect);
 
-	void _erase_selected();
+	void _erase_selected(const bool p_nested_action = false);
 	void _update_mode();
-	void _autoplay_selected();
-	void _end_selected();
+	void _open_menu(const Vector2 &p_position);
+	void _open_connect_menu(const Vector2 &p_position);
+	bool _create_submenu(PopupMenu *p_menu, Ref<AnimationNodeStateMachine> p_nodesm, const StringName &p_name, const StringName &p_path, bool from_root = false, Vector<Ref<AnimationNodeStateMachine>> p_parents = Vector<Ref<AnimationNodeStateMachine>>());
+	void _stop_connecting();
+
+	void _group_selected_nodes();
+	void _ungroup_selected_nodes();
+
+	void _delete_selected();
+	void _delete_all();
+	void _delete_tree_draw();
 
 	bool last_active = false;
 	StringName last_blend_from_node;
@@ -188,4 +234,26 @@ public:
 	AnimationNodeStateMachineEditor();
 };
 
+class EditorAnimationMultiTransitionEdit : public RefCounted {
+	GDCLASS(EditorAnimationMultiTransitionEdit, RefCounted);
+
+	struct Transition {
+		StringName from;
+		StringName to;
+		Ref<AnimationNodeStateMachineTransition> transition;
+	};
+
+	Vector<Transition> transitions;
+
+protected:
+	bool _set(const StringName &p_name, const Variant &p_property);
+	bool _get(const StringName &p_name, Variant &r_property) const;
+	void _get_property_list(List<PropertyInfo> *p_list) const;
+
+public:
+	void add_transition(const StringName &p_from, const StringName &p_to, Ref<AnimationNodeStateMachineTransition> p_transition);
+
+	EditorAnimationMultiTransitionEdit(){};
+};
+
 #endif // ANIMATION_STATE_MACHINE_EDITOR_H

scene/animation/animation_node_state_machine.cpp

@@ -194,16 +194,20 @@ bool AnimationNodeStateMachinePlayback::_travel(AnimationNodeStateMachine *p_sta
 
 	//build open list
 	for (int i = 0; i < p_state_machine->transitions.size(); i++) {
-		if (p_state_machine->transitions[i].from == current) {
+		if (p_state_machine->transitions[i].transition->is_disabled()) {
+			continue;
+		}
+
+		if (p_state_machine->transitions[i].local_from == current) {
 			open_list.push_back(i);
-			float cost = p_state_machine->states[p_state_machine->transitions[i].to].position.distance_to(current_pos);
+			float cost = p_state_machine->states[p_state_machine->transitions[i].local_to].position.distance_to(current_pos);
 			cost *= p_state_machine->transitions[i].transition->get_priority();
 			AStarCost ap;
 			ap.prev = current;
 			ap.distance = cost;
-			cost_map[p_state_machine->transitions[i].to] = ap;
+			cost_map[p_state_machine->transitions[i].local_to] = ap;
 
-			if (p_state_machine->transitions[i].to == p_travel) { //prematurely found it! :D
+			if (p_state_machine->transitions[i].local_to == p_travel) { //prematurely found it! :D
 				path.push_back(p_travel);
 				return true;
 			}
@@ -222,8 +226,8 @@ bool AnimationNodeStateMachinePlayback::_travel(AnimationNodeStateMachine *p_sta
 		float least_cost = 1e20;
 
 		for (List<int>::Element *E = open_list.front(); E; E = E->next()) {
-			float cost = cost_map[p_state_machine->transitions[E->get()].to].distance;
-			cost += p_state_machine->states[p_state_machine->transitions[E->get()].to].position.distance_to(target_pos);
+			float cost = cost_map[p_state_machine->transitions[E->get()].local_to].distance;
+			cost += p_state_machine->states[p_state_machine->transitions[E->get()].local_to].position.distance_to(target_pos);
 
 			if (cost < least_cost) {
 				least_cost_transition = E;
@@ -231,34 +235,38 @@ bool AnimationNodeStateMachinePlayback::_travel(AnimationNodeStateMachine *p_sta
 			}
 		}
 
-		StringName transition_prev = p_state_machine->transitions[least_cost_transition->get()].from;
-		StringName transition = p_state_machine->transitions[least_cost_transition->get()].to;
+		StringName transition_prev = p_state_machine->transitions[least_cost_transition->get()].local_from;
+		StringName transition = p_state_machine->transitions[least_cost_transition->get()].local_to;
 
 		for (int i = 0; i < p_state_machine->transitions.size(); i++) {
-			if (p_state_machine->transitions[i].from != transition || p_state_machine->transitions[i].to == transition_prev) {
+			if (p_state_machine->transitions[i].transition->is_disabled()) {
+				continue;
+			}
+
+			if (p_state_machine->transitions[i].local_from != transition || p_state_machine->transitions[i].local_to == transition_prev) {
 				continue; //not interested on those
 			}
 
-			float distance = p_state_machine->states[p_state_machine->transitions[i].from].position.distance_to(p_state_machine->states[p_state_machine->transitions[i].to].position);
+			float distance = p_state_machine->states[p_state_machine->transitions[i].local_from].position.distance_to(p_state_machine->states[p_state_machine->transitions[i].local_to].position);
 			distance *= p_state_machine->transitions[i].transition->get_priority();
-			distance += cost_map[p_state_machine->transitions[i].from].distance;
+			distance += cost_map[p_state_machine->transitions[i].local_from].distance;
 
-			if (cost_map.has(p_state_machine->transitions[i].to)) {
+			if (cost_map.has(p_state_machine->transitions[i].local_to)) {
 				//oh this was visited already, can we win the cost?
-				if (distance < cost_map[p_state_machine->transitions[i].to].distance) {
-					cost_map[p_state_machine->transitions[i].to].distance = distance;
-					cost_map[p_state_machine->transitions[i].to].prev = p_state_machine->transitions[i].from;
+				if (distance < cost_map[p_state_machine->transitions[i].local_to].distance) {
+					cost_map[p_state_machine->transitions[i].local_to].distance = distance;
+					cost_map[p_state_machine->transitions[i].local_to].prev = p_state_machine->transitions[i].local_from;
 				}
 			} else {
 				//add to open list
 				AStarCost ac;
-				ac.prev = p_state_machine->transitions[i].from;
+				ac.prev = p_state_machine->transitions[i].local_from;
 				ac.distance = distance;
-				cost_map[p_state_machine->transitions[i].to] = ac;
+				cost_map[p_state_machine->transitions[i].local_to] = ac;
 
 				open_list.push_back(i);
 
-				if (p_state_machine->transitions[i].to == p_travel) {
+				if (p_state_machine->transitions[i].local_to == p_travel) {
 					found_route = true;
 					break;
 				}
@@ -397,7 +405,11 @@ double AnimationNodeStateMachinePlayback::process(AnimationNodeStateMachine *p_s
 
 	if (path.size()) {
 		for (int i = 0; i < p_state_machine->transitions.size(); i++) {
-			if (p_state_machine->transitions[i].from == current && p_state_machine->transitions[i].to == path[0]) {
+			if (p_state_machine->transitions[i].transition->is_disabled()) {
+				continue;
+			}
+
+			if (p_state_machine->transitions[i].local_from == current && p_state_machine->transitions[i].local_to == path[0]) {
 				next_xfade = p_state_machine->transitions[i].transition->get_xfade_time();
 				switch_mode = p_state_machine->transitions[i].transition->get_switch_mode();
 				next = path[0];
@@ -406,17 +418,39 @@ double AnimationNodeStateMachinePlayback::process(AnimationNodeStateMachine *p_s
 	} else {
 		float priority_best = 1e20;
 		int auto_advance_to = -1;
+
 		for (int i = 0; i < p_state_machine->transitions.size(); i++) {
-			bool auto_advance = false;
-			if (p_state_machine->transitions[i].transition->has_auto_advance()) {
-				auto_advance = true;
+			if (p_state_machine->transitions[i].transition->is_disabled()) {
+				continue;
 			}
-			StringName advance_condition_name = p_state_machine->transitions[i].transition->get_advance_condition_name();
-			if (advance_condition_name != StringName() && bool(p_state_machine->get_parameter(advance_condition_name))) {
-				auto_advance = true;
+
+			// handles end_node: when end_node is reached in a sub state machine, find and activate the current_transition
+			if (force_auto_advance) {
+				if (p_state_machine->transitions[i].from == current_transition.from && p_state_machine->transitions[i].to == current_transition.to) {
+					auto_advance_to = i;
+					force_auto_advance = false;
+					break;
+				}
 			}
 
-			if (p_state_machine->transitions[i].from == current && auto_advance) {
+			// handles start_node: if previous state machine is pointing to a node inside the current state machine, starts the current machine from start_node to prev_local_to
+			if (p_state_machine->start_node == current && p_state_machine->transitions[i].local_from == current) {
+				if (p_state_machine->prev_state_machine.is_valid()) {
+					Ref<AnimationNodeStateMachinePlayback> prev_playback = p_state_machine->prev_state_machine->get_parameter("playback");
+
+					if (prev_playback.is_valid()) {
+						StringName prev_local_to = String(prev_playback->current_transition.next).replace_first(String(p_state_machine->state_machine_name) + "/", "");
+
+						if (p_state_machine->transitions[i].to == prev_local_to) {
+							auto_advance_to = i;
+							prev_playback->current_transition.next = StringName();
+							break;
+						}
+					}
+				}
+			}
+
+			if (p_state_machine->transitions[i].from == current && _check_advance_condition(p_state_machine, p_state_machine->transitions[i].transition)) {
 				if (p_state_machine->transitions[i].transition->get_priority() <= priority_best) {
 					priority_best = p_state_machine->transitions[i].transition->get_priority();
 					auto_advance_to = i;
@@ -425,12 +459,55 @@ double AnimationNodeStateMachinePlayback::process(AnimationNodeStateMachine *p_s
 		}
 
 		if (auto_advance_to != -1) {
-			next = p_state_machine->transitions[auto_advance_to].to;
+			next = p_state_machine->transitions[auto_advance_to].local_to;
+			Transition tr;
+			tr.from = String(p_state_machine->state_machine_name) + "/" + String(p_state_machine->transitions[auto_advance_to].from);
+			tr.to = String(p_state_machine->transitions[auto_advance_to].to).replace_first("../", "");
+			tr.next = p_state_machine->transitions[auto_advance_to].to;
+			current_transition = tr;
 			next_xfade = p_state_machine->transitions[auto_advance_to].transition->get_xfade_time();
 			switch_mode = p_state_machine->transitions[auto_advance_to].transition->get_switch_mode();
 		}
 	}
 
+	if (next == p_state_machine->end_node) {
+		Ref<AnimationNodeStateMachine> prev_state_machine = p_state_machine->prev_state_machine;
+
+		if (prev_state_machine.is_valid()) {
+			Ref<AnimationNodeStateMachinePlayback> prev_playback = prev_state_machine->get_parameter("playback");
+
+			if (prev_playback.is_valid()) {
+				if (next_xfade) {
+					prev_playback->current_transition = current_transition;
+					prev_playback->force_auto_advance = true;
+
+					return rem;
+				}
+				float priority_best = 1e20;
+				int auto_advance_to = -1;
+
+				for (int i = 0; i < prev_state_machine->transitions.size(); i++) {
+					if (prev_state_machine->transitions[i].transition->is_disabled()) {
+						continue;
+					}
+
+					if (current_transition.next == prev_state_machine->end_node && _check_advance_condition(prev_state_machine, prev_state_machine->transitions[i].transition)) {
+						if (prev_state_machine->transitions[i].transition->get_priority() <= priority_best) {
+							priority_best = prev_state_machine->transitions[i].transition->get_priority();
+							auto_advance_to = i;
+						}
+					}
+				}
+
+				if (auto_advance_to != -1) {
+					if (prev_state_machine->transitions[auto_advance_to].transition->get_xfade_time()) {
+						return rem;
+					}
+				}
+			}
+		}
+	}
+
 	//if next, see when to transition
 	if (next != StringName()) {
 		bool goto_next = false;
@@ -474,14 +551,35 @@ double AnimationNodeStateMachinePlayback::process(AnimationNodeStateMachine *p_s
 		}
 	}
 
-	//compute time left for transitions by using the end node
-	if (p_state_machine->end_node != StringName() && p_state_machine->end_node != current) {
-		rem = p_state_machine->blend_node(p_state_machine->end_node, p_state_machine->states[p_state_machine->end_node].node, 0, true, 0, AnimationNode::FILTER_IGNORE, false);
+	// time left must always be 1 because the end node don't lenght to compute
+	if (p_state_machine->end_node != current) {
+		rem = 1;
+	} else {
+		Ref<AnimationNodeStateMachinePlayback> prev_playback = p_state_machine->prev_state_machine->get_parameter("playback");
+
+		if (prev_playback.is_valid()) {
+			prev_playback->current_transition = current_transition;
+			prev_playback->force_auto_advance = true;
+		}
 	}
 
 	return rem;
 }
 
+bool AnimationNodeStateMachinePlayback::_check_advance_condition(const Ref<AnimationNodeStateMachine> state_machine, const Ref<AnimationNodeStateMachineTransition> transition) const {
+	if (transition->has_auto_advance()) {
+		return true;
+	}
+
+	StringName advance_condition_name = transition->get_advance_condition_name();
+
+	if (advance_condition_name != StringName() && bool(state_machine->get_parameter(advance_condition_name))) {
+		return true;
+	}
+
+	return false;
+}
+
 void AnimationNodeStateMachinePlayback::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("travel", "to_node"), &AnimationNodeStateMachinePlayback::travel);
 	ClassDB::bind_method(D_METHOD("start", "node"), &AnimationNodeStateMachinePlayback::start);
@@ -513,6 +611,23 @@ void AnimationNodeStateMachine::get_parameter_list(List<PropertyInfo> *r_list) c
 	for (const StringName &E : advance_conditions) {
 		r_list->push_back(PropertyInfo(Variant::BOOL, E));
 	}
+
+	// for (const KeyValue<StringName, State> &E : states) {
+	// 	if (E->node == ansm) {
+	// 		for (int i = 0; i < E->node->transitions.size(); i++) {
+	// 			StringName ac = E->node->transitions[i].transition->get_advance_condition_name();
+	// 			if (ac != StringName() && advance_conditions.find(ac) == nullptr) {
+	// 				advance_conditions.push_back(ac);
+	// 			}
+	// 		}
+
+	// 		advance_conditions.sort_custom<StringName::AlphCompare>();
+
+	// 		for (const StringName &E : advance_conditions) {
+	// 			r_list->push_back(PropertyInfo(Variant::BOOL, E));
+	// 		}
+	// 	}
+	// }
 }
 
 Variant AnimationNodeStateMachine::get_parameter_default_value(const StringName &p_parameter) const {
@@ -536,6 +651,13 @@ void AnimationNodeStateMachine::add_node(const StringName &p_name, Ref<Animation
 
 	states[p_name] = state;
 
+	Ref<AnimationNodeStateMachine> anodesm = p_node;
+
+	if (anodesm.is_valid()) {
+		anodesm->state_machine_name = p_name;
+		anodesm->prev_state_machine = (Ref<AnimationNodeStateMachine>)this;
+	}
+
 	emit_changed();
 	emit_signal(SNAME("tree_changed"));
 
@@ -562,6 +684,14 @@ void AnimationNodeStateMachine::replace_node(const StringName &p_name, Ref<Anima
 	p_node->connect("tree_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed), varray(), CONNECT_REFERENCE_COUNTED);
 }
 
+bool AnimationNodeStateMachine::can_edit_node(const StringName &p_name) const {
+	if (states.has(p_name)) {
+		return !(states[p_name].node->is_class("AnimationNodeStartState") || states[p_name].node->is_class("AnimationNodeEndState"));
+	}
+
+	return true;
+}
+
 Ref<AnimationNode> AnimationNodeStateMachine::get_node(const StringName &p_name) const {
 	ERR_FAIL_COND_V(!states.has(p_name), Ref<AnimationNode>());
 
@@ -602,36 +732,24 @@ bool AnimationNodeStateMachine::has_node(const StringName &p_name) const {
 void AnimationNodeStateMachine::remove_node(const StringName &p_name) {
 	ERR_FAIL_COND(!states.has(p_name));
 
-	{
-		Ref<AnimationNode> node = states[p_name].node;
-
-		ERR_FAIL_COND(node.is_null());
-
-		node->disconnect("tree_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed));
+	if (!can_edit_node(p_name)) {
+		return;
 	}
 
-	states.erase(p_name);
-	//path.erase(p_name);
-
 	for (int i = 0; i < transitions.size(); i++) {
-		if (transitions[i].from == p_name || transitions[i].to == p_name) {
-			transitions.write[i].transition->disconnect("advance_condition_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed));
-			transitions.remove_at(i);
+		if (transitions[i].local_from == p_name || transitions[i].local_to == p_name) {
+			remove_transition_by_index(i);
 			i--;
 		}
 	}
 
-	if (start_node == p_name) {
-		start_node = StringName();
-	}
-
-	if (end_node == p_name) {
-		end_node = StringName();
+	{
+		Ref<AnimationNode> node = states[p_name].node;
+		ERR_FAIL_COND(node.is_null());
+		node->disconnect("tree_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed));
 	}
 
-	/*if (playing && current == p_name) {
-		stop();
-	}*/
+	states.erase(p_name);
 
 	emit_changed();
 	emit_signal(SNAME("tree_changed"));
@@ -640,39 +758,73 @@ void AnimationNodeStateMachine::remove_node(const StringName &p_name) {
 void AnimationNodeStateMachine::rename_node(const StringName &p_name, const StringName &p_new_name) {
 	ERR_FAIL_COND(!states.has(p_name));
 	ERR_FAIL_COND(states.has(p_new_name));
+	ERR_FAIL_COND(!can_edit_node(p_name));
 
 	states[p_new_name] = states[p_name];
 	states.erase(p_name);
 
+	Ref<AnimationNodeStateMachine> anodesm = states[p_new_name].node;
+	if (anodesm.is_valid()) {
+		anodesm->state_machine_name = p_new_name;
+	}
+
 	for (int i = 0; i < transitions.size(); i++) {
-		if (transitions[i].from == p_name) {
-			transitions.write[i].from = p_new_name;
+		if (transitions[i].local_from == p_name) {
+			_rename_transition(transitions[i].from, String(transitions[i].from).replace_first(p_name, p_new_name));
 		}
 
-		if (transitions[i].to == p_name) {
-			transitions.write[i].to = p_new_name;
+		if (transitions[i].local_to == p_name) {
+			_rename_transition(transitions[i].to, String(transitions[i].to).replace_first(p_name, p_new_name));
 		}
 	}
 
-	if (start_node == p_name) {
-		start_node = p_new_name;
-	}
+	emit_signal("tree_changed");
+}
 
-	if (end_node == p_name) {
-		end_node = p_new_name;
+void AnimationNodeStateMachine::_rename_transition(const StringName &p_name, const StringName &p_new_name) {
+	if (updating_transitions) {
+		return;
 	}
 
-	/*if (playing && current == p_name) {
-		current = p_new_name;
-	}*/
+	updating_transitions = true;
+	for (int i = 0; i < transitions.size(); i++) {
+		if (transitions[i].from == p_name) {
+			Vector<String> path = String(transitions[i].to).split("/");
+			if (path.size() > 1) {
+				if (path[0] == "..") {
+					prev_state_machine->_rename_transition(String(state_machine_name) + "/" + p_name, String(state_machine_name) + "/" + p_new_name);
+				} else {
+					((Ref<AnimationNodeStateMachine>)states[transitions[i].local_to].node)->_rename_transition("../" + p_name, "../" + p_new_name);
+				}
+			}
+
+			transitions.write[i].from = p_new_name;
+		}
 
-	//path.clear(); //clear path
-	emit_signal(SNAME("tree_changed"));
+		if (transitions[i].to == p_name) {
+			Vector<String> path = String(transitions[i].from).split("/");
+			if (path.size() > 1) {
+				if (path[0] == "..") {
+					prev_state_machine->_rename_transition(String(state_machine_name) + "/" + p_name, String(state_machine_name) + "/" + p_new_name);
+				} else {
+					((Ref<AnimationNodeStateMachine>)states[transitions[i].local_from].node)->_rename_transition("../" + p_name, "../" + p_new_name);
+				}
+			}
+
+			transitions.write[i].to = p_new_name;
+		}
+
+		updating_transitions = false;
+	}
 }
 
 void AnimationNodeStateMachine::get_node_list(List<StringName> *r_nodes) const {
 	List<StringName> nodes;
 	for (const KeyValue<StringName, State> &E : states) {
+		if (E.key == end_node && !prev_state_machine.is_valid()) {
+			continue;
+		}
+
 		nodes.push_back(E.key);
 	}
 	nodes.sort_custom<StringName::AlphCompare>();
@@ -682,9 +834,16 @@ void AnimationNodeStateMachine::get_node_list(List<StringName> *r_nodes) const {
 	}
 }
 
+Ref<AnimationNodeStateMachine> AnimationNodeStateMachine::get_prev_state_machine() const {
+	return prev_state_machine;
+}
+
 bool AnimationNodeStateMachine::has_transition(const StringName &p_from, const StringName &p_to) const {
+	StringName from = _get_shortest_path(p_from);
+	StringName to = _get_shortest_path(p_to);
+
 	for (int i = 0; i < transitions.size(); i++) {
-		if (transitions[i].from == p_from && transitions[i].to == p_to) {
+		if (transitions[i].from == from && transitions[i].to == to) {
 			return true;
 		}
 	}
@@ -692,32 +851,148 @@ bool AnimationNodeStateMachine::has_transition(const StringName &p_from, const S
 }
 
 int AnimationNodeStateMachine::find_transition(const StringName &p_from, const StringName &p_to) const {
+	StringName from = _get_shortest_path(p_from);
+	StringName to = _get_shortest_path(p_to);
+
 	for (int i = 0; i < transitions.size(); i++) {
-		if (transitions[i].from == p_from && transitions[i].to == p_to) {
+		if (transitions[i].from == from && transitions[i].to == to) {
 			return i;
 		}
 	}
 	return -1;
 }
 
+bool AnimationNodeStateMachine::_can_connect(const StringName &p_name, Vector<Ref<AnimationNodeStateMachine>> p_parents) const {
+	if (p_parents.is_empty()) {
+		Ref<AnimationNodeStateMachine> prev = (Ref<AnimationNodeStateMachine>)this;
+		while (prev.is_valid()) {
+			p_parents.push_back(prev);
+			prev = prev->prev_state_machine;
+		}
+	}
+
+	if (states.has(p_name)) {
+		Ref<AnimationNodeStateMachine> anodesm = states[p_name].node;
+
+		if (anodesm.is_valid() && p_parents.find(anodesm) != -1) {
+			return false;
+		}
+
+		return true;
+	}
+
+	String name = p_name;
+	Vector<String> path = name.split("/");
+
+	if (path.size() < 2) {
+		return false;
+	}
+
+	if (path[0] == "..") {
+		if (prev_state_machine.is_valid()) {
+			return prev_state_machine->_can_connect(name.replace_first("../", ""), p_parents);
+		}
+	} else if (states.has(path[0])) {
+		Ref<AnimationNodeStateMachine> anodesm = states[path[0]].node;
+		if (anodesm.is_valid()) {
+			return anodesm->_can_connect(name.replace_first(path[0] + "/", ""), p_parents);
+		}
+	}
+
+	return false;
+}
+
+StringName AnimationNodeStateMachine::_get_shortest_path(const StringName &p_path) const {
+	// If p_path is something like StateMachine/../StateMachine2/State1,
+	// the result will be StateMachine2/State1. This avoid duplicate
+	// transitions when using add_transition. eg, this two calls is the same:
+	//
+	// add_transition("State1", "StateMachine/../State2", tr)
+	// add_transition("State1", "State2", tr)
+	//
+	// but the second call must be invalid because the transition already exists
+
+	Vector<String> path = String(p_path).split("/");
+	Vector<String> new_path;
+
+	for (int i = 0; i < path.size(); i++) {
+		if (i > 0 && path[i] == ".." && new_path[i - 1] != "..") {
+			new_path.remove_at(i - 1);
+		} else {
+			new_path.push_back(path[i]);
+		}
+	}
+
+	String result;
+	for (int i = 0; i < new_path.size(); i++) {
+		result += new_path[i] + "/";
+	}
+	result.remove_at(result.length() - 1);
+
+	return result;
+}
+
 void AnimationNodeStateMachine::add_transition(const StringName &p_from, const StringName &p_to, const Ref<AnimationNodeStateMachineTransition> &p_transition) {
-	ERR_FAIL_COND(p_from == p_to);
-	ERR_FAIL_COND(!states.has(p_from));
-	ERR_FAIL_COND(!states.has(p_to));
+	if (updating_transitions) {
+		return;
+	}
+
+	StringName from = _get_shortest_path(p_from);
+	StringName to = _get_shortest_path(p_to);
+	Vector<String> path_from = String(from).split("/");
+	Vector<String> path_to = String(to).split("/");
+
+	ERR_FAIL_COND(from == end_node || to == start_node);
+	ERR_FAIL_COND(from == to);
+	ERR_FAIL_COND(!_can_connect(from));
+	ERR_FAIL_COND(!_can_connect(to));
 	ERR_FAIL_COND(p_transition.is_null());
 
 	for (int i = 0; i < transitions.size(); i++) {
-		ERR_FAIL_COND(transitions[i].from == p_from && transitions[i].to == p_to);
+		ERR_FAIL_COND(transitions[i].from == from && transitions[i].to == to);
 	}
 
+	if (path_from.size() > 1 || path_to.size() > 1) {
+		ERR_FAIL_COND(path_from[0] == path_to[0]);
+	}
+
+	updating_transitions = true;
+
+	StringName local_from = String(from).get_slicec('/', 0);
+	StringName local_to = String(to).get_slicec('/', 0);
+	local_from = local_from == ".." ? "Start" : local_from;
+	local_to = local_to == ".." ? "End" : local_to;
+
 	Transition tr;
-	tr.from = p_from;
-	tr.to = p_to;
+	tr.from = from;
+	tr.to = to;
+	tr.local_from = local_from;
+	tr.local_to = local_to;
 	tr.transition = p_transition;
 
 	tr.transition->connect("advance_condition_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed), varray(), CONNECT_REFERENCE_COUNTED);
 
 	transitions.push_back(tr);
+
+	// do recursive
+	if (path_from.size() > 1) {
+		StringName local_path = String(from).replace_first(path_from[0] + "/", "");
+		if (path_from[0] == "..") {
+			prev_state_machine->add_transition(local_path, String(state_machine_name) + "/" + to, p_transition);
+		} else {
+			((Ref<AnimationNodeStateMachine>)states[path_from[0]].node)->add_transition(local_path, "../" + to, p_transition);
+		}
+	}
+	if (path_to.size() > 1) {
+		StringName local_path = String(to).replace_first(path_to[0] + "/", "");
+		if (path_to[0] == "..") {
+			prev_state_machine->add_transition(String(state_machine_name) + "/" + from, local_path, p_transition);
+		} else {
+			((Ref<AnimationNodeStateMachine>)states[path_to[0]].node)->add_transition("../" + from, local_path, p_transition);
+		}
+	}
+
+	updating_transitions = false;
 }
 
 Ref<AnimationNodeStateMachineTransition> AnimationNodeStateMachine::get_transition(int p_transition) const {
@@ -740,44 +1015,52 @@ int AnimationNodeStateMachine::get_transition_count() const {
 }
 
 void AnimationNodeStateMachine::remove_transition(const StringName &p_from, const StringName &p_to) {
+	StringName from = _get_shortest_path(p_from);
+	StringName to = _get_shortest_path(p_to);
+
 	for (int i = 0; i < transitions.size(); i++) {
-		if (transitions[i].from == p_from && transitions[i].to == p_to) {
-			transitions.write[i].transition->disconnect("advance_condition_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed));
-			transitions.remove_at(i);
+		if (transitions[i].from == from && transitions[i].to == to) {
+			remove_transition_by_index(i);
 			return;
 		}
 	}
-
-	/*if (playing) {
-		path.clear();
-	}*/
 }
 
-void AnimationNodeStateMachine::remove_transition_by_index(int p_transition) {
+void AnimationNodeStateMachine::remove_transition_by_index(const int p_transition) {
 	ERR_FAIL_INDEX(p_transition, transitions.size());
+	Transition tr = transitions[p_transition];
 	transitions.write[p_transition].transition->disconnect("advance_condition_changed", callable_mp(this, &AnimationNodeStateMachine::_tree_changed));
 	transitions.remove_at(p_transition);
-	/*if (playing) {
-		path.clear();
-	}*/
-}
 
-void AnimationNodeStateMachine::set_start_node(const StringName &p_node) {
-	ERR_FAIL_COND(p_node != StringName() && !states.has(p_node));
-	start_node = p_node;
-}
+	Vector<String> path_from = String(tr.from).split("/");
+	Vector<String> path_to = String(tr.to).split("/");
 
-String AnimationNodeStateMachine::get_start_node() const {
-	return start_node;
-}
+	List<Vector<String>> paths;
+	paths.push_back(path_from);
+	paths.push_back(path_to);
 
-void AnimationNodeStateMachine::set_end_node(const StringName &p_node) {
-	ERR_FAIL_COND(p_node != StringName() && !states.has(p_node));
-	end_node = p_node;
+	for (List<Vector<String>>::Element *E = paths.front(); E; E = E->next()) {
+		if (E->get()[0].size() > 1) {
+			if (E->get()[0] == "..") {
+				prev_state_machine->_remove_transition(tr.transition);
+			} else if (states.has(E->get()[0])) {
+				Ref<AnimationNodeStateMachine> anodesm = states[E->get()[0]].node;
+
+				if (anodesm.is_valid()) {
+					anodesm->_remove_transition(tr.transition);
+				}
+			}
+		}
+	}
 }
 
-String AnimationNodeStateMachine::get_end_node() const {
-	return end_node;
+void AnimationNodeStateMachine::_remove_transition(const Ref<AnimationNodeStateMachineTransition> p_transition) {
+	for (int i = 0; i < transitions.size(); i++) {
+		if (transitions[i].transition == p_transition) {
+			remove_transition_by_index(i);
+			return;
+		}
+	}
 }
 
 void AnimationNodeStateMachine::set_graph_offset(const Vector2 &p_offset) {
@@ -799,6 +1082,18 @@ String AnimationNodeStateMachine::get_caption() const {
 	return "StateMachine";
 }
 
+bool AnimationNodeStateMachine::has_local_transition(const StringName &p_from, const StringName &p_to) const {
+	StringName from = _get_shortest_path(p_from);
+	StringName to = _get_shortest_path(p_to);
+
+	for (int i = 0; i < transitions.size(); i++) {
+		if (transitions[i].local_from == from && transitions[i].local_to == to) {
+			return true;
+		}
+	}
+	return false;
+}
+
 Ref<AnimationNode> AnimationNodeStateMachine::get_child_by_name(const StringName &p_name) {
 	return get_node(p_name);
 }
@@ -831,12 +1126,6 @@ bool AnimationNodeStateMachine::_set(const StringName &p_name, const Variant &p_
 			add_transition(trans[i], trans[i + 1], trans[i + 2]);
 		}
 		return true;
-	} else if (name == "start_node") {
-		set_start_node(p_value);
-		return true;
-	} else if (name == "end_node") {
-		set_end_node(p_value);
-		return true;
 	} else if (name == "graph_offset") {
 		set_graph_offset(p_value);
 		return true;
@@ -852,7 +1141,7 @@ bool AnimationNodeStateMachine::_get(const StringName &p_name, Variant &r_ret) c
 		String what = name.get_slicec('/', 2);
 
 		if (what == "node") {
-			if (states.has(node_name)) {
+			if (states.has(node_name) && can_edit_node(node_name)) {
 				r_ret = states[node_name].node;
 				return true;
 			}
@@ -866,22 +1155,21 @@ bool AnimationNodeStateMachine::_get(const StringName &p_name, Variant &r_ret) c
 		}
 	} else if (name == "transitions") {
 		Array trans;
-		trans.resize(transitions.size() * 3);
-
 		for (int i = 0; i < transitions.size(); i++) {
-			trans[i * 3 + 0] = transitions[i].from;
-			trans[i * 3 + 1] = transitions[i].to;
-			trans[i * 3 + 2] = transitions[i].transition;
+			String from = transitions[i].from;
+			String to = transitions[i].to;
+
+			if (from.get_slicec('/', 0) == ".." || to.get_slicec('/', 0) == "..") {
+				continue;
+			}
+
+			trans.push_back(from);
+			trans.push_back(to);
+			trans.push_back(transitions[i].transition);
 		}
 
 		r_ret = trans;
 		return true;
-	} else if (name == "start_node") {
-		r_ret = get_start_node();
-		return true;
-	} else if (name == "end_node") {
-		r_ret = get_end_node();
-		return true;
 	} else if (name == "graph_offset") {
 		r_ret = get_graph_offset();
 		return true;
@@ -903,8 +1191,6 @@ void AnimationNodeStateMachine::_get_property_list(List<PropertyInfo> *p_list) c
 	}
 
 	p_list->push_back(PropertyInfo(Variant::ARRAY, "transitions", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR));
-	p_list->push_back(PropertyInfo(Variant::STRING_NAME, "start_node", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR));
-	p_list->push_back(PropertyInfo(Variant::STRING_NAME, "end_node", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR));
 	p_list->push_back(PropertyInfo(Variant::VECTOR2, "graph_offset", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR));
 }
 
@@ -912,10 +1198,24 @@ void AnimationNodeStateMachine::reset_state() {
 	states.clear();
 	transitions.clear();
 	playback = "playback";
-	start_node = StringName();
-	end_node = StringName();
+	start_node = "Start";
+	end_node = "End";
 	graph_offset = Vector2();
 
+	Ref<AnimationNodeStartState> s;
+	s.instantiate();
+	State start;
+	start.node = s;
+	start.position = Vector2(200, 100);
+	states[start_node] = start;
+
+	Ref<AnimationNodeEndState> e;
+	e.instantiate();
+	State end;
+	end.node = e;
+	end.position = Vector2(900, 100);
+	states[end_node] = end;
+
 	emit_changed();
 	emit_signal(SNAME("tree_changed"));
 }
@@ -955,15 +1255,22 @@ void AnimationNodeStateMachine::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("remove_transition_by_index", "idx"), &AnimationNodeStateMachine::remove_transition_by_index);
 	ClassDB::bind_method(D_METHOD("remove_transition", "from", "to"), &AnimationNodeStateMachine::remove_transition);
 
-	ClassDB::bind_method(D_METHOD("set_start_node", "name"), &AnimationNodeStateMachine::set_start_node);
-	ClassDB::bind_method(D_METHOD("get_start_node"), &AnimationNodeStateMachine::get_start_node);
-
-	ClassDB::bind_method(D_METHOD("set_end_node", "name"), &AnimationNodeStateMachine::set_end_node);
-	ClassDB::bind_method(D_METHOD("get_end_node"), &AnimationNodeStateMachine::get_end_node);
-
 	ClassDB::bind_method(D_METHOD("set_graph_offset", "offset"), &AnimationNodeStateMachine::set_graph_offset);
 	ClassDB::bind_method(D_METHOD("get_graph_offset"), &AnimationNodeStateMachine::get_graph_offset);
 }
 
 AnimationNodeStateMachine::AnimationNodeStateMachine() {
+	Ref<AnimationNodeStartState> s;
+	s.instantiate();
+	State start;
+	start.node = s;
+	start.position = Vector2(200, 100);
+	states[start_node] = start;
+
+	Ref<AnimationNodeEndState> e;
+	e.instantiate();
+	State end;
+	end.node = e;
+	end.position = Vector2(900, 100);
+	states[end_node] = end;
 }

scene/animation/animation_node_state_machine.h

@@ -93,13 +93,19 @@ class AnimationNodeStateMachinePlayback : public Resource {
 		StringName prev;
 	};
 
-	float len_total = 0.0;
+	struct Transition {
+		StringName from;
+		StringName to;
+		StringName next;
+	};
 
 	float len_current = 0.0;
 	float pos_current = 0.0;
 	bool end_loop = false;
 
 	StringName current;
+	Transition current_transition;
+	bool force_auto_advance = false;
 
 	StringName fading_from;
 	float fading_time = 0.0;
@@ -116,6 +122,8 @@ class AnimationNodeStateMachinePlayback : public Resource {
 
 	double process(AnimationNodeStateMachine *p_state_machine, double p_time, bool p_seek);
 
+	bool _check_advance_condition(const Ref<AnimationNodeStateMachine> p_state_machine, const Ref<AnimationNodeStateMachineTransition> p_transition) const;
+
 protected:
 	static void _bind_methods();
 
@@ -149,19 +157,25 @@ private:
 	struct Transition {
 		StringName from;
 		StringName to;
+		StringName local_from;
+		StringName local_to;
 		Ref<AnimationNodeStateMachineTransition> transition;
 	};
 
 	Vector<Transition> transitions;
 
 	StringName playback = "playback";
-
-	StringName start_node;
-	StringName end_node;
+	StringName state_machine_name;
+	Ref<AnimationNodeStateMachine> prev_state_machine;
+	bool updating_transitions = false;
 
 	Vector2 graph_offset;
 
 	void _tree_changed();
+	void _remove_transition(const Ref<AnimationNodeStateMachineTransition> p_transition);
+	void _rename_transition(const StringName &p_name, const StringName &p_new_name);
+	bool _can_connect(const StringName &p_name, const Vector<Ref<AnimationNodeStateMachine>> p_parents = Vector<Ref<AnimationNodeStateMachine>>()) const;
+	StringName _get_shortest_path(const StringName &p_path) const;
 
 protected:
 	static void _bind_methods();
@@ -169,10 +183,14 @@ protected:
 	bool _set(const StringName &p_name, const Variant &p_value);
 	bool _get(const StringName &p_name, Variant &r_ret) const;
 	void _get_property_list(List<PropertyInfo> *p_list) const;
+	bool _check_advance_condition(const Ref<AnimationNodeStateMachine> p_state_machine, const Ref<AnimationNodeStateMachineTransition> p_transition) const;
 
 	virtual void reset_state() override;
 
 public:
+	StringName start_node = "Start";
+	StringName end_node = "End";
+
 	virtual void get_parameter_list(List<PropertyInfo> *r_list) const override;
 	virtual Variant get_parameter_default_value(const StringName &p_parameter) const override;
 
@@ -191,20 +209,19 @@ public:
 	virtual void get_child_nodes(List<ChildNode> *r_child_nodes) override;
 
 	bool has_transition(const StringName &p_from, const StringName &p_to) const;
+	bool has_local_transition(const StringName &p_from, const StringName &p_to) const;
 	int find_transition(const StringName &p_from, const StringName &p_to) const;
 	void add_transition(const StringName &p_from, const StringName &p_to, const Ref<AnimationNodeStateMachineTransition> &p_transition);
 	Ref<AnimationNodeStateMachineTransition> get_transition(int p_transition) const;
 	StringName get_transition_from(int p_transition) const;
 	StringName get_transition_to(int p_transition) const;
 	int get_transition_count() const;
-	void remove_transition_by_index(int p_transition);
+	void remove_transition_by_index(const int p_transition);
 	void remove_transition(const StringName &p_from, const StringName &p_to);
 
-	void set_start_node(const StringName &p_node);
-	String get_start_node() const;
+	bool can_edit_node(const StringName &p_name) const;
 
-	void set_end_node(const StringName &p_node);
-	String get_end_node() const;
+	Ref<AnimationNodeStateMachine> get_prev_state_machine() const;
 
 	void set_graph_offset(const Vector2 &p_offset);
 	Vector2 get_graph_offset() const;

scene/animation/animation_tree.h

@@ -37,6 +37,8 @@
 #include "scene/resources/animation.h"
 
 class AnimationNodeBlendTree;
+class AnimationNodeStartState;
+class AnimationNodeEndState;
 class AnimationPlayer;
 class AnimationTree;
 
@@ -164,6 +166,14 @@ public:
 	AnimationRootNode() {}
 };
 
+class AnimationNodeStartState : public AnimationRootNode {
+	GDCLASS(AnimationNodeStartState, AnimationRootNode);
+};
+
+class AnimationNodeEndState : public AnimationRootNode {
+	GDCLASS(AnimationNodeEndState, AnimationRootNode);
+};
+
 class AnimationTree : public Node {
 	GDCLASS(AnimationTree, Node);