New and improved IK in Skeleton2D

core/math/transform_2d.cpp

@@ -158,6 +158,13 @@ bool Transform2D::is_equal_approx(const Transform2D &p_transform) const {
 	return elements[0].is_equal_approx(p_transform.elements[0]) && elements[1].is_equal_approx(p_transform.elements[1]) && elements[2].is_equal_approx(p_transform.elements[2]);
 }
 
+Transform2D Transform2D::looking_at(const Vector2 p_target) const {
+	Transform2D return_trans = Transform2D(get_rotation(), get_origin());
+	Vector2 target_position = affine_inverse().xform(p_target);
+	return_trans.set_rotation(return_trans.get_rotation() + (target_position * get_scale()).angle());
+	return return_trans;
+}
+
 bool Transform2D::operator==(const Transform2D &p_transform) const {
 	for (int i = 0; i < 3; i++) {
 		if (elements[i] != p_transform.elements[i]) {

core/math/transform_2d.h

@@ -100,6 +100,8 @@ struct Transform2D {
 	Transform2D orthonormalized() const;
 	bool is_equal_approx(const Transform2D &p_transform) const;
 
+	Transform2D looking_at(const Vector2 p_target) const;
+
 	bool operator==(const Transform2D &p_transform) const;
 	bool operator!=(const Transform2D &p_transform) const;
 

core/variant/variant_call.cpp

@@ -1361,6 +1361,8 @@ static void _register_variant_builtin_methods() {
 	bind_method(Transform2D, basis_xform_inv, sarray("v"), varray());
 	bind_method(Transform2D, interpolate_with, sarray("xform", "weight"), varray());
 	bind_method(Transform2D, is_equal_approx, sarray("xform"), varray());
+	bind_method(Transform2D, set_rotation, sarray("rotation"), varray());
+	bind_method(Transform2D, looking_at, sarray("target"), varray(Transform2D()));
 
 	/* Basis */
 

doc/classes/Bone2D.xml

@@ -19,25 +19,72 @@
 				Stores the node's current transforms in [member rest].
 			</description>
 		</method>
+		<method name="get_autocalculate_length_and_angle" qualifiers="const">
+			<return type="bool">
+			</return>
+			<description>
+				Returns whether this [code]Bone2D[/code] node is going to autocalculate its length and bone angle using its first [code]Bone2D[/code] child node, if one exists. If there are no [code]Bone2D[/code] children, then it cannot autocalculate these values and will print a warning.
+			</description>
+		</method>
+		<method name="get_bone_angle" qualifiers="const">
+			<return type="float">
+			</return>
+			<description>
+				Returns the angle of the bone in the [code]Bone2D[/code] node.
+				[b]Note:[/b] This is different from the [code]Bone2D[/code]'s rotation. The bone angle is the rotation of the bone shown by the [code]Bone2D[/code] gizmo, and because [code]Bone2D[/code] bones are based on positions, this can vary from the actual rotation of the [code]Bone2D[/code] node.
+			</description>
+		</method>
 		<method name="get_index_in_skeleton" qualifiers="const">
 			<return type="int">
 			</return>
 			<description>
 				Returns the node's index as part of the entire skeleton. See [Skeleton2D].
 			</description>
 		</method>
+		<method name="get_length" qualifiers="const">
+			<return type="float">
+			</return>
+			<description>
+				Returns the length of the bone in the [code]Bone2D[/code] node.
+			</description>
+		</method>
 		<method name="get_skeleton_rest" qualifiers="const">
 			<return type="Transform2D">
 			</return>
 			<description>
 				Returns the node's [member rest] [code]Transform2D[/code] if it doesn't have a parent, or its rest pose relative to its parent.
 			</description>
 		</method>
+		<method name="set_autocalculate_length_and_angle">
+			<return type="void">
+			</return>
+			<argument index="0" name="auto_calculate" type="bool">
+			</argument>
+			<description>
+				When set to [code]true[/code], the [code]Bone2D[/code] node will attempt to automatically calculate the bone angle and length using the first child [code]Bone2D[/code] node, if one exists. If none exist, the [code]Bone2D[/code] cannot automatically calculate these values and will print a warning.
+			</description>
+		</method>
+		<method name="set_bone_angle">
+			<return type="void">
+			</return>
+			<argument index="0" name="angle" type="float">
+			</argument>
+			<description>
+				Sets the bone angle for the [code]Bone2D[/code] node. This is typically set to the rotation from the [code]Bone2D[/code] node to a child [code]Bone2D[/code] node.
+				[b]Note:[/b] This is different from the [code]Bone2D[/code]'s rotation. The bone angle is the rotation of the bone shown by the [code]Bone2D[/code] gizmo, and because [code]Bone2D[/code] bones are based on positions, this can vary from the actual rotation of the [code]Bone2D[/code] node.
+			</description>
+		</method>
+		<method name="set_length">
+			<return type="void">
+			</return>
+			<argument index="0" name="length" type="float">
+			</argument>
+			<description>
+				Sets the length of the bone in the [code]Bone2D[/code] node.
+			</description>
+		</method>
 	</methods>
 	<members>
-		<member name="default_length" type="float" setter="set_default_length" getter="get_default_length" default="16.0">
-			Length of the bone's representation drawn in the editor's viewport in pixels.
-		</member>
 		<member name="rest" type="Transform2D" setter="set_rest" getter="get_rest" default="Transform2D( 0, 0, 0, 0, 0, 0 )">
 			Rest transform of the bone. You can reset the node's transforms to this value using [method apply_rest].
 		</member>

doc/classes/Node.xml

@@ -969,6 +969,12 @@
 		<constant name="NOTIFICATION_POST_ENTER_TREE" value="27">
 			Notification received when the node is ready, just before [constant NOTIFICATION_READY] is received. Unlike the latter, it's sent every time the node enters tree, instead of only once.
 		</constant>
+		<constant name="NOTIFICATION_EDITOR_PRE_SAVE" value="9001">
+			Notification received right before the scene with the node is saved in the editor. This notification is only sent in the Godot editor and will not occur in exported projects.
+		</constant>
+		<constant name="NOTIFICATION_EDITOR_POST_SAVE" value="9002">
+			Notification received right after the scene with the node is saved in the editor. This notification is only sent in the Godot editor and will not occur in exported projects.
+		</constant>
 		<constant name="NOTIFICATION_WM_MOUSE_ENTER" value="1002">
 			Notification received from the OS when the mouse enters the game window.
 			Implemented on desktop and web platforms.

doc/classes/PhysicalBone2D.xml

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="PhysicalBone2D" inherits="RigidBody2D" version="4.0">
+	<brief_description>
+		A 2D node that can be used for physically aware bones in 2D.
+	</brief_description>
+	<description>
+		The [code]PhysicalBone2D[/code] node is a [RigidBody2D]-based node that can be used to make [Bone2D] nodes in a [Skeleton2D] react to physics. This node is very similar to the [PhysicalBone3D] node, just for 2D instead of 3D.
+		[b]Note:[/b] To have the Bone2D nodes visually follow the [code]PhysicalBone2D[/code] node, use a [SkeletonModification2DPhysicalBones] modification on the [Skeleton2D] node with the [Bone2D] nodes.
+		[b]Note:[/b] The PhysicalBone2D node does not automatically create a [Joint2D] node to keep [code]PhysicalBone2D[/code] nodes together. You will need to create these manually. For most cases, you want to use a [PinJoint2D] node. The [code]PhysicalBone2D[/code] node can automatically configure the [Joint2D] node once it's been created as a child node.
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+		<method name="get_joint" qualifiers="const">
+			<return type="Joint2D">
+			</return>
+			<description>
+				Returns the first [Joint2D] child node, if one exists. This is mainly a helper function to make it easier to get the [Joint2D] that the [code]PhysicalBone2D[/code] is autoconfiguring.
+			</description>
+		</method>
+		<method name="is_simulating_physics" qualifiers="const">
+			<return type="bool">
+			</return>
+			<description>
+				Returns a boolean that indicates whether the [code]PhysicalBone2D[/code] node is running and simulating using the Godot 2D physics engine. When [code]true[/code], the PhysicalBone2D node is using physics.
+			</description>
+		</method>
+	</methods>
+	<members>
+		<member name="auto_configure_joint" type="bool" setter="set_auto_configure_joint" getter="get_auto_configure_joint" default="true">
+			If [code]true[/code], the [code]PhysicalBone2D[/code] node will automatically configure the first [Joint2D] child node. The automatic configuration is limited to setting up the node properties and positioning the [Joint2D].
+		</member>
+		<member name="bone2d_index" type="int" setter="set_bone2d_index" getter="get_bone2d_index" default="-1">
+			The index of the [Bone2D] node that this [code]PhysicalBone2D[/code] node is supposed to be simulating.
+		</member>
+		<member name="bone2d_nodepath" type="NodePath" setter="set_bone2d_nodepath" getter="get_bone2d_nodepath" default="NodePath(&quot;&quot;)">
+			The [NodePath] to the [Bone2D] node that this [code]PhysicalBone2D[/code] node is supposed to be simulating.
+		</member>
+		<member name="follow_bone_when_simulating" type="bool" setter="set_follow_bone_when_simulating" getter="get_follow_bone_when_simulating" default="false">
+			If [code]true[/code], the [code]PhysicalBone2D[/code] will keep the transform of the bone it is bound to when simulating physics.
+		</member>
+		<member name="simulate_physics" type="bool" setter="set_simulate_physics" getter="get_simulate_physics" default="false">
+			If [code]true[/code], the [code]PhysicalBone2D[/code] will start simulating using physics. If [code]false[/code], the [code]PhysicalBone2D[/code] will follow the transform of the [Bone2D] node.
+			[b]Note:[/b] To have the Bone2D nodes visually follow the [code]PhysicalBone2D[/code] node, use a [SkeletonModification2DPhysicalBones] modification on the [Skeleton2D] node with the [Bone2D] nodes.
+		</member>
+	</members>
+	<constants>
+	</constants>
+</class>

doc/classes/Skeleton2D.xml

@@ -10,6 +10,17 @@
 		<link title="2D skeletons">https://docs.godotengine.org/en/latest/tutorials/animation/2d_skeletons.html</link>
 	</tutorials>
 	<methods>
+		<method name="execute_modifications">
+			<return type="void">
+			</return>
+			<argument index="0" name="execution_mode" type="float">
+			</argument>
+			<argument index="1" name="execution_mode" type="int">
+			</argument>
+			<description>
+				Executes all the modifications on the [SkeletonModificationStack2D], if the Skeleton3D has one assigned.
+			</description>
+		</method>
 		<method name="get_bone">
 			<return type="Bone2D">
 			</return>
@@ -26,17 +37,60 @@
 				Returns the number of [Bone2D] nodes in the node hierarchy parented by Skeleton2D.
 			</description>
 		</method>
+		<method name="get_bone_local_pose_override">
+			<return type="Transform2D">
+			</return>
+			<argument index="0" name="bone_idx" type="int">
+			</argument>
+			<description>
+				Returns the local pose override transform for [code]bone_idx[/code].
+			</description>
+		</method>
+		<method name="get_modification_stack" qualifiers="const">
+			<return type="SkeletonModificationStack2D">
+			</return>
+			<description>
+				Returns the [SkeletonModificationStack2D] attached to this skeleton, if one exists.
+			</description>
+		</method>
 		<method name="get_skeleton" qualifiers="const">
 			<return type="RID">
 			</return>
 			<description>
 				Returns the [RID] of a Skeleton2D instance.
 			</description>
 		</method>
+		<method name="set_bone_local_pose_override">
+			<return type="void">
+			</return>
+			<argument index="0" name="bone_idx" type="int">
+			</argument>
+			<argument index="1" name="override_pose" type="Transform2D">
+			</argument>
+			<argument index="2" name="strength" type="float">
+			</argument>
+			<argument index="3" name="persistent" type="bool">
+			</argument>
+			<description>
+				Sets the local pose transform, [code]pose[/code], for the bone at [code]bone_idx[/code].
+				[code]amount[/code] is the interpolation strengh that will be used when applying the pose, and [code]persistent[/code] determines if the applied pose will remain.
+				[b]Note[/b]: The pose transform needs to be a local transform relative to the [Bone2D] node at [code]bone_idx[/code]!
+			</description>
+		</method>
+		<method name="set_modification_stack">
+			<return type="void">
+			</return>
+			<argument index="0" name="modification_stack" type="SkeletonModificationStack2D">
+			</argument>
+			<description>
+				Sets the [SkeletonModificationStack2D] attached to this skeleton.
+			</description>
+		</method>
 	</methods>
 	<signals>
 		<signal name="bone_setup_changed">
 			<description>
+				Emitted when the [Bone2D] setup attached to this skeletons changes. This is primarily used internally within the skeleton.
 			</description>
 		</signal>
 	</signals>

doc/classes/SkeletonModification2D.xml

@@ -0,0 +1,103 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="SkeletonModification2D" inherits="Resource" version="4.0">
+	<brief_description>
+		A resource that operates on [Bone2D] nodes in a [Skeleton2D].
+	</brief_description>
+	<description>
+		This resource provides an interface that can be expanded so code that operates on [Bone2D] nodes in a [Skeleton2D] can be mixed and matched together to create complex interactions.
+		This is used to provide Godot with a flexible and powerful Inverse Kinematics solution that can be adapted for many different uses.
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+		<method name="clamp_angle">
+			<return type="float">
+			</return>
+			<argument index="0" name="angle" type="float">
+			</argument>
+			<argument index="1" name="min" type="float">
+			</argument>
+			<argument index="2" name="max" type="float">
+			</argument>
+			<argument index="3" name="invert" type="bool">
+			</argument>
+			<description>
+				Takes a angle and clamps it so it is within the passed-in [code]min[/code] and [code]max[/code] range. [code]invert[/code] will inversely clamp the angle, clamping it to the range outside of the given bounds.
+			</description>
+		</method>
+		<method name="draw_editor_gizmo" qualifiers="virtual">
+			<return type="void">
+			</return>
+			<description>
+				Used for drawing [b]editor-only[/b] modification gizmos. This function will only be called in the Godot editor and can be overriden to draw custom gizmos.
+				[b]Note:[/b] You will need to use the Skeleton2D from [method SkeletonModificationStack2D.get_skeleton] and it's draw functions, as the [SkeletonModification2D] resource cannot draw on its own.
+			</description>
+		</method>
+		<method name="execute" qualifiers="virtual">
+			<return type="void">
+			</return>
+			<argument index="0" name="delta" type="float">
+			</argument>
+			<description>
+				Executes the given modification. This is where the modification performs whatever function it is designed to do.
+			</description>
+		</method>
+		<method name="get_editor_draw_gizmo" qualifiers="const">
+			<return type="bool">
+			</return>
+			<description>
+				Returns whether this modification will call [method draw_editor_gizmo] in the Godot editor to draw modification-specific gizmos.
+			</description>
+		</method>
+		<method name="get_is_setup" qualifiers="const">
+			<return type="bool">
+			</return>
+			<description>
+				Returns whether this modification has been successfully setup or not.
+			</description>
+		</method>
+		<method name="get_modification_stack">
+			<return type="SkeletonModificationStack2D">
+			</return>
+			<description>
+				Returns the [SkeletonModificationStack2D] that this modification is bound to. Through the modification stack, you can access the Skeleton3D the modification is operating on.
+			</description>
+		</method>
+		<method name="set_editor_draw_gizmo">
+			<return type="void">
+			</return>
+			<argument index="0" name="draw_gizmo" type="bool">
+			</argument>
+			<description>
+				Sets whether this modification will call [method draw_editor_gizmo] in the Godot editor to draw modification-specific gizmos.
+			</description>
+		</method>
+		<method name="set_is_setup">
+			<return type="void">
+			</return>
+			<argument index="0" name="is_setup" type="bool">
+			</argument>
+			<description>
+				Manually allows you to set the setup state of the modification. This function should only rarely be used, as the [SkeletonModificationStack2D] the modification is bound to should handle setting the modification up.
+			</description>
+		</method>
+		<method name="setup_modification" qualifiers="virtual">
+			<return type="void">
+			</return>
+			<argument index="0" name="modification_stack" type="SkeletonModificationStack2D">
+			</argument>
+			<description>
+			</description>
+		</method>
+	</methods>
+	<members>
+		<member name="enabled" type="bool" setter="set_enabled" getter="get_enabled" default="true">
+			If [code]true[/code], the modification's [method execute] function will be called by the [SkeletonModificationStack2D].
+		</member>
+		<member name="execution_mode" type="int" setter="set_execution_mode" getter="get_execution_mode" default="0">
+			The execution mode for the modification. This tells the modification stack when to execute the modification. Some modifications have settings that are only availible in certain execution modes.
+		</member>
+	</members>
+	<constants>
+	</constants>
+</class>