Add AnimatableBody inherited from StaticBody for moving platforms

Instead of having a physics node named Static that can be either Static
or Kinematic, AnimatableBody is added again as a separate node:
-Inherited from StaticBody to make its usage clearer
-Still separated from CharacterBody to make its usage more focused

Properly implemented constant velocity for kinematic bodies in godot
physics servers (induced velocity without actually moving).

Also updated description for the different physics nodes to make their
usage clearer.

doc/classes/AnimatableBody2D.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="AnimatableBody2D" inherits="StaticBody2D" version="4.0">
+	<brief_description>
+		Physics body for 2D physics which moves only by script or animation. Useful for moving platforms and doors.
+	</brief_description>
+	<description>
+		Animatable body for 2D physics.
+		An animatable body can't be moved by external forces or contacts, but can be moved by script or animation to affect other bodies in its path. It is ideal for implementing moving objects in the environment, such as moving platforms or doors.
+		When the body is moved manually, either from code or from an [AnimationPlayer] (with [member AnimationPlayer.playback_process_mode] set to [code]physics[/code]), the physics will automatically compute an estimate of their linear and angular velocity. This makes them very useful for moving platforms or other AnimationPlayer-controlled objects (like a door, a bridge that opens, etc).
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+	</methods>
+	<members>
+		<member name="sync_to_physics" type="bool" setter="set_sync_to_physics" getter="is_sync_to_physics_enabled" default="false">
+			If [code]true[/code], the body's movement will be synchronized to the physics frame. This is useful when animating movement via [AnimationPlayer], for example on moving platforms. Do [b]not[/b] use together with [method PhysicsBody2D.move_and_collide].
+		</member>
+	</members>
+	<constants>
+	</constants>
+</class>

doc/classes/AnimatableBody3D.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="AnimatableBody3D" inherits="StaticBody3D" version="4.0">
+	<brief_description>
+		Physics body for 3D physics which moves only by script or animation. Useful for moving platforms and doors.
+	</brief_description>
+	<description>
+		Animatable body for 3D physics.
+		An animatable body can't be moved by external forces or contacts, but can be moved by script or animation to affect other bodies in its path. It is ideal for implementing moving objects in the environment, such as moving platforms or doors.
+		When the body is moved manually, either from code or from an [AnimationPlayer] (with [member AnimationPlayer.playback_process_mode] set to [code]physics[/code]), the physics will automatically compute an estimate of their linear and angular velocity. This makes them very useful for moving platforms or other AnimationPlayer-controlled objects (like a door, a bridge that opens, etc).
+	</description>
+	<tutorials>
+		<link title="3D Physics Tests Demo">https://godotengine.org/asset-library/asset/675</link>
+		<link title="Third Person Shooter Demo">https://godotengine.org/asset-library/asset/678</link>
+		<link title="3D Voxel Demo">https://godotengine.org/asset-library/asset/676</link>
+	</tutorials>
+	<methods>
+	</methods>
+	<members>
+		<member name="sync_to_physics" type="bool" setter="set_sync_to_physics" getter="is_sync_to_physics_enabled" default="false">
+			If [code]true[/code], the body's movement will be synchronized to the physics frame. This is useful when animating movement via [AnimationPlayer], for example on moving platforms. Do [b]not[/b] use together with [method PhysicsBody3D.move_and_collide].
+		</member>
+	</members>
+	<constants>
+	</constants>
+</class>

doc/classes/CharacterBody2D.xml

@@ -1,12 +1,12 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="CharacterBody2D" inherits="PhysicsBody2D" version="4.0">
 	<brief_description>
-		Character body 2D node.
+		Specialized 2D physics body node for characters moved by script.
 	</brief_description>
 	<description>
-		Character bodies are special types of bodies that are meant to be user-controlled. They are not affected by physics at all; to other types of bodies, such as a rigid body, these are the same as a static body. However, they have two main uses:
-		[b]Kinematic characters:[/b] Character bodies have an API for moving objects with walls and slopes detection ([method move_and_slide] method), in addition to collision detection (also done with [method PhysicsBody3D.move_and_collide]). This makes them really useful to implement characters that move in specific ways and collide with the world, but don't require advanced physics.
-		[b]Kinematic motion:[/b] Character bodies can also be used for kinematic motion (same functionality as [member StaticBody3D.kinematic_motion] when enabled), which allows them to be moved by code and push other bodies on their path.
+		Character bodies are special types of bodies that are meant to be user-controlled. They are not affected by physics at all; to other types of bodies, such as a rigid body, these are the same as a [AnimatableBody2D]. However, they have two main uses:
+		[b]Kinematic characters:[/b] Character bodies have an API for moving objects with walls and slopes detection ([method move_and_slide] method), in addition to collision detection (also done with [method PhysicsBody2D.move_and_collide]). This makes them really useful to implement characters that move in specific ways and collide with the world, but don't require advanced physics.
+		[b]Kinematic motion:[/b] Character bodies can also be used for kinematic motion (same functionality as [AnimatableBody2D]), which allows them to be moved by code and push other bodies on their path.
 	</description>
 	<tutorials>
 		<link title="Kinematic character (2D)">https://docs.godotengine.org/en/latest/tutorials/physics/kinematic_character_2d.html</link>

doc/classes/CharacterBody3D.xml

@@ -1,12 +1,12 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="CharacterBody3D" inherits="PhysicsBody3D" version="4.0">
 	<brief_description>
-		Character body 3D node.
+		Specialized 3D physics body node for characters moved by script.
 	</brief_description>
 	<description>
-		Character bodies are special types of bodies that are meant to be user-controlled. They are not affected by physics at all; to other types of bodies, such as a rigid body, these are the same as a static body. However, they have two main uses:
+		Character bodies are special types of bodies that are meant to be user-controlled. They are not affected by physics at all; to other types of bodies, such as a rigid body, these are the same as a [AnimatableBody3D]. However, they have two main uses:
 		[b]Kinematic characters:[/b] Character bodies have an API for moving objects with walls and slopes detection ([method move_and_slide] method), in addition to collision detection (also done with [method PhysicsBody3D.move_and_collide]). This makes them really useful to implement characters that move in specific ways and collide with the world, but don't require advanced physics.
-		[b]Kinematic motion:[/b] Character bodies can also be used for kinematic motion (same functionality as [member StaticBody3D.kinematic_motion] when enabled), which allows them to be moved by code and push other bodies on their path.
+		[b]Kinematic motion:[/b] Character bodies can also be used for kinematic motion (same functionality as [AnimatableBody3D]), which allows them to be moved by code and push other bodies on their path.
 	</description>
 	<tutorials>
 		<link title="Kinematic character (2D)">https://docs.godotengine.org/en/latest/tutorials/physics/kinematic_character_2d.html</link>

doc/classes/PhysicsServer2D.xml

@@ -913,7 +913,7 @@
 			This area replaces any gravity/damp calculated so far, but keeps calculating the rest of the areas, down to the default one.
 		</constant>
 		<constant name="BODY_MODE_STATIC" value="0" enum="BodyMode">
-			Constant for static bodies. In this mode, a body can be only moved by user code.
+			Constant for static bodies. In this mode, a body can be only moved by user code and doesn't collide with other bodies along its path when moved.
 		</constant>
 		<constant name="BODY_MODE_KINEMATIC" value="1" enum="BodyMode">
 			Constant for kinematic bodies. In this mode, a body can be only moved by user code and collides with other bodies along its path.

doc/classes/PhysicsServer3D.xml

@@ -1262,7 +1262,7 @@
 			This area replaces any gravity/damp calculated so far, but keeps calculating the rest of the areas, down to the default one.
 		</constant>
 		<constant name="BODY_MODE_STATIC" value="0" enum="BodyMode">
-			Constant for static bodies. In this mode, a body can be only moved by user code.
+			Constant for static bodies. In this mode, a body can be only moved by user code and doesn't collide with other bodies along its path when moved.
 		</constant>
 		<constant name="BODY_MODE_KINEMATIC" value="1" enum="BodyMode">
 			Constant for kinematic bodies. In this mode, a body can be only moved by user code and collides with other bodies along its path.

doc/classes/RigidBody2D.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="RigidBody2D" inherits="PhysicsBody2D" version="4.0">
 	<brief_description>
-		A body that is controlled by the 2D physics engine.
+		Physics Body which is moved by 2D physics simulation. Useful for objects that have gravity and can be pushed by other objects.
 	</brief_description>
 	<description>
 		This node implements simulated 2D physics. You do not control a RigidBody2D directly. Instead, you apply forces to it (gravity, impulses, etc.) and the physics simulation calculates the resulting movement based on its mass, friction, and other physical properties.
@@ -131,6 +131,7 @@
 		</member>
 		<member name="mode" type="int" setter="set_mode" getter="get_mode" enum="RigidBody2D.Mode" default="0">
 			The body's mode. See [enum Mode] for possible values.
+			For a body that uses only Static or Kinematic mode, use [StaticBody2D] or [AnimatableBody2D] instead.
 		</member>
 		<member name="physics_material_override" type="PhysicsMaterial" setter="set_physics_material_override" getter="get_physics_material_override">
 			The physics material override for the body.
@@ -199,7 +200,7 @@
 			Locked dynamic body mode. Similar to [constant MODE_DYNAMIC], but the body can not rotate.
 		</constant>
 		<constant name="MODE_KINEMATIC" value="3" enum="Mode">
-			Kinematic body mode. The body behaves like a [StaticBody2D] with [member StaticBody2D.kinematic_motion] enabled, and must be moved by user code.
+			Kinematic body mode. The body behaves like a [AnimatableBody2D], and must be moved by code.
 		</constant>
 		<constant name="CCD_MODE_DISABLED" value="0" enum="CCDMode">
 			Continuous collision detection disabled. This is the fastest way to detect body collisions, but can miss small, fast-moving objects.

doc/classes/RigidBody3D.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="RigidBody3D" inherits="PhysicsBody3D" version="4.0">
 	<brief_description>
-		Physics Body whose position is determined through physics simulation in 3D space.
+		Physics Body which is moved by 3D physics simulation. Useful for objects that have gravity and can be pushed by other objects.
 	</brief_description>
 	<description>
 		This is the node that implements full 3D physics. This means that you do not control a RigidBody3D directly. Instead, you can apply forces to it (gravity, impulses, etc.), and the physics simulation will calculate the resulting movement, collision, bouncing, rotating, etc.
@@ -130,7 +130,8 @@
 			The body's mass.
 		</member>
 		<member name="mode" type="int" setter="set_mode" getter="get_mode" enum="RigidBody3D.Mode" default="0">
-			The body mode. See [enum Mode] for possible values.
+			The body's mode. See [enum Mode] for possible values.
+			For a body that uses only Static or Kinematic mode, use [StaticBody3D] or [AnimatableBody3D] instead.
 		</member>
 		<member name="physics_material_override" type="PhysicsMaterial" setter="set_physics_material_override" getter="get_physics_material_override">
 			The physics material override for the body.
@@ -201,7 +202,7 @@
 			Locked dynamic body mode. Similar to [constant MODE_DYNAMIC], but the body can not rotate.
 		</constant>
 		<constant name="MODE_KINEMATIC" value="3" enum="Mode">
-			Kinematic body mode. The body behaves like a [StaticBody3D] with [member StaticBody3D.kinematic_motion] enabled, and can only move by user code.
+			Kinematic body mode. The body behaves like a [AnimatableBody3D], and can only move by user code.
 		</constant>
 	</constants>
 </class>

doc/classes/StaticBody2D.xml

@@ -1,37 +1,30 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="StaticBody2D" inherits="PhysicsBody2D" version="4.0">
 	<brief_description>
-		Static body for 2D physics.
+		Physics body for 2D physics which is static or moves only by script. Useful for floor and walls.
 	</brief_description>
 	<description>
-		Static body for 2D physics. A static body is a simple body that can't be moved by external forces or contacts. It is ideal for implementing objects in the environment, such as walls or platforms. In contrast to [RigidBody2D], they don't consume any CPU resources as long as they don't move.
-		They however have extra functionalities to move and affect other bodies:
-		[b]Constant velocity:[/b] [member constant_linear_velocity] and [member constant_angular_velocity] can be set for the static body, so even if it doesn't move, it affects other bodies as if it was moving (this is useful for simulating conveyor belts or conveyor wheels).
-		[b]Transform change:[/b] Static bodies can be also moved by code. Unless [member kinematic_motion] is enabled, they are just teleported in this case and don't affect other bodies on their path.
-		[b]Kinematic motion:[/b] Static bodies can have [member kinematic_motion] enabled to make them kinematic bodies that can be moved by code and push other bodies on their path.
+		Static body for 2D physics.
+		A static body is a simple body that can't be moved by external forces or contacts. It is ideal for implementing objects in the environment, such as walls or platforms. In contrast to [RigidBody2D], it doesn't consume any CPU resources as long as they don't move.
+		They have extra functionalities to move and affect other bodies:
+		[b]Static transform change:[/b] Static bodies can be moved by animation or script. In this case, they are just teleported and don't affect other bodies on their path.
+		[b]Constant velocity:[/b] When [member constant_linear_velocity] or [member constant_angular_velocity] is set, static bodies don't move themselves but affect touching bodies as if they were moving. This is useful for simulating conveyor belts or conveyor wheels.
 	</description>
 	<tutorials>
 	</tutorials>
 	<methods>
 	</methods>
 	<members>
 		<member name="constant_angular_velocity" type="float" setter="set_constant_angular_velocity" getter="get_constant_angular_velocity" default="0.0">
-			The body's constant angular velocity. This does not rotate the body (unless [member kinematic_motion] is enabled), but affects other bodies that touch it, as if it were rotating.
+			The body's constant angular velocity. This does not rotate the body, but affects touching bodies, as if it were rotating.
 		</member>
 		<member name="constant_linear_velocity" type="Vector2" setter="set_constant_linear_velocity" getter="get_constant_linear_velocity" default="Vector2(0, 0)">
-			The body's constant linear velocity. This does not move the body (unless [member kinematic_motion] is enabled), but affects other bodies that touch it, as if it were moving.
-		</member>
-		<member name="kinematic_motion" type="bool" setter="set_kinematic_motion_enabled" getter="is_kinematic_motion_enabled" default="false">
-			If [code]true[/code], the body will act the same as a [RigidBody2D] in [constant RigidBody2D.MODE_KINEMATIC] mode.
-			When the body is moved manually, either from code or from an [AnimationPlayer] (with [member AnimationPlayer.playback_process_mode] set to [code]physics[/code]), the physics will automatically compute an estimate of their linear and angular velocity. This makes them very useful for moving platforms or other AnimationPlayer-controlled objects (like a door, a bridge that opens, etc).
+			The body's constant linear velocity. This does not move the body, but affects touching bodies, as if it were moving.
 		</member>
 		<member name="physics_material_override" type="PhysicsMaterial" setter="set_physics_material_override" getter="get_physics_material_override">
 			The physics material override for the body.
 			If a material is assigned to this property, it will be used instead of any other physics material, such as an inherited one.
 		</member>
-		<member name="sync_to_physics" type="bool" setter="set_sync_to_physics" getter="is_sync_to_physics_enabled" default="false">
-			If [code]true[/code] and [member kinematic_motion] is enabled, the body's movement will be synchronized to the physics frame. This is useful when animating movement via [AnimationPlayer], for example on moving platforms. Do [b]not[/b] use together with [method PhysicsBody2D.move_and_collide].
-		</member>
 	</members>
 	<constants>
 	</constants>