Document the RootMotionView class

(cherry picked from commit 6880829a9ae32804652bde48d3c81d3cd8b5683f)

doc/classes/AnimationTree.xml

@@ -7,7 +7,7 @@
 		Note: When linked with an [AnimationPlayer], several properties and methods of the corresponding [AnimationPlayer] will not function as expected. Playback and transitions should be handled using only the [AnimationTree] and its constituent [AnimationNode](s). The [AnimationPlayer] node should be used solely for adding, deleting, and editing animations.
 	</description>
 	<tutorials>
-		<link title="AnimationTree">https://docs.godotengine.org/en/3.3/tutorials/animation/animation_tree.html</link>
+		<link title="Using AnimationTree">https://docs.godotengine.org/en/3.3/tutorials/animation/animation_tree.html</link>
 		<link title="Third Person Shooter Demo">https://godotengine.org/asset-library/asset/678</link>
 	</tutorials>
 	<methods>
@@ -24,7 +24,7 @@
 			<return type="Transform">
 			</return>
 			<description>
-				Retrieve the motion of the [member root_motion_track] as a [Transform] that can be used elsewhere. If [member root_motion_track] is not a path to a track of type [constant Animation.TYPE_TRANSFORM], returns an identity transformation.
+				Retrieve the motion of the [member root_motion_track] as a [Transform] that can be used elsewhere. If [member root_motion_track] is not a path to a track of type [constant Animation.TYPE_TRANSFORM], returns an identity transformation. See also [member root_motion_track] and [RootMotionView].
 			</description>
 		</method>
 		<method name="rename_parameter">
@@ -50,7 +50,7 @@
 		</member>
 		<member name="root_motion_track" type="NodePath" setter="set_root_motion_track" getter="get_root_motion_track" default="NodePath(&quot;&quot;)">
 			The path to the Animation track used for root motion. Paths must be valid scene-tree paths to a node, and must be specified starting from the parent node of the node that will reproduce the animation. To specify a track that controls properties or bones, append its name after the path, separated by [code]":"[/code]. For example, [code]"character/skeleton:ankle"[/code] or [code]"character/mesh:transform/local"[/code].
-			If the track has type [constant Animation.TYPE_TRANSFORM], the transformation will be cancelled visually, and the animation will appear to stay in place.
+			If the track has type [constant Animation.TYPE_TRANSFORM], the transformation will be cancelled visually, and the animation will appear to stay in place. See also [method get_root_motion_transform] and [RootMotionView].
 		</member>
 		<member name="tree_root" type="AnimationNode" setter="set_tree_root" getter="get_tree_root">
 			The root animation node of this [AnimationTree]. See [AnimationNode].

doc/classes/RootMotionView.xml

@@ -1,23 +1,32 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="RootMotionView" inherits="VisualInstance" version="3.4">
 	<brief_description>
+		Editor-only helper for setting up root motion in [AnimationTree].
 	</brief_description>
 	<description>
+		[i]Root motion[/i] refers to an animation technique where a mesh's skeleton is used to give impulse to a character. When working with 3D animations, a popular technique is for animators to use the root skeleton bone to give motion to the rest of the skeleton. This allows animating characters in a way where steps actually match the floor below. It also allows precise interaction with objects during cinematics. See also [AnimationTree].
+		[b]Note:[/b] [RootMotionView] is only visible in the editor. It will be hidden automatically in the running project, and will also be converted to a plain [Node] in the running project. This means a script attached to a [RootMotionView] node [i]must[/i] have [code]extends Node[/code] instead of [code]extends RootMotionView[/code]. Additionally, it must not be a [code]@tool[/code] script.
 	</description>
 	<tutorials>
+		<link title="Using AnimationTree - Root motion">https://docs.godotengine.org/en/latest/tutorials/animation/animation_tree.html#root-motion</link>
 	</tutorials>
 	<methods>
 	</methods>
 	<members>
 		<member name="animation_path" type="NodePath" setter="set_animation_path" getter="get_animation_path">
+			Path to an [AnimationTree] node to use as a basis for root motion.
 		</member>
 		<member name="cell_size" type="float" setter="set_cell_size" getter="get_cell_size">
+			The grid's cell size in 3D units.
 		</member>
 		<member name="color" type="Color" setter="set_color" getter="get_color">
+			The grid's color.
 		</member>
 		<member name="radius" type="float" setter="set_radius" getter="get_radius">
+			The grid's radius in 3D units. The grid's opacity will fade gradually as the distance from the origin increases until this [member radius] is reached.
 		</member>
 		<member name="zero_y" type="bool" setter="set_zero_y" getter="get_zero_y">
+			If [code]true[/code], the grid's points will all be on the same Y coordinate ([i]local[/i] Y = 0). If [code]false[/code], the points' original Y coordinate is preserved.
 		</member>
 	</members>
 	<constants>