fix links

docs/modules/tutorials/pages/beginner/hello_node.adoc

@@ -369,7 +369,7 @@ To roll an object 180° around the z axis:
 thing.rotate( 0f , 0f , 180*FastMath.DEG_TO_RAD );
 ----
 
-Tip: If your game idea calls for a serious amount of rotations, it is worth looking into xref:ROOT:jme3/quaternion.adoc[quaternions], a data structure that can combine and store rotations efficiently.
+Tip: If your game idea calls for a serious amount of rotations, it is worth looking into xref:core:math/quaternion.adoc[quaternions], a data structure that can combine and store rotations efficiently.
 
 [source,java]
 ----

docs/modules/tutorials/pages/concepts/math.adoc

@@ -2,7 +2,7 @@
 :revnumber: 2.1
 :revdate: 2020/07/24
 
-It's a fact of life, math is hard. Unfortunately, 3D graphics require a fair bit of knowledge about the subject. Fortunately, jME is able to hide the majority of the details away from the user. Vectors are the fundamental type in the 3D environment, and it is used extensively. Matrices are also a basic necessity of 3D for representing linear systems. xref:ROOT:jme3/quaternion.adoc[Quaternions] are perhaps the most powerful and complicated of the basic types and are used for rotation in jME.
+It's a fact of life, math is hard. Unfortunately, 3D graphics require a fair bit of knowledge about the subject. Fortunately, jME is able to hide the majority of the details away from the user. Vectors are the fundamental type in the 3D environment, and it is used extensively. Matrices are also a basic necessity of 3D for representing linear systems. xref:xref:core:math/quaternion.adoc[Quaternions] are perhaps the most powerful and complicated of the basic types and are used for rotation in jME.
 
 I'll discuss how these are used in the system for the core functionality. Including Transforming, Visibility Determination, Collision Detection, and the Coordinate System. Note, that these are low level details. Further chapters will discuss how to use these various systems from a high level perspective.
 
@@ -340,7 +340,7 @@ These basic operations allow us to convert various rotation representations to Q
 
 === Angle Axis
 
-You might wish to represent your rotations as Angle Axis pairs. That is, you define a axis of rotation and the angle with which to xref:concepts/rotate.adoc[rotate] about this axis. xref:ROOT:jme3/quaternion.adoc[Quaternions] defines a method `fromAngleAxis` (and `fromAngleNormalAxis`) to create a Quaternion from this pair. This is acutally used quite a bit in jME demos to continually rotate objects. You can also obtain a Angle Axis rotation from an existing Quaternion using `toAngleAxis`.
+You might wish to represent your rotations as Angle Axis pairs. That is, you define a axis of rotation and the angle with which to xref:concepts/rotate.adoc[rotate] about this axis. xref:core:math/quaternion.adoc[Quaternions] defines a method `fromAngleAxis` (and `fromAngleNormalAxis`) to create a Quaternion from this pair. This is acutally used quite a bit in jME demos to continually rotate objects. You can also obtain a Angle Axis rotation from an existing Quaternion using `toAngleAxis`.
 
 
 ==== Example - Rotate a Spatial Using fromAngleAxis

docs/modules/tutorials/pages/concepts/rotate.adoc

@@ -6,7 +6,7 @@ _Bad news: 3D rotation is done using matrix calculus. +
 Good news: If you do not understand calculus, there are two simple rules how you get it right._
 
 
-*3D rotation* is a crazy mathematical operation where you need to multiply all vertices in your object by four floating point numbers; the multiplication is referred to as concatenation, the array of four numbers {x,y,z,w} is referred to as xref:ROOT:jme3/quaternion.adoc[quaternion]. Don't worry, the 3D engine does the tough work for you. All you need to know is:
+*3D rotation* is a crazy mathematical operation where you need to multiply all vertices in your object by four floating point numbers; the multiplication is referred to as concatenation, the array of four numbers {x,y,z,w} is referred to as xref:core:math/quaternion.adoc[quaternions]. Don't worry, the 3D engine does the tough work for you. All you need to know is:
 
 *The Quaternion* is an object capable of deep-freezing and storing a rotation that you can apply to a 3D object.
 
@@ -184,4 +184,4 @@ You can do all transformations in individual steps (and then update the objects
 
 *  com.jme3.math.Transform, interpolateTransforms() – interpolate a step between two transformations
 **  link:{link-javadoc}/com/jme3/math/Transform.html[com.jme.math.Transform]
-*  In case you missed it, see also xref:ROOT:jme3/quaternion.adoc[quaternion].
+*  In case you missed it, see also xref:core:math/quaternion.adoc[quaternion].