fix link trees.adoc

docs/modules/ROOT/pages/jme3/contributions/vegetationsystem/trees.adoc

@@ -1,10 +1,6 @@
 = The Tree System
-:author: 
-:revnumber: 
-:revdate: 2016/03/17 20:48
-:relfileprefix: ../../../
-:imagesdir: ../../..
-ifdef::env-github,env-browser[:outfilesuffix: .adoc]
+:revnumber: 2.0
+:revdate: 2020/07/15
 
 
 Here you will learn how to use the tree system.
@@ -32,13 +28,13 @@ The basic procedure is this:
 
 == PhysicsTest.java
 
-There's another file in the demo project called PhysicsTest.java. In that file you can see how collision-shapes are added to the trees. 
+There's another file in the demo project called PhysicsTest.java. In that file you can see how collision-shapes are added to the trees.
 
 When you create a tree-layer through *treeLoader.createTreeLayer(Spatial spat, boolean usePhysics)*, you supply the model and a boolean whether or not to use physics. If you want to enable collision physics, look in that file how it's done.
 
 There are some general principles:
 
-1) In order to enable collision physics _at all_, you first need to set up a physics space. There's a great tutorial available in the tutorials section of the jME wiki: <<jme3/beginner/hello_physics#,jme3:beginner:hello_physics>>.
+1) In order to enable collision physics _at all_, you first need to set up a physics space. There's a great tutorial available in the tutorials section of the jME wiki: xref:tutorials:beginner/hello_physics.adoc[jme3:beginner:hello_physics].
 
 2) If you want to enable physics with the forester, you need to provide the physics space to the Forester object. This is shown in the PhysicsTest.java file.
 
@@ -69,6 +65,6 @@ Tree data is stored in TreeDataLists, which are basically arraylists.
 
 *Using tree data*
 
-In the SimpleTreeTest.java is an example of how to set up a treeloader to use density maps to generate tree-data through the *MapGrid* data-provider. You do not have to worry about this stuff if you use density maps. 
+In the SimpleTreeTest.java is an example of how to set up a treeloader to use density maps to generate tree-data through the *MapGrid* data-provider. You do not have to worry about this stuff if you use density maps.
 
 There will be info here on how to use the alternative *DataGrid* data-provider later.