[Unity plugin] Reference the tutorial in the Unity plugin docs

doc/unity.rst

@@ -10,6 +10,9 @@ runtime to use the MuJoCo physics engine.  Users can import MJCF files and edit
 relies on Unity for most aspects -- assets, game logic, simulation time -- but uses MuJoCo to determine how objects
 move, giving the designer access to MuJoCo's full API.
 
+An example project using MuJoCo's Unity plugin in a set of introductory tutorials is available at
+https://github.com/Balint-H/mj-unity-tutorial.
+
 .. _UInstallation:
 
 Installation instructions
@@ -18,7 +21,10 @@ Installation instructions
 The plug-in directory (available at https://github.com/google-deepmind/mujoco/tree/main/unity) includes a
 ``package.json`` file.  Unity's package manager recognizes this file and will import the plug-in's C# codebase to your
 project. In addition, Unity also needs the native MuJoCo library, which can be found in the specific platform archive at
-https://github.com/google-deepmind/mujoco/releases.
+https://github.com/google-deepmind/mujoco/releases. If you wish to simply use the plug-in and not develop it, you should
+use one of the version-specific stable commits of the repository, identified by git tags. Check out the relevant version
+of the cloned repository with git (``git checkout 3.X.Y`` where X and Y specify the engine version). Simply using the
+``main`` branch of the repository may not be compatible with the most recent release binary of MuJoCo.
 
 On Unity version 2020.2 and later, the Package Manager will look for the native library file and copy it to the package
 directory when the package is imported. Alternatively, you can manually copy the native library to the package directory
@@ -145,10 +151,6 @@ effects:
   material assets for geom RGBA specification.
 - It allows the importer to handle :ref:`\<include\> <include>` elements without replicating MuJoCo’s file-system
   workflow.
-- The current version of MuJoCo generates MJCF files with explicit :ref:`\<inertial\> <body-inertial>` elements, even when
-  the original model uses geoms for implicit definition of the body inertia.  If you plan to change geom properties of
-  an imported model, remove these auto-generated ``MjInertial`` components manually.  We plan to address this in a
-  future release of MuJoCo.
 
 In Unity, there is no equivalent to MJCF’s “cascading” :ref:`\<default\> <default>` clauses.  Therefore, components in
 Unity reflect the corresponding elements’ state after applying all the relevant default classes, and the class structure
@@ -177,9 +179,10 @@ Scene recreation maintains continuity of physics and state in the following way:
    persisted.
 4. The MuJoCo state (for the joints that persisted) is set from the cache, and Unity transforms are synchronized.
 
-Because the MuJoCo library doesn’t (yet) expose an API for scene editing, adding and removing MuJoCo components causes
-complete scene recreation.  This can be expensive for large models or if it happens frequently.  We expect this
-performance limitation to be lifted in future versions of MuJoCo.
+MuJoCo has functionality for dynamic scene editing (through :ref:`mjSpec`), however, this is not yet
+supported in the Unity plugin. Therefore, adding and removing MuJoCo components causes complete scene recreation.  This
+can be expensive for large models or if it happens frequently.  We intend to lift this performance limitation to be in a
+future versions of the plugin.
 
 Global Settings
 _______________
@@ -323,6 +326,20 @@ The plug-in allows using arbitrary Unity meshes for MuJoCo collision.  At model
 <http://www.qhull.org/>`__ to create a convex hull of the mesh, and uses that for collisions.  Currently the computed
 convex hull is not visible in Unity, but we intend to expose it in future versions.
 
+Height fields
+_____________
+
+MuJoCo hfields are represented in Unity through terrain gameobjects. This allows the use of the terrain editing tools
+available in Unity to generate shapes for collisions with MuJoCo. When selecting hfield type in the Unity geom
+component, the right click context menu provides utility to add the corresponding Unity terrain to the scene. The data
+from the terrain is dynamically kept in sync with the simulation.
+
+MuJoCo plugins
+______________
+
+The current version of the Unity package does not support loading MJCF scenes that use :ref:`MuJoCo plugins<exPlugin>` such as
+`elasticity <https://github.com/google-deepmind/mujoco/tree/main/plugin/elasticity#readme>`__ . Adding basic functionality to do this will be part of an upcoming release.
+
 Interaction with External Processes
 ___________________________________