add docs for 3d rotation converter app

doc/source/app_3d-rotation-converter.rst

@@ -0,0 +1,30 @@
+.. _app_3d_rotation-converter:
+
+====================================================
+Application: 3d-rotation-converter
+====================================================
+
+`3d-rotation-converter` is a GUI application to help visualizing relative 
+3D poses (the mathematical group SO(3)) and to convert between different 
+common parameterizations of rotations. Mathematical details on SO(3) 
+parameterizations and transformations between them can be found in :cite:`besl1992method`.
+For the C++ API for SO(3) and SE(3) in MRPT, see the `point and pose classes <group_poses_grp.html>`_
+which belong to the library `mrpt-poses <group_mrpt_poses_grp.html>`_.
+
+Launch the application with:
+
+.. code-block:: bash
+
+   3d-rotation-converter
+
+.. note::
+   An online version of this 3D rotation calculator is available `here <https://mrpt.github.io/webapp-demos/3d-rotation-converter.html>`_
+   and runs directly on the browser (desktop or mobile device).
+
+The following video tutorial summarizes its usage:
+
+.. raw:: html
+
+    <div style="position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; height: auto;">
+        <iframe src="https://www.youtube.com/embed/YOe9Gz26DJg" frameborder="0" allowfullscreen style="position: absolute; top: 0; left: 0; width: 100%; height: 100%;"></iframe>
+    </div>

doc/source/applications.rst

@@ -11,6 +11,7 @@ also provides many ready-to-use applications:
   :maxdepth: 1
 
   app_2d-slam-demo.rst
+  app_3d-rotation-converter.rst
   app_camera-calib.rst
   page_app_carmen2rawlog.rst
   page_app_carmen2rawlog.rst