Add two new attributes to weld constraints:

- `anchor` determines the point of wrench application, in the frame of body2.
- `tfratio` scales applied torques relative to applied forces.
- Add visualisation of both anchor points to both weld and connect constraints.
- Add a test model showing how the new weld parameters behave.

PiperOrigin-RevId: 469228149
Change-Id: I836b0791f10fb624607a12ef3c687da991c21789

doc/changelog.rst

@@ -15,13 +15,8 @@ General
 - Added :ref:`adhesion actuators<adhesion>` mimicking vacuum grippers and adhesive biomechanical appendages.
 - Added related `example model <https://github.com/deepmind/mujoco/tree/main/model/adhesion>`_ and video:
 - Added :ref:`mj_jacSubtreeCom` for computing the translational Jacobian of the center-of-mass of a subtree.
-- Added :at:`tfratio` and :at:`anchor` attributes to :el:`weld` constraints. :at:`tfratio` sets the torque-to-force
-  ratio exerted by the constraint, :at:`anchor` sets the point at which the weld wrench is applied. See
-  :ref:`weld <equality-weld>` for more details.
-- Added visualisation of anchor points for both :el:`connect` and :el:`weld` constraints (activated by the 'N' key in
-  ``simulate``).
-- Added `example model <https://github.com/deepmind/mujoco/tree/main/test/engine/testdata/weld.xml>`_ showing different
-  uses of new weld attributes.
+- Added moment of inertia computation for concave meshes. This is currently activated by setting the compiler flag
+  :at:`exactmeshinertia` to ``true`` (defaults to ``false``). This default may change in the future.
 - Joint and tendon ``limited`` attribute and actuator ``ctrllimited``, ``forcelimited`` and ``actlimited`` attributes
   now default to ``auto`` rather than ``false``. Limits are automatically set to ``true`` if the corresponding range *is
   defined* and ``false`` otherwise.
@@ -30,8 +25,6 @@ General
     This is a minor breaking change. In models where a range was defined but :at:`limited` was unspecified, the target
     element will now be limited. Explicitly set limited to ``false`` to revert to the previous behavior.
 
-- Added moment of inertia computation for all well-formed meshes. This option is activated by setting the compiler
-  flag :at:`exactmeshinertia` to ``true`` (defaults to ``false``). This default may change in the future.
 - Added parameter :at:`shellinertia` to :at:`geom`, for locating the inferred inertia on the boundary (shell).
   Currently only meshes are supported.
 - For meshes from which volumetric inertia is inferred, raise error if the orientation of mesh faces is not consistent.