Mujoco

-----------------------------

General
^^^^^^^

1. Added ``mjd_transitionFD`` to compute efficient finite difference approximations of the state-transition and
control-transition matrices, :ref:`see here<derivatives>` for more details.
. Added derivatives for the ellipsoid fluid model.
. Added ``ctrl`` attribute to :ref:`keyframes<keyframe>`.
. Added ``clock`` sensor which :ref:`measures time<sensor-clock>`.
. Added visualisation groups to skins.
. Added actuator visualisation for ``free`` and ``ball`` joints and for actuators with ``site`` transmission.
. Added visualisation for actuator activations.
. Added ``<actuator-intvelocity>`` actuator shortcut for "integrated velocity" actuators, documented
:ref:`here <actuator-intvelocity>`.
. Added ``<actuator-damper>`` actuator shortcut for active-damping actuators, documented :ref:`here <actuator-damper>`.
. ``mju_rotVecMat`` and ``mju_rotVecMatT`` now support in-place multiplication.
. ``mjData.ctrl`` values are no longer clamped in-place, remain untouched by the engine.
. Arrays in mjData's buffer now align to 64-byte boundaries rather than 8-byte.
. Added memory poisoning when building with `Address Sanitizer (ASAN) <https://clang.llvm.org/docs/AddressSanitizer.html>`__
and `Memory Sanitizer (MSAN) <https://clang.llvm.org/docs/MemorySanitizer.html>`__. This allows ASAN to
detect reads and writes to regions in ``mjModel.buffer`` and ``mjData.buffer`` that do not lie within an array, and
for MSAN to detect reads from uninitialised fields in ``mjData`` following ``mj_resetData``.
. Added a `slider-crank example model <https://github.com/google-deepmind/mujoco/tree/main/model/slider_crank>`__.

Bug fixes
^^^^^^^^^

15. :ref:`Activation clamping <CActRange>` was not being applied in the :ref:`implicit integrator<geIntegration>`.
. Stricter parsing of orientation specifiers. Before this change, a specification that included both ``quat`` and an
:ref:`alternative specifier<COrientation>` e.g., ``<geom ... quat=".1 .2 .3 .4" euler="10 20 30">``, would lead to
the ``quat`` being ignored and only ``euler`` being used. After this change a parse error will be thrown.
. Stricter parsing of XML attributes. Before this change an erroneous XML snippet like ``<geom size="1/2 3 4">`` would
have been parsed as ``size="1 0 0"`` and no error would have been thrown. Now throws an error.
. Trying to load a ``NaN`` via XML like ``<geom size="1 NaN 4">``, while allowed for debugging purposes, will now print
a warning.
. Fixed null pointer dereference in ``mj_loadModel``.
. Fixed memory leaks when loading an invalid model from MJB.
. Integer overflows are now avoided when computing ``mjModel`` buffer sizes.
. Added missing warning string for ``mjWARN_BADCTRL``.

Packaging
^^^^^^^^^

23. Changed MacOS packaging so that the copy of ``mujoco.framework`` embedded in ``MuJoCo.app`` can be used to build
applications externally.

----------------------------

Open Sourcing
^^^^^^^^^^^^^

1. MuJoCo is now fully open-source software. Newly available top level directories are:

a. ``src/``: All source files. Subdirectories correspond to the modules described in the Programming chapter
:ref:`introduction<inIntro>`:

- ``src/engine/``: Core engine.
- ``src/xml/``: XML parser.
- ``src/user/``: Model compiler.
- ``src/visualize/``: Abstract visualizer.
- ``src/ui/``: UI framework.

b. ``test/``: Tests and corresponding asset files.

c. ``dist/``: Files related to packaging and binary distribution.

. Added `contributor's guide <https://github.com/google-deepmind/mujoco/blob/main/CONTRIBUTING.md>`__ and
`style guide <https://github.com/google-deepmind/mujoco/blob/main/STYLEGUIDE.md>`__.

General
^^^^^^^

3. Added analytic derivatives of smooth (unconstrained) dynamics forces, with respect to velocities:

- Centripetal and Coriolis forces computed by the Recursive Newton-Euler algorithm.
- Damping and fluid-drag passive forces.
- Actuation forces.

. Added ``implicit`` integrator. Using the analytic derivatives above, a new implicit-in-velocity integrator was added.
This integrator lies between the Euler and Runge Kutta integrators in terms of both stability and computational
cost. It is most useful for models which use fluid drag (e.g. for flying or swimming) and for models which use
:ref:`velocity actuators<actuator-velocity>`. For more details, see the :ref:`Numerical Integration<geIntegration>`
section.

. Added :at:`actlimited` and :at:`actrange` attributes to :ref:`general actuators<actuator-general>`, for clamping
actuator internal states (activations). This clamping is useful for integrated-velocity actuators, see the
:ref:`Activation clamping <CActRange>` section for details.

. ``mjData`` fields ``qfrc_unc`` (unconstrained forces) and ``qacc_unc`` (unconstrained accelerations) were renamed
``qfrc_smooth`` and ``qacc_smooth``, respectively. While "unconstrained" is precise, "smooth" is more intelligible
than "unc".

. Public headers have been moved from ``/include`` to ``/include/mujoco/``, in line with the directory layout common in
other open source projects. Developers are encouraged to include MuJoCo public headers in their own codebase via
``include <mujoco/filename.h>``.

. The default shadow resolution specified by the :ref:`shadowsize<visual-quality>` attribute was increased from 1024 to
4096.

. Saved XMLs now use 2-space indents.

Bug fixes
^^^^^^^^^

10. Antialiasing was disabled for segmentation rendering. Before this change, if the :ref:`offsamples<visual-quality>`
attribute was greater than 0 (the default value is 4), pixels that overlapped with multiple geoms would receive
averaged segmentation IDs, leading to incorrect or non-existent IDs. After this change :at:`offsamples` is ignored
during segmentation rendering.

. The value of the enable flag for the experimental multiCCD feature was made sequential with other enable flags.
Sequentiality is assumed in the ``simulate`` UI and elsewhere.

. Fix issue of duplicated meshes when saving models with OBJ meshes using mj_saveLastXML.

-----------------------------

General
^^^^^^^

1. Added an experimental feature: multi-contact convex collision detection, activated by an enable flag. See full
description :ref:`here <option-flag>`.

Bug fixes
^^^^^^^^^

2. GLAD initialization logic on Linux now calls ``dlopen`` to load a GL platform dynamic library if a
``*GetProcAddress`` function is not already present in the process' global symbol table. In particular, processes
that use GLFW to set up a rendering context that are not explicitly linked against ``libGLX.so`` (this applies to the
Python interpreter, for example) will now work correctly rather than fail with a ``gladLoadGL`` error when
``mjr_makeContext`` is called.

. In the Python bindings, named indexers for scalar fields (e.g. the ``ctrl`` field for actuators) now return a NumPy
array of shape ``(1,)`` rather than ``()``. This allows values to be assigned to these fields more straightforwardly.

----------------------------

General
^^^^^^^

1. MuJoCo now uses GLAD to manage OpenGL API access instead of GLEW. On Linux, there is no longer a need to link against
different GL wrangling libraries depending on whether GLX, EGL, or OSMesa is being used. Instead, users can simply
use GLX, EGL, or OSMesa to create a GL context and ``mjr_makeContext`` will detect which one is being used.

. Added visualisation for contact frames. This is useful when writing or modifying collision functions, when the actual
direction of the x and y axes of a contact can be important.

Binary build
^^^^^^^^^^^^

3. The ``_nogl`` dynamic library is no longer provided on Linux and Windows. The switch to GLAD allows us to resolve
OpenGL symbols when ``mjr_makeContext`` is called rather than when the library is loaded. As a result, the MuJoCo
library no longer has an explicit dynamic dependency on OpenGL, and can be used on system where OpenGL is not
present.

Simulate
^^^^^^^^

4. Fixed a bug in simulate where pressing '[' or ']' when a model is not loaded causes a crash.

. Contact frame visualisation was added to the Simulate GUI.

. Renamed "set key", "reset to key" to "save key" and "load key", respectively.

. Changed bindings of F6 and F7 from the not very useful "vertical sync" and "busy wait" to the more useful cycling of
frames and labels.

Bug fixes
^^^^^^^^^

8. ``mj_resetData`` zeroes out the ``solver_nnz`` field.

. Removed a special branch in ``mju_quat2mat`` for unit quaternions. Previously, ``mju_quat2mat`` skipped all
computation if the real part of the quaternion equals 1.0. For very small angles (e.g. when finite differencing), the
cosine can evaluate to exactly 1.0 at double precision while the sine is still nonzero.

-----------------------------

General
^^^^^^^

1. ``simulate`` now supports cycling through cameras (with the ``[`` and ``]`` keys).
. ``mjVIS_STATIC`` toggles all static bodies, not just direct children of the world.

Python bindings
^^^^^^^^^^^^^^^

3. Added a ``free()`` method to ``MjrContext``.
. Enums now support arithmetic and bitwise operations with numbers.

Bug fixes
^^^^^^^^^

5. Fixed rendering bug for planes, introduced in 2.1.2. This broke maze environments in
`dm_control <https://github.com/google-deepmind/dm_control>`__.

-----------------------------

New modules
^^^^^^^^^^^

1. Added new :doc:`Python bindings<python>`, which can be installed via ``pip install mujoco``,
and imported as ``import mujoco``.
. Added new :doc:`Unity plug-in<unity>`.
. Added a new ``introspect`` module, which provides reflection-like capability for MuJoCo's public API, currently
describing functions and enums. While implemented in Python, this module is expected to be generally useful for
automatic code generation targeting multiple languages. (This is not shipped as part of the ``mujoco`` Python
bindings package.)

API changes
^^^^^^^^^^^

4. Moved definition of ``mjtNum`` floating point type into a new header
`mjtnum.h <https://github.com/google-deepmind/mujoco/blob/3577e2cf8bf841475b489aefff52276a39f24d51/include/mjtnum.h>`__.
. Renamed header `mujoco_export.h` to :ref:`mjexport.h<inHeader>`.
. Added ``mj_printFormattedData``, which accepts a format string for floating point numbers, for example to increase
precision.

General
^^^^^^^

7. MuJoCo can load `OBJ <https://en.wikipedia.org/wiki/Wavefront_.obj_file>`__ mesh files.

a. Meshes containing polygons with more than 4 vertices are not supported.
. In OBJ files containing multiple object groups, any groups after the first one will be ignored.
. Added (post-release, not included in the 2.1.2 archive) textured
`mug <https://github.com/google-deepmind/mujoco/blob/main/model/mug/mug.xml>`__ example model:

.. image:: images/changelog/mug.png
:width: 300px


. Added optional frame-of-reference specification to :ref:`framepos<sensor-framepos>`,
:ref:`framequat<sensor-framequat>`, :ref:`framexaxis<sensor-framexaxis>`, :ref:`frameyaxis<sensor-frameyaxis>`,
:ref:`framezaxis<sensor-framezaxis>`, :ref:`framelinvel<sensor-framelinvel>`, and
:ref:`frameangvel<sensor-frameangvel>` sensors. The frame-of-reference is specified by new :at:`reftype` and
:at:`refname` attributes.

. Sizes of :ref:`user parameters <CUser>` are now automatically inferred.

a. Declarations of user parameters in the top-level :ref:`size <size>` clause (e.g. :at:`nuser_body`,
:at:`nuser_jnt`, etc.) now accept a value of -1, which is the default. This will automatically set the value to
the length of the maximum associated :at:`user` attribute defined in the model.
. Setting a value smaller than -1 will lead to a compiler error (previously a segfault).
. Setting a value to a length smaller than some :at:`user` attribute defined in the model will lead to an error
(previously additional values were ignored).

. Increased the maximum number of lights in an :ref:`mjvScene` from 8 to 100.

. Saved XML files only contain explicit :ref:`inertial <body-inertial>` elements if the original XML included them.
Inertias that were automatically inferred by the compiler's :ref:`inertiafromgeom <compiler>` mechanism remain
unspecified.

. User-selected geoms are always rendered as opaque. This is useful in interactive visualizers.

. Static geoms now respect their :ref:`geom group<body-geom>` for visualisation. Until this change rendering of static
geoms could only be toggled using the :ref:`mjVIS_STATIC<mjtVisFlag>` visualisation flag . After this change, both
the geom group and the visualisation flag need to be enabled for the geom to be rendered.

. Pointer parameters in function declarations in :ref:`mujoco.h<inHeader>` that are supposed to represent fixed-length
arrays are now spelled as arrays with extents, e.g. ``mjtNum quat[4]`` rather than ``mjtNum* quat``. From the
perspective of C and C++, this is a non-change since array types in function signatures decay to pointer types.
However, it allows autogenerated code to be aware of expected input shapes.

. Experimental stateless fluid interaction model. As described :ref:`here <gePassive>`, fluid forces use sizes computed
from body inertia. While sometimes convenient, this is very rarely a good approximation. In the new model forces act
on geoms, rather than bodies, and have a several user-settable parameters. The model is activated by setting a new
attribute: ``<geom fluidshape="ellipsoid"/>``. The parameters are described succinctly :ref:`here<body-geom>`, but we
leave a full description or the model and its parameters to when this feature leaves experimental status.

Bug fixes
^^^^^^^^^

16. ``mj_loadXML`` and ``mj_saveLastXML`` are now locale-independent. The Unity plugin should now work correctly for
users whose system locales use commas as decimal separators.
. XML assets in VFS no longer need to end in a null character. Instead, the file size is determined by the size
parameter of the corresponding VFS entry.
. Fix a vertex buffer object memory leak in ``mjrContext`` when skins are used.
. Camera quaternions are now normalized during XML compilation.

Binary build
^^^^^^^^^^^^

20. Windows binaries are now built with Clang.