Mujoco

Open Sourcing

1. MuJoCo is now fully open-source software. Newly available top level directories are:
1. `src/`: All source files. Subdirectories correspond to the modules described in the Programming chapter [introduction](https://mujoco.readthedocs.io/en/2.2.0/programming.html#introduction):
* `src/engine/`: Core engine.
* `src/xml/`: XML parser.
* `src/user/`: Model compiler.
* `src/visualize/`: Abstract visualizer.
* `src/ui/`: UI framework.
2. `test/`: Tests and corresponding asset files.
3. `dist/`: Files related to packaging and binary distribution.

2. Added [contributor's guide](https://github.com/deepmind/mujoco/blob/2.2.0/CONTRIBUTING.md) and [style guide](https://github.com/deepmind/mujoco/blob/2.2.0/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.

4. 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 [velocity actuators](https://mujoco.readthedocs.io/en/2.2.0/XMLreference.html#velocity). For more details, see the [Numerical Integration](https://mujoco.readthedocs.io/en/2.2.0/computation.html#geintegration) section.

5. Added `actlimited` and `actrange` attributes to [general actuators](https://mujoco.readthedocs.io/en/2.2.0/XMLreference.html#general), for clamping actuator internal states (activations). This clamping is useful for integrated-velocity actuators, see the [Activation clamping](https://mujoco.readthedocs.io/en/2.2.0/modeling.html#cactrange) section for details.

6. `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".

7. 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>`.

8. The default shadow resolution specified by the [shadowsize](https://mujoco.readthedocs.io/en/2.2.0/XMLreference.html#quality) attribute was increased from 1024 to 4096.

9. Saved XMLs now use 2-space indents.

Bug fixes

10. Antialiasing was disabled for segmentation rendering. Before this change, if the [offsamples](https://mujoco.readthedocs.io/en/2.2.0/XMLreference.html#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 `offsamples` is ignored during segmentation rendering.

11. 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.

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

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Update 1 (27 May 2022): Replaced Linux tarball to fix RPATH on the sample binaries. No change in functionality.

General

1. Added an experimental feature: multi-contact convex collision detection, activated by an enable flag. See full
description [here](https://mujoco.readthedocs.io/en/2.1.5/XMLreference.html#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. Fixes https://github.com/deepmind/dm_control/issues/283.

3. 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. Fixes https://github.com/deepmind/mujoco/issues/238.

General

1. MuJoCo now uses [GLAD](https://github.com/Dav1dde/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.

2. Add 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. Fix a bug in simulate where pressing '[' or ']' when a model is not loaded causes a crash.

5. Contact frame visualisation is added to the Simulate GUI.

6. Rename "set key", "reset to key" to "save key" and "load key", respectively.

7. Change 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` now zeroes out the `solver_nnz` field.

9. Remove 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.

This is a minor release, handling issues discovered after the launch of 2.1.2.

General

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

Python bindings

3. Added a `free()` method to `MjrContext`, rather than relying on the object destructor.
4. Enums now support arithmetic and bitwise operations with numbers.

Bug fixes

5. Fixed a rendering bug for planes, introduced in 2.1.2. This broke maze environments in [`dm_control`](https://github.com/deepmind/dm_control).

New modules
1. Added new [Python bindings](https://mujoco.readthedocs.io/en/2.1.2/python.html), which can be installed via `pip install mujoco`, and imported as `import mujoco`.
2. Added new [Unity plug-in](https://mujoco.readthedocs.io/en/2.1.2/unity.html).
3. 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/deepmind/mujoco/blob/2.1.2/include/mjtnum.h).
5. Renamed header `mujoco_export.h` to [mjexport.h](https://github.com/deepmind/mujoco/blob/2.1.2/include/mjexport.h).
6. 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.
- 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.
8. Added optional frame-of-reference specification to: [`framepos`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-framepos), [`framequat`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-framequat), [`framexaxis`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-framexaxis), [`frameyaxis`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-frameyaxis), [`framezaxis`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-framezaxis), [`framelinvel`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-framelinvel), and [`frameangvel`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-frameangvel) sensors. The frame-of-reference is specified by new `reftype` and `refname` attributes.
9. Sizes of [user parameters](https://mujoco.readthedocs.io/en/2.1.2/modeling.html#cuser) are now automatically inferred.
- Declarations of user parameters in the top-level [size](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#size) clause (e.g. `nuser_body`, `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 `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 `user` attribute defined in the model will lead to an error (previously additional values were ignored).
10. Increased the maximum number of lights in an [`mjvScene`](https://mujoco.readthedocs.io/en/2.1.2/APIreference.html#mjvscene) from 8 to 100.
11. Saved XML files only contain explicit [inertial](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#inertial) elements if the original XML included them. Inertias that were automatically inferred by the compiler's [inertiafromgeom](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#compiler) mechanism remain unspecified.
12. User-selected geoms are always rendered as opaque. This is useful in interactive visualizers.
13. Static geoms now respect their [geom group](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#geom) for visualisation. Until this change rendering of static geoms could only be toggled using the [`mjVIS_STATIC`](https://mujoco.readthedocs.io/en/2.1.2/APIreference.html#mjtvisflag) visualisation flag . After this change, both the geom group and the visualisation flag need to be enabled for the geom to be rendered.
14. Pointer parameters in function declarations in [mujoco.h](https://github.com/deepmind/mujoco/blob/2.1.2/include/mujoco.h) 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.
15. Experimental stateless fluid interaction model. As described [here](https://mujoco.readthedocs.io/en/2.1.2/computation.html?highlight=passive#passive-forces), 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 [here](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html?highlight=geom#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.
17. 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.
18. Fix a vertex buffer object memory leak in `mjrContext` when skins are used.
19. Camera quaternions are now normalized during XML compilation.

Binary build
20. Windows binaries are now built with Clang.

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Python bindings `2.1.2.post1` (16 March 2022)
- Removed a stray print statement in `__init__.py`.
- Bundled `libglewegl.so` for Linux now has a `DT_NEEDED` entry on `libOpenGL.so.0`. (The download packages for Linux below have also been updated with this.)
- The sdist can now be built with GCC.

API changes

1. Added ``mj_printFormattedModel``, which accepts a format string for floating point numbers, for example to increase precision.
2. Added ``mj_versionString``, which returns human-readable string that represents the version of the MuJoCo binary.
3. Converted leading underscores to trailing underscores in private instances of API struct definitions, to conform to reserved identifier directive, see [C standard: Section 7.1.3](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf).

This is a minor breaking change. Code which references private instances will break. To fix, replace leading underscores with trailing underscores, e.g. `struct _mjModel` becomes `struct mjModel_`.

General

4. Safer string handling: replaced `strcat`, `strcpy`, and `sprintf` with `strncat`, `strncpy`, and
`snprintf` respectively.
5. Changed indentation from 4 spaces to 2 spaces everywhere.

Bug Fixes

6. Fixed reading from uninitialized memory in PGS solver.
7. Computed capsule inertias are now exact. Until this change, capsule masses and inertias computed by the
[`compiler`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#compiler)'s `inertiafromgeom` mechanism were approximated by a cylinder, formed by the capsule's cylindrical middle section, extended on both ends by half the capsule radius. Capsule inertias are now computed with the [Parallel Axis theorem](https://en.wikipedia.org/wiki/Parallel_axis_theorem>), applied to the two hemispherical end-caps.

This is a minor breaking change. Simulation of a model with automatically-computed capsule inertias will be numerically different, leading to, for example, breakage of golden-value tests.
8. Fixed bug related to [`force`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-force) and [`torque`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-force) sensors. Until this change, forces torques reported by F/T sensors ignored out-of-tree constraint wrenches except those produced by contacts. Force and and torque sensors now correctly take into account the effects of [`connect`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#equality-connect) and [`weld`](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#equality-connect) constraints.

Forces generated by [spatial tendons](https://mujoco.readthedocs.io/en/2.1.2/XMLreference.html#sensor-force) which are outside the kinematic tree (i.e. between bodies which have no ancestral relationship) are still not taken into account by force and torque sensors. This remains a future work item.

Code samples

9. `testspeed`: Added injection of pseudo-random control noise, turned on by default. This is to avoid settling into some fixed contact configuration and providing an unrealistic timing measure.
10. `simulate`:

- Added slower-than-real-time functionality, which is controlled via the '+' and '-' keys.
- Added sliders for injecting Brownian noise into the controls.
- Added "Print Camera" button to print an MJCF clause with the pose of the current camera.
- The camera pose is not reset when reloading the same model file.

Updated dependencies

11. `TinyXML` was replaced with `TinyXML2` 6.2.0.
12. `qhull` was upgraded to version 8.0.2.
13. `libCCD` was upgraded to version 1.4.
14. On Linux, `libstdc++` was replaced with `libc++`.

Binary build

15. MacOS packaging. We now ship Universal binaries that natively support both Apple Silicon and Intel CPUs.

- MuJoCo library is now packaged as a [Framework Bundle](https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/BPFrameworks/Concepts/FrameworkAnatomy.html), allowing it to be incorporated more easily into Xcode projects (including Swift projects). Developers are encouraged to compile and link against MuJoCo using the `-framework mujoco` flag, however all header files and the ``libmujoco.2.1.1.dylib` library can still be directly accessed inside the framework.
- Sample applications are now packaged into an Application Bundle called `MuJoCo.app`. When launched via GUI, the bundle launches the `simulate` executable. Other precompiled sample programs are shipped inside that bundle (in `MuJoCo.app/Contents/MacOS`) and can be launched via command line.
- Binaries are now signed and the disk image is notarized.

16. Windows binaries and libraries are now signed.
17. Link-time optimization is enabled on Linux and macOS, leading to an average of ~20% speedup when benchmarked on
three test models (`cloth.xml`, `humanoid.xml`, and `humanoid100.xml`).
18. Linux binaries are now built with LLVM/Clang instead of GCC.
19. An AArch64 (aka ARM64) Linux build is also provided.
20. Private symbols are no longer stripped from shared libraries on Linux and MacOS.

Sample models

21. Clean-up of the `model/` directory.

- Rearranged into subdirectories which include all dependencies.
- Added descriptions in XML comments, cleaned up XMLs.
- Deleted some composite models: `grid1`, `grid1pin`, `grid2`, `softcylinder`, `softellipsoid`.

22. Added descriptive animations in `docs/images/models/`

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EDIT (30/12/2021 21:45 UTC): Added import libraries `mujoco.lib` and `mujoco_nogl.lib` to the Windows release package.

EDIT (16/12/2021 21:10 UTC): We've updated the download packages to reflect minor changes in https://github.com/deepmind/mujoco/commit/ee39340ae783f6944f74168d852d7ac1664268c0. These changes only affect the bundled code and asset files. The libraries and binaries behave identically to the original packages released earlier today.