Jiminy-py

This release fixes the last remaining blocking issues with Panda3d in order to make it the default viewer backend. So, starting from this point, it will be the default backend, useless for interactive environment like Jupyter, for which Meshcat is still the only appropriate alternative. In addition URDF and meshes associated with Atlas have been updated to make it look better:

<p align="center"><img src="https://user-images.githubusercontent.com/17752950/110535380-7c57d680-8120-11eb-892f-57ff80e401f5.png" width="350"></p>

Improvements

* [jiminy/viewer] Fallback to software rendering with panda3d if necessary.
* [jiminy/viewer] Limit Panda3d framerate to 30FPS to avoid consuming too much resources.
* [jiminy/viewer] Do not shrink legend automatically and slightly increase size on Panda3d.
* [jiminy/viewer] Zoom out default relative camera pose for travelling.
* [gym/common/envs] Automatically update rendering after 'reset' if available.
* [misc] Enable 'panda3d' by default instead of 'meshcat'.

Bug fixes

* [misc] Fix viewer replay on Windows by not removing 'Pinocchio::interpolate' from build anymore.
* [jiminy/simulator] Fix viewer not opening graphical window after closing it once.
* [jiminy/viewer] Fix widgets positioning and scaling on Panda3d.
* [jiminy/viewer] Improve exception handling if window closed during replay to avoid deadlock.
* [jiminy/viewer] Fix panda3d offscreen rendering not always updated before capturing frame.
* [jiminy/viewer] Fix panda3d mesh loader 'assimp' specific path formatting on Windows.
* [gym/common/envs] Fix keyword arguments forwarding for WalkerEnvs class.

Miscellaneous

* [core] Minor improvement of robot weak_ptr management for sensors/motors.
* [jiminy/simulator] Rename 'disable_flexiblity_data' or 'enable_flexiblity_data' for clarity.
* [gym/examples] Rllib 'test' method now returns the environment used for testing.
* [misc] Globally less restrictive Python requirements by using different specifications depending on the platform.
* [misc] Update atlas URDF and meshes to improve rendering.

Panda3d rendering backend support has been greatly improved. It should now works out-of-the-box on any hardware and platform. Meshcat-exclusive features has been ported to Panda3D (watermark and legend), and new Panda3D-exclusive simulation time clock is now available! The recording speed is much faster than meshcat (faster than recording duration at 30FPS and 1000x1000 resolution for 'mp4' format) and supports offscreen rendering without X-server. In addition, Python3.9 pre-built wheels are now provided on any platform. Finally, internal time steps management issues have been fixed, most affecting fixed timestep steppers.

New features

* [jiminy/viewer] Add support of watermark for panda3d.
* [jiminy/viewer] Add support of legend and watermark at Viewer level for Meshcat and Panda3d.
* [jiminy/viewer] Add option to enable clock during replay and recording using panda3d backend.

Improvements

* [core] Increase maximum simulation timestep for RL requirement.
* [jiminy/viewer] Do not open graphical window if possible by default when video recording is requested.
* [jiminy/viewer] Convert Python location meshcat recorder import warning into exception only raised at instantiation.
* [jiminy/viewer] Significant improvement of video recording speed for Panda3D. Record in .webm (slow) or .mp4 (6x faster).
* [gym/common/envs] Make sure the initial posture is close to neutral yet always valid.

Bug fixes

* [core] Fix wrong internal stepper timestep if fixed.
* [jiminy/viewer] Fix meshcat `wait` doing nothing.
* [jiminy/viewer] Fix panda3d black-screen issues.
* [jiminy/viewer] Fix support of Windows 10 for Panda3d backend.
* [gym/examples] Fix Rllib tools for env without reward threshold.

Miscellaneous

* [jiminy/viewer] Make sure only one graphical window can be opened locally.
* [misc] Use same steppers and timesteps than official Classic Control learning environment whenever possible.
* [misc] Remove 'jiminy' prefix from learning envs register id since it is redundant with namespace.
* [misc] Add wheels for Python3.9. From now on, only many2014 wheels will be provided instead of manylinux2010.

This release introduces first Mujoco-like locomotion learning environment in Jiminy [Ant](https://gym.openai.com/envs/Ant-v2/). An example script successfully training it using TD3 algorithm in Rllib is provided. In addition, several bugs have been addressed, mainly affecting video recording.

Improvements

* [jiminy/simulator] Allow chaining rendering methods.
* [gym/common/utils] Add full support of 'gym.spaces.Tuple'.
* [gym/common/envs] Fix 'render' method not call by env before replaying.
* [gym/common/envs] Enable traveling by default if robot has freeflyer.
* [gym/envs] Add mujoco-like Ant learning environment.

Bug fixes

* [core] Fix 'interpolate' utility.
* [jiminy/viewer] Fix traveling.
* [gym/common/envs] Clip returned observation systematically to avoid out-of-bounds errors.

Miscellaneous

* [gym/toolbox] Consistent addon package hierarchy.
* [gym/example] Refactor examples folder architecture to be easier to extend.
* [gym/example] More generic tools for Rllib. Add Ant TD3 Rllib example.
* [misc] Minor rework of acrobot and cartpole toy models.

This release introduces impulse-like contact model, which has became very popular since the last few years. In broad terms, it maximizes the energy dissipation resulting from contact with the ground, in such a way that the position of the contact points is critically damped with predefined natural frequency (corresponding to solving a LCP internally, see Mujoco [documentation](http://www.mujoco.org/book/computation.html) and [paper](https://homes.cs.washington.edu/~todorov/papers/TodorovICRA14.pdf) for reference). Even though it is not a phenomenological model, it features many very interesting properties, among which allowing very large fixed integration timestep (up to 10ms suing Runge Kutta 4), and smoothing ground reaction forces. Those properties are not essential in robotics to design controllers using classical control theory, but it turns out to be very beneficial when it comes to reinforcement learning, presumably because it makes the state-action mapping much more regular, enabling to learn control policies for complex very dynamic locomotion tasks. Learning examples and tutorials are coming !

In addition, the spring-damper contact model has been greatly simplified to use standard coulomb friction model, and a few significant bugs have been addressed.

New features

* [core] Add new impulse-like contact model.

Improvements

* [core] Check if initial configuration is valid at float precision instead of double then normalized to avoid casting issue in Python.
* [core] Change contacts/bounds spring-damper model to clamp the whole force rather than sole velocity-related component.
* [core] Remove stiction from spring-damper model.
* [python/simulator] Do not fill progress bar if aborted.
* [python/simulator/plot] Add parameter to disable plotting flexibilities. Automatically adjust layout.
* [python/viewer] Add option to only replay specific time interval. Enable to specify unique xyz_offset for replay.

Bug fixes

* [core] Fix inertia bias returning improper matrix.
* [gym/common/envs] Enforce deepcopy of observation and information before returning it to avoid any issue with replay buffer.

Miscellaneous

* [core] Add proper constraints holder to ease implementation of impulse contact model.
* [core] Rename Explicit Euler in Euler Explicit for consistency with Runge Kutta steppers.
* [core] Compute FixedFrameConstraint jacobian and drift LOCAL_WORLD_ALIGNED. Add Baumgarte stabilization.

This release brings minor performance improvement. It is mainly intended to improvement overall code quality and consistency with standard naming conventions (essentially Mujoco terminology). A convenience tool to interpolate trajectories in Lie group space has also been added.

New features

* [core|python/viewer] Provide generic interpolation method for configuration evolution over time. Use it in Python viewer.

Improvements

* [core] Compute subtree coms by default.
* [core] Do not compute 'oMf' for 'JOINT' and 'BODY' frames but rather copy data from 'oMi' and 'oMf'.
* [core] Improvement breakpoint management to avoid skipping controller/sensor updates.
* [core] Return static variables for Robot 'getControlLimit' and 'getArmatures' to avoid memory allocations.
* [core] Set 'command' and 'u_custom' to zero automatically before calling callbacks.
* [core] Improve vector 'clamp' utility to avoid memory allocation.
* [core/python] Make sure registered variables vector is 1D.
* [core|python] Add option to monitor motor efforts and plot them by default instead of command.
* [python/robot] Enable setting options only partially.
* [python/dynamics] Add optional flag to update collisions. Fix com jacobian not computed even if requested.
* [python/simulator] Do not forbid to render system at if no simulation is running.
* [gym/common] Ensure float64 action buffer for compatibility with register_variable telemetry.
* [gym/common/envs] Increment 'num_steps' only at the end of successful step, not right before integration.
* [gym/common/envs] Set robot in neutral configuration at init.

Bug fixes

* [core] Fix edge case in controller breakpoints management.
* [gym/common/envs] Fix edge case for robot without sensors.
* [gym/common/envs] Do not enforce position/velocity/effort bounds at _setup to avoid inconsistent observation/action spaces bounds.

Miscellaneous

* [misc] Move to C++17 for dependencies.
* [core] Rename 'rotorInertia' in 'armature' to be consistent with mujoco and clearer that it is joint side.
* [core] Rename 'EffortLimit' in 'ControlLimit' to avoid redundancy with pinocchio::Data and explicit it is motor-side.
* [core] Rename 'ControlLimit' in 'CommandLimit' for consistency.
* [core] Rename 'u_command' in 'command' to clarify it does not have to be an effort.
* [core] Add dedicated 'u_custom' field for controller's internal dynamics.
* [core] Replace 'u' with more specific variable name when possible.
* [core] Split evaluation of custom internal dynamics from position/velocity bounds and flexibility dynamics.

Another small release consisting mainly in bug fixes. In addition, a new type of pre-defined visco-elastic coupling force has been added, acting independently in each direction instead of only along coupling direction.

New features

* [core] Add non-directional visco-elastic coupling force (acting independently in each direction).

Improvements
* [core] Fix adaptive RK dopri stepper MAX_FACTOR wrongly scaled by SAFETY factor.
* [gym/common/envs] Do not log internal steps in debug mode to keep log consistent with experience replay.

Bug fixes

* [core] Fix visco-elastic directional coupling force.
* [core] Fix pinocchio_data updated with joint forces not taking into account the external forces.
* [core] Fix telemetry logging failed internal stepper steps.
* [core] Fix wrong computation of multi-systems coupling forces.
* [python/viewer] Fix replay using rigid instead of flexible model.
* [python/viewer] Fix mesh path on windows.

Miscellaneous

* [gym/common] Rename 'size' argument of 'sample' method in 'shape' for consistency with standard API.