Version 2.3.6

[saran-t]

NOTE: MuJoCo 2.3.6 is the last version to officially support Python 3.7.

Models

1. Added 3x3x3 cube example model. See README for details.

Bug fixes

2. Fixed a bug that was causing an incorrect computation of the mesh bounding box and coordinate frame if the volume was invalid. In such case, now MuJoCo only accepts a non-watertight geometry if shellinertia is equal to true.
3. Fixed the sparse Jacobian multiplication logic that is used to compute derivatives for tendon damping and fluid force, which affects the behaviour of the implicit and implicitfast integrators.
4. Fixes to mj_ray, in line with geom visualisation conventions:
   • Planes and height-fields respect the geom_group and flg_static arguments. Before this change, rays would intersect planes and height-fields unconditionally.
   • flg_static now applies to all static geoms, not just those which are direct children of the world body.

Plugins

5. Added touch-grid sensor plugin. See documentation for details, and associated touch_grid.xml example model. The plugin includes in-scene visualisation.
6. Added Visualization tab to simulate UI, corresponding to elements of the visual MJCF element. After modifying values in the GUI, a saved XML will contain the new values. The modifiable members of mjStatistic (extent, meansize and center) are computed by the compiler and therefore do not have defaults. In order for these attributes to appear in the saved XML, a value must be specified in the loaded XML.
7. Increased text width for UI elements in the default spacing.

General

8. Added mj_getState and mj_setState for getting and setting the simulation state as a concatenated vector of floating point numbers. See the State section for details.
9. Added mjContact.solreffriction, allowing different solref parameters for the normal and frictional axes of contacts when using elliptic friction cones. This attribute is required for elastic frictional collisions, see associated example model mimicking the spin-bounce recoil behaviour of elastic rubber balls. This is an advanced option currently only supported by explicit contact pairs, using the solreffriction attribute.
10. Added mjd_inverseFD for finite-differenced inverse-dynamics derivatives.
11. Added functions for operations on banded-then-dense “arrowhead” matrices. Such matrices are common when doing direct trajectory optimization. See mju_cholFactorBand documentation for details.
12. Added mj_multiRay function for intersecting multiple rays emanating from a single point. This is significantly faster than calling mj_ray multiple times.
13. Ray-mesh collisions are now up to 10x faster, using a bounding volume hierarchy of mesh faces.
14. Increased mjMAXUIITEM (maximum number of UI elements per section in Simulate) to 100.
15. Added documentation for resource providers.
16. Changed the formula for mju_sigmoid, a finite-support sigmoid $s: \mathbf{R} \rightarrow [0, 1]$. Previously, the smooth part consisted of two stitched quadratics, once continuously differentiable. It is now a single quintic, twice continuously differentiable:

$$ s(x) = \begin{cases} 0, & & x \le 0 \\ 6x^5 - 15x^4 + 10x^3, & 0 \lt & x \lt 1 \\ 1, & 1 \le & x \qquad \end{cases} $$

17. Added optional tausmooth attribute to muscle actuators. When positive, the time-constant $\tau$ of muscle activation/deactivation uses mju_sigmoid to transition smoothly between the two extremal values given by the Millard et al. (2013) muscle model, within a range of width tausmooth. See Muscle actuators for more details. Relatedly, mju_muscleDynamics now takes 3 parameters instead of 2, adding the new smoothing-width parameter.
18. Moved public C macro definitions out of mujoco.h into a new public header file called mjmacro.h. The new file is included by mujoco.h so this change does not break existing user code.
19. Added instrumentation for the Address Sanitizer (ASAN) and Memory Sanitizer (MSAN) to detect memory bugs when allocating from the mjData stack and arena.
20. Removed pstack and parena from the output of mj_printData, since these are implementation details of the mjData allocators that are affected by diagnostic paddings in instrumented builds.
21. Removed the mj_activate and mj_deactivate functions. These had been kept around for compatibility with old user code from when MuJoCo was closed source, but have been no-op functions since open sourcing.

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This discussion was created from the release 2.3.6.

[stm32f303ret6]

really nice feature the improvements of mj_multiRay and mj_ray, congrats