google-deepmind/mujoco 3.15.0

3.15.0

Repository: google-deepmind/mujoco

Tag: 3.15.0

Published: 2026-10-05T14:58:18Z

Prerelease: no

Release notes:

Version 3.15.0 (October 5, 2026)

General

1. `1aa68e1ca` .mjz archives written on Windows now always use / separators.

2. `1aa68e1ca` Assets in a meshdir or texturedir now resolve correctly in .mjz archives when rewritten or when the directory path is absolute, uses .., or uses a URI scheme.

Engine

> [!WARNING] > Breaking API changes > > 3. `b3dd9e617` Actuator dampratio now computes the reflected inertia > $m$ at mjModel.qpos0 as the operational-space inertia $(J M^{-1} J^T)^{-1}$ (averaged across force > outputs for multi-output actuators such as orientation), rather than summing > $\text{dof\\_M0}_j / J_j^2$ across degrees of freedom. This accounts for tendon and actuator armature as well > as off-diagonal inertial coupling, and avoids extreme damping values when a multi-DOF transmission has small > Jacobian entries. In practice, actuators using dampratio on multi-link kinematic chains may exhibit lower > damping than before, while actuators driving tendons or sites that span multiple joints will be damped much more > accurately instead of being overdamped. > > 4. `5023a4a50` Removed the deprecated internal flex collision option and associated evpair > structures.

5. `1b973add4` Added experimental simplified Stable Neo-Hookean elasticity for non-interpolated 3D flexes, enabled only through mjsFlex.elastic3d = 1. It projects the material Hessian to positive semidefiniteness for the solver and Rayleigh damping, and preserves the Saint Venant-Kirchhoff (StVK) default (0). SNH requires the discrete integrator. The setting is not available in MJCF.

6. `2742de438` The cached flex bending factor now retains cross-coordinate couplings between differently oriented vertex bodies.

7. `eed008905` Flex bending and stretching now include the motion and reaction forces of articulated vertex attachments. The discrete integrator supports these attachments with the CG solver; fixed and independent XYZ-slide attachments retain their optimized assembly. Elastic flexes attached to mocap bodies produce a compiler error.

8. `6224e95f6` Added single-shot multicontact for collisions with capsule geoms.

9. `ebfb4662d` Added the enclosed attribute to insidesite sensors, measuring how much an object juts out of a site (using directed Hausdorff distance) and reporting signed clearance/protrusion.

10. `f80ef4244` Fixed 64-bit model size narrowing in binary MJB serialization: `mj_saveModel` and `mj_loadModelBuffer` now accept `mjtSize` for buffer_sz, supporting models larger than 2 GiB.