- Applies to [orientation specifiers](https://mujoco.readthedocs.io/en/latest/modeling.html#frame-orientations) in `body`, `inertial`, `geom`, `site`, `camera`.
- Before this change the check was done only for multiple *alternative* specifiers, but not for `quat` and an alternative specifier.
- Moved the check from the compiler to the parser.
- Added tests.
PiperOrigin-RevId: 453201981
Change-Id: I20907361f211dae904e734cd083e9df0efe4f654
Inertias of moving bodies are enforced to be greater mjMINVAL at model compilation, there is no need to enforce inertias at mesh load time. Tiny meshes could be static or part of a larger geom assembly, in which case their tiny inertia is not a problem.
Also, make error message for small masses/inertias more precise.
PiperOrigin-RevId: 451625216
Change-Id: I4b48d7a881e620d6fbb591ec77fbdacc7c03496c
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.
A new implicit-in-velocity integrator is implemented using the analytic derivatives. This integrator lies between the Euler and Runge Kutta integrators in terms of both stability and computational cost.
PiperOrigin-RevId: 450377010
Change-Id: Ie192b441876c22e732fb749333926f296e0a09cc
Alessio Quaglino