- Add `qH` and `qHDiagInv` to `mjData` to save factorized modified inertia.
- Add `mj_EulerSkip`, `mj_implicitSkip`, to `engine_forward.c`.
- Using the above functions, implement `mj_stepSkip` in `engine_derivative.c`.
- Add `mjd_stepFD` and `mjd_transitionFD` to `engine_derivative.c` to compute `mj_step` Jacobians.
- Exploit "Skip" functionality for speed.
- Correctly handle quaternion derivatives.
- Handle warmstarts and control limits.
PiperOrigin-RevId: 456584811
Change-Id: Iee8541f11e7b66feb8f431cb102d9bbe65461f79
Before this change, xipos[0,1,2] was only set to 0 by mj_resetData zeroing the entire buffer.
When using mj_resetDataDebug, the value would be wrong.
PiperOrigin-RevId: 450939814
Change-Id: I887dd977161c7d132a80b766db7be23350ffb50b
Saran Tunyasuvunakool