Previously shell mode required cellcount=1 along at least one axis. This CL
adds support for cellcount > 1 in all three axes by pinning interior grid nodes
to the parent body and reconstructing their positions from boundary nodes via
Transfinite Interpolation (TFI).
PiperOrigin-RevId: 924314800
Change-Id: I8c2438f4866dd4133feed65f535a1ab69f0c9188
Also add MJTOL_SCALE to fixture to allow tests to be run with zero tolerance. This is useful when assesing the impact of code changes (A/B comparison of failure values)
PiperOrigin-RevId: 924219083
Change-Id: Ifdd09ac850904ca8dd79179930ce738a4b37d284
When elastic2d="stretch" is set on an interpolated flexcomp, treat the bounding box boundary as membrane elements rather than volumetric cells. This computes plane-stress stiffness over the boundary faces and updates the runtime force/derivative kernels accordingly.
Interior vertex tracking (moving vertices that follow the deforming shell) is not yet implemented so all mesh vertices need to be on the bounding box surface or the background grid should have no interior nodes (i.e. cellcount should be 1 on at least one axis).
PiperOrigin-RevId: 907654080
Change-Id: I51b90e2f6a1d1b036f9604e42de20e377dc5d3f9
This change introduces a `flex_cellcount` field to `mjModel` to specify the number of cells in each dimension for interpolated flexes. The stiffness computation, passive force calculation, and Jacobian derivatives are updated to operate on a per-cell basis, significantly improving performance by localizing computations to the nodes within each cell.
PiperOrigin-RevId: 901216393
Change-Id: Ic23132e609de11e71bb7fef8d1f139daad2ec264
The functions and associated tests related to managing time-stamped data buffers have been renamed from `mju_delay*` to `mju_history*` to better reflect their general purpose beyond just handling delays.
PiperOrigin-RevId: 866978339
Change-Id: I8655e91bce783287ad2adc412d13a1c39aa2c322
These flexes use only 24 DOFs (3 per vertex of the bounding box), while colliding with the full high resolution mesh.
On an 8x8x8 cube, the performance using DOFs at all vertices is
```
Simulation time : 18.74 s
Steps per second : 533
Realtime factor : 0.53 x
Time per step : 1874.4 µs
Contacts per step : 114.88
Constraints per step : 3322.51
Degrees of freedom : 1536
```
With the new implementation, it is the following:
```
Simulation time : 1.82 s
Steps per second : 5507
Realtime factor : 5.51 x
Time per step : 181.6 µs
Contacts per step : 38.84
Constraints per step : 155.36
Degrees of freedom : 24
```
PiperOrigin-RevId: 721008829
Change-Id: I833df027527db578d86667cc4b24295bcf6f7d22
- `muscle` actuators take a new `tausmooth` attribute (defaults to 0) which when positive, smooths the transition between activation and deactivation timescales.
- `mju_muscleDynamics` takes 3 parameters, adding width of smoothing sigmoid.
PiperOrigin-RevId: 531473354
Change-Id: I8ab6c0289ff04437e798c3ca6edda132a30fcc31
Yuval Tassa