Testing on 50 million random doubles we have branchless clip is 1.14x faster than the branched version and branchless sign is 2.27x faster than the branched version.
PiperOrigin-RevId: 943812426
Change-Id: If8003a602365601a31bec1d8b080c44d16000a4e
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
Two performance optimizations for interpolated flex objects:
1. Hoist loop-invariant stride calculations in `mju_cellLookup` out of nested loops.
This reduces multiplications from 16 to 6 (linear) and 54 to 12 (quadratic)
per vertex.
2. Extract and consolidate optimized 3D interpolation logic into a new
reusable utility `mju_evalBasisArray` in `engine_util_misc.c`. This function
uses nested loops and precomputed 1D shape functions to avoid expensive
dynamic `phi` calls and branching, and leverages stack-buffered outputs to
eliminate compiler pointer-aliasing barriers. We propagate this optimization
to both kinematics (`mju_interpolate3D`) and constraint setup
(`engine_core_constraint.c`).
Together these changes yield a ~50% overall speedup in `mj_fwdKinematics` for interpolated flexes with ~10k vertices in the collision meshes and ~10 nodes in the deformation grid.
PiperOrigin-RevId: 922198093
Change-Id: I9c804e65cd532e2f9ac6e9a71d01c30cd64186fa
This change adds a new passive force computation for flexes with elastic2d="bend" and dof="trilinear". The bending energy is based on the squared difference of normals between adjacent face elements at their shared edge midpoint. The edge data is precomputed during model compilation and stored in flex_bending.
PiperOrigin-RevId: 910772638
Change-Id: I3b12c7b7f1ba6ac1875df495d89e8cfec921ca80
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
This is a more general API in preparation of a higher interpolation order
PiperOrigin-RevId: 820174741
Change-Id: I81bd52ab44e0485d72579e21d1c8a48a1b35ec3f
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
These functions names and argument ordering are more consistent with the rest of the API.
PiperOrigin-RevId: 643788290
Change-Id: I783eda8021b80b82098e23ed95669b102bb82508
That change removed some spurious contacts returned by mjc_BoxBox, but also removed some desirable contacts that occur during very deep penetration of two boxes (when one box is completely inside another box). This is now fixed.
PiperOrigin-RevId: 591036252
Change-Id: I84b51f2179fd6fe29618a4e908e86934c6fc6941
The box-box collider sometimes outputs bad contact points which are far outside one of the two boxes. This happens at configurations which are very rare numerically, but rare configurations (e.g. perfect box alignment) are often induced by the designer and the physics, making them actually not-so-rare.
Since the box collision functions are very difficult to understand, we circumvent the issue by extending the post processing code to detect and remove such contacts.
PiperOrigin-RevId: 589178197
Change-Id: I82b8a888ef04f9196111c960757e3314d0ab6d8e
Kyle Bayes