Do not allow a mix of `elastic2d != none` with `dof = trilinear` since the latter assumes 3d elasticity.
Also, do not assume that `flex_interp > 0` in the engine. This will enable to use, e.g., `flex_interp = -1` to mean a linear surface finite element instead of a 3d finite element which is currently identified with `flex_interp = 1`.
PiperOrigin-RevId: 903852035
Change-Id: Ia6290b4a05e9e510ffb7f36d141cd525b40d3110
This change introduces an optimization for flexcomp objects defined by a mesh. It identifies grid cells that do not contain any mesh vertices and marks them as empty. Nodes that are exclusively part of empty cells are pinned, preventing them from moving. Stiffness computations are skipped for empty cells, reducing computational cost. The total mass is now distributed only among the non-pinned nodes.
PiperOrigin-RevId: 902565735
Change-Id: Id0a9a685536d5e18a3e42124a25ab08ff3a918f2
This provides a reduction from 26 to 18 constraints for trilinear and from 162 to 75 for quadratic. The assembly of the constraints becomes trivial. In total the speedup for a trilinear 3x3x3 grid is about 3x.
PiperOrigin-RevId: 902502398
Change-Id: I764772c7adef78da5a644f64701f842d36e4b543
The flex interpolation stiffness matrix within the implicit/implicitfast solvers is now built and factorized in a banded format instead of a dense one. This involves:
- Calculating the bandwidth based on the sparsity of the mass/damping matrix and the connectivity within flex cells.
- Allocating and populating a banded matrix `H`.
- Using `mju_cholFactorBand` and `mju_cholSolveBand` for factorization and solving.
This change improves performance for flexes with many DOFs but local coupling.
PiperOrigin-RevId: 901297952
Change-Id: I3efe06353d1903ea65ab30dc49685cede228bb68
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
This change introduces `nflexstiffness` and `flex_stiffnessadr` to allow flex stiffness matrices to have sizes other than the fixed 21 per element. Higher-order flexes can now store larger stiffness matrices based on their number of nodes. The `flex_stiffnessadr` array provides the starting index for each flex's stiffness data within the `flex_stiffness` array.
PiperOrigin-RevId: 899632263
Change-Id: Ie49182c46c3777acf0c6b492345edfcf62fb5e44
The derivatives of actuator velocity with respect to generalized velocities were incorrectly computed when the actuator force was limited by `forcerange`. This CL adds a check to zero out these derivatives when the actuator force is at its upper or lower limit, as the force is no longer a function of velocity in this clamped state.
PiperOrigin-RevId: 868818281
Change-Id: I89742a3f04989dd11f9cfada107200015b1472a7
The derivative calculation for actuator velocity in implicit integrators now correctly accounts for the `actearly` flag, using the next activation value when `actearly` is true.
PiperOrigin-RevId: 868598722
Change-Id: Ia180afb15b31a718170aeaf9d4ac514bb9e6073b
Fixes a bug where the derivative of the actuator force with respect to the generalized velocities (used in implicit and implicitfast integrators) was failing to take into account disabled actuators.
Fixes#1838
PiperOrigin-RevId: 657193960
Change-Id: Id8c0ab863a39e2a01cd2703774f460e9731b4807
These functions names and argument ordering are more consistent with the rest of the API.
PiperOrigin-RevId: 643788290
Change-Id: I783eda8021b80b82098e23ed95669b102bb82508
Also rename arguments and loop variables in `addJTBJSparse` for additional clarity.
PiperOrigin-RevId: 534908360
Change-Id: I143ef5aef7ff90091369d408740f7f44d9e19378
Alessio Quaglino