Modify EigendecomposeStiffness to project out rigid body translations and rotations from the stiffness matrix eigenvectors. This prevents "ghost damping" from rigid body modes being incorrectly constrained. Update hollow_vs_solid.xml with solimp parameters for edge constraints. Adjust engine_core_constraint_test.cc to reflect the reduced number of equality constraints due to the projection.
PiperOrigin-RevId: 910631207
Change-Id: Ibaaa59bc030cfc6ae657d8f0d1b2a51002cc8d4e
The `vert0` array, used for parametric vertex coordinates in flexes, is now computed in the flex's local, unrotated frame when using interpolation. This ensures that the parametric coordinates are independent of the flex's initial orientation. A new test confirms that `flex_vert0` is identical for an unrotated and a rotated flex grid.
PiperOrigin-RevId: 908196464
Change-Id: I47d6bcc2bc5df581479d485480e0e947ec6d3ffd
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
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
The reference node positions and the positions used for computing stiffness eigenvectors were previously stored in world frame. However, the runtime expects these quantities in the unrotated local frame. This caused non-zero constraint residuals and simulation instability when the grid was rotated — either by the parent body's initial orientation, or by the flexcomp's own frame attributes.
Rather than tracking each rotation source individually, this change extracts the total grid rotation directly from the cell geometry. All node positions are then un-rotated before computing the stiffness matrix.
PiperOrigin-RevId: 903232388
Change-Id: If877af89025ce1e61a76b38c29403d593d892749
Previously specs that were attached to some parent spec would resolve its asset paths relative to the modelfiledir of the parent spec. This means path resolution would change depending on the source of the parent spec. Instead, this change makes asset file path resolution relative to the "owning spec" i.e. the spec where the asset was created.
This enables workflows such as loading a parent spec via resource provider, then loading a child spec via `from_zip` or in memory providing `spec.assets` and resolution will work as intended.
PiperOrigin-RevId: 903207910
Change-Id: Ia58020ab372a3ceadf31e804d145e2ae53d8e5f9
The previous implementation only checked whether grid cells contained mesh vertices to determine occupancy. For coarse meshes with large faces, most cells were incorrectly marked empty and pruned—even cells fully inside the object volume. This change improves the algorithm by:
- Marking cells that overlap with any mesh element's AABB as non-empty.
- For surface meshes, running a flood-fill from the grid boundary through non-overlapping cells to identify truly exterior cells. This preserves empty interior cells, preventing incorrect pruning of the object's core.
- For volumetric meshes, defaulting to element-AABB overlap detection directly.
Limitations for non-watertight meshes: If the mesh contains holes larger than the grid cell size, the flood-fill will leak into the interior. In this case, all non-element cells (including interior ones) will be marked as empty.
PiperOrigin-RevId: 902675331
Change-Id: I5a84303a33d5ca7436213e7ce9aca3806c9f5a0f
This overload allows `StringToVector` to accept a `char*` argument when parsing into a `std::vector<std::string>`, by converting the `char*` to `std::string` before processing.
PiperOrigin-RevId: 902611443
Change-Id: I2048918f915c1bac74522f368ea28f23ca9a6885
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 CL addresses link failures when building MuJoCo with GCC and Link Time Optimization (LTO) enabled:
- Declared the `StringToVector<std::string>(const std::string&)` specialization in `user_util.h` to prevent the compiler from incorrectly trying to instantiate the general template.
- Added an explicit instantiation for `StringToVector<unsigned char>(char*)` in `user_util.cc` to provide the definition needed by its `const std::string&` counterpart.
PiperOrigin-RevId: 902557141
Change-Id: I27b585cf1deb276d4150a5cbe6cf7e59c323a20a
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
Each mjEQ_FLEXSTRAIN equality now represents a single cell within a flex. This allows for more efficient sparse Jacobian computation by only considering the degrees of freedom of the nodes within each specific cell. This change gives a speedup of about 10x on a 3x3x3 model.
PiperOrigin-RevId: 902164069
Change-Id: I78eedf1d5cf39b8989fe9863c22d164922fc0efb
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
* Ensure compiler.usethread=0 is set before compilation in single-threaded WASM builds
* Explicitly enable exceptions for the single-threaded WASM module
* Test the single-threaded module in addition to the multi-threaded module in internal and external CI
* Consolidate wasm/tests/CMakeLists.txt into wasm/CMakeLists.txt, fixing the single-threaded benchmark test build which was missing shared linker flags
PiperOrigin-RevId: 901149728
Change-Id: If4946e29e5116610782d218906cf3f5940c1cdd0
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
This change disallows calling `mjs_delete` on an mjSpec that has been attached to another mjSpec via `mjs_attach`. Attempting to delete an element from an attached spec will now result in an error. The Python bindings for `mjSpec.delete` have been updated to raise a ValueError when this occurs.
PiperOrigin-RevId: 897266695
Change-Id: Ic0670125a3028191ec50eca890f02b5910ec8b03
- Remove `lugre:viscous`, should now be added directly to actuator `damping`. Trying to do this for the user was incompatible with default inheritance (compounding instead of overriding).
- Move voltage limiting from the `saturation` to the `controller` attribute.
- Fix indexing issues in default inheritance.
PiperOrigin-RevId: 897087642
Change-Id: I5388c2633e15c7e223992e7eb5d6a28db75a6438
Add a warning in user_model.cc if a flex is not rigid and has no edge equality constraints or passive forces (edge stiffness, edge damping, or vertex damping). Such flexes would not affect the simulation. A test case is added to verify the warning.
PiperOrigin-RevId: 889215981
Change-Id: I481128e1456921b632719547c676d201fdfbe931
Add a new mjpEncoder plugin type mirroring the existing mjpDecoder pattern.
Encoders serialize an mjSpec + mjModel to an mjResource for a given format.
New API functions:
- mjp_registerEncoder: globally register an encoder
- mjp_defaultEncoder: zero-initialize an encoder struct
- mjp_findEncoder: look up an encoder by filename extension or content type
The mjfEncode callback takes (mjSpec*, mjModel*, mjVFS*, mjResource*) and
returns 0 on success. Writing to mjResource keeps symmetry with the decoder
reading from mjResource and leaves the door open for writable resource providers.
PiperOrigin-RevId: 889187898
Change-Id: I180771b2255b91dea188ac5e2cdc3a8f0fb85364
The `vertcollide` attribute in flex and flexcomp contact specifications has been removed since the next mjWarp release will support flex collisions. This attribute was previously used to enable vertex-based collisions by adding sphere geoms at flex vertices. The functionality associated with this attribute has been deprecated and removed from the XML parser, documentation, and internal data structures. Affected example XML files have also been updated.
PiperOrigin-RevId: 885595503
Change-Id: I6a78975f1bc540c09ea8b5306ff3be0962b7ab24
Repro instructions (note compiler cache and threading must be enabled):
Assume we have a cube.stl mesh containing face data and the following XML:
<mujoco>
<asset>
<mesh name="cube" file="cube.stl"/>
<mesh name="unused" file="cube.stl"/>
</asset>
<worldbody>
<geom type="mesh" mesh="cube"/>
</worldbody>
</mujoco>
Suppose Thread A processes "cube" and Thread B processes "unused". Thread A will generate the mesh hull and will generate polygon data from faces from qhull. Thread B will NOT generate the mesh hull and will generate polygon data from faces coming from mesh file. Thread A beats Thread B to caching the mesh.
When "unused" is later pulled from the cache it gets the polygon data that was generated from "cube" which is not the same that was generated from "unused".
PiperOrigin-RevId: 878336494
Change-Id: I275b09b44490c54b2a5f09d91d0cc047026090f2
The `mjCOctree::ComputeSdfCoeffs` function has been replaced by `mjCOctree::ComputeSdf`. The new implementation removes the dependency on the `triangle_mesh_distance` library. Instead, it uses a provided `mjCBoundingVolumeHierarchy` to perform closest point queries on the mesh. The signed distance is computed by finding the closest triangle face via the BVH and determining the sign based on the dot product of the vector from the closest point on the triangle to the octree vertex and the triangle's normal.
Optional Laplacian smoothing has been added to the SDF coefficients. This helps smooth out potential discontinuities at octree level boundaries.
PiperOrigin-RevId: 875093374
Change-Id: I6fa53243a2dda107ccf255bc6b876ca5a4554d4f
Alessio Quaglino