The obj_decoder plugin is updated to parse line segments ('l') from OBJ files and represent them as degenerate triangles. The user_flexcomp compiler now supports flex dimensions of 1, using these parsed line segments to define the 1D flex elements. The compile sample's error reporting is also improved.
PiperOrigin-RevId: 928566870
Change-Id: I6920729d1b1d5aeb391401c3245ebb1d4784c190
The field now stores either an approximate or exact diagonal of the constraint matrix A, so the name is made more general.
PiperOrigin-RevId: 924244954
Change-Id: I62b2f76531fb88b7b3bf96e6769940197596702b
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
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 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
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 `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
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
This change introduces methods to cache and load the computed stiffness matrix and nodal masses for flex elements. The cache key is generated based on material properties (Young's modulus, Poisson's ratio), interpolation order, and the bounding box of the flex. This avoids redundant expensive computations when compiling models with identical flex definitions.
PiperOrigin-RevId: 874689771
Change-Id: I6d1e299baf294a984b507e2a2602b2c068610536
Fix a crash and dimension mismatch issue in user_flexcomp when dealing with interpolated="true" meshes that contain unused vertices. Previously, vertbody would correspond only to used vertices while vert included all vertices, leading to assertions or out-of-bounds access. Also enable node pinning for interpolated meshes.
PiperOrigin-RevId: 865881995
Change-Id: Id150f00f22b5f48896ffbffddf03c57b252de8c0
The BVH is used also for computing normalized vertex coordinates in the trilinear interpolation, so we need to compute it also when the flex cannot collide.
PiperOrigin-RevId: 756349244
Change-Id: Ib397c472e31251df5a7ea85850d83a62f3b2c949
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
`flex_xvert0` stored the Cartesian position of the vertices in `qpos0`. This array was unused, so it is now replaced with `flex_vert0`, which still contains the positions of the vertices, but normalized on the bounding box of the flex so that the coordinates are in `[0,1]^m->flex_dim`. This will be useful in the future for using different interpolation methods for computing flex deformations.
PiperOrigin-RevId: 691779361
Change-Id: I5c4223103cd4558f4e268fe3e8d8177541e4754f
Replaced "shark" test models with lighter models to speed up tests.
END_PUBLIC.
- procedurally generated light cube
- replaced shark GMSH with cube for all tests with extension GMSH
- Reduced size of shark model used for tests with extension Ftetwild
PiperOrigin-RevId: 631776421
Change-Id: I66f6b4058b86338a10d06c39bc93bef1c6fbdab6
Now we can load flex with format 2.2 binary and ASCII.
There are two different parsing strategies. One for gmsh app and the other is for ftetwild.
Used the shark model from Scanned Objects by Google Research:
https://app.gazebosim.org/GoogleResearch/fuel/models/Weisshai_Great_White_Shark
PiperOrigin-RevId: 619229499
Change-Id: I6eb876afcbc8a00631914b093c45bde10c0caaf6
Alessio Quaglino