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
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
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
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 `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
The flex-SDF algorithm uses the same logic as mesh-SDF. Previous to this change, the flex was instead colliding with the convex hull of the mesh generated automatically with marching cubes from the SDF.
PiperOrigin-RevId: 876420302
Change-Id: I3bf6552b6b8e108ba4c4209bbcf10fe5f2b2fd90
This CL rolls back the change from changelist 794576123 since the previous version was more robust and stable. Compared to the original algorithm, this changes handles degenerate and very large triangles as well.
BEGIN_PUBLIC
Restore mesh-SDF collisions.
END_PUBIC
PiperOrigin-RevId: 875716983
Change-Id: If0de41dc7bbd60460779821d2338cf2d661f40d5
Temporary changes to the octree:
- Changed frame from mesh to geom
Before change (tolerance 1e-3):
```
Simulation time : 2.34 s
Steps per second : 4275
Realtime factor : 8.55 x
Time per step : 233.9 µs
Newton iters / step : 2.26
Contacts / step : 3.69
Constraints / step : 14.76
Degrees of freedom : 12
Dynamic memory usage : 0.7% of 14M
```
After change (6 octree levels):
```
Simulation time : 2.24 s
Steps per second : 4472
Realtime factor : 8.94 x
Time per step : 223.6 µs
Newton iters / step : 2.47
Contacts / step : 3.37
Constraints / step : 13.49
Degrees of freedom : 12
Dynamic memory usage : 0.2% of 14M
```
PiperOrigin-RevId: 781019754
Change-Id: Ib15581244dfe9e571e1c6c2cac4a101cf3d8ba3d
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
Add pulley example to show a circle use case.
Switch on flex edge rendering by default (no effect when flex skin is rendered).
PiperOrigin-RevId: 700738379
Change-Id: I8469bbf194de01c8dab66c9a51c49879013df141
Also, fix a bug with Flex textures that was causing an incorrect allocation of the textures in mjModel. Fixes#2013.
PiperOrigin-RevId: 692510858
Change-Id: If781716216974e085244da27bc3aa57d91c3458c
Improve the model's rendering FPS by reducing the number of shadow-casting lights from 7 to 2.
https://youtu.be/e8lUuykQPGs
PiperOrigin-RevId: 686118052
Change-Id: If376564fdc23ad8d754dac1e5825079c0b806063
Support actdim attribute on plugin actuators.
Remove the actuator_actdim callback. This callback leads to crashes when loading keyframes for models that have a stateful plugin.
PiperOrigin-RevId: 650649505
Change-Id: I40d1994d02ae4e20ce631b2702a984766cf2628e
Alessio Quaglino