Implement multi-cell finite element method for interpolated flexes.

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 commit is contained in:
Alessio Quaglino
2026-04-17 04:10:54 -07:00
committed by Copybara-Service
parent 8415dff307
commit 6c7ed66781
36 changed files with 1777 additions and 1039 deletions
+9
View File
@@ -2,6 +2,15 @@
Changelog
=========
Upcoming version (not yet released)
-----------------------------------
General
^^^^^^^
- Added :ref:`multi-cell support<body-flexcomp-cellnum>` for trilinear and quadratic flexes. Note that the implicit
integrator uses a dense solver for the flex degrees of freedom, which can be slow for multi-cell flexes.
Version 3.7.0 (April 14, 2026)
------------------------------