Coupling with VBD and XPBD

Steel can own the rigid bodies and articulations of a scene inside Newton’s experimental coupled solvers, next to SolverVBD or SolverXPBD for cloth, cables and soft bodies. Build Steel on a ModelView of the rigid part; a Steel entry that owns particles raises.

• Steel consumes coupling forces through state.body_f and reports articulated effective mass from the endpoint mobility $J\tilde H^{-1}J^\top$ at model.joint_q. The effective mass is evaluated on the host, so issue the body, inertial and joint notifications it names outside capture.
• When the coupler runs more than one iteration, Steel saves its friction-patch history on the first solve of a step and restores it on each restart, so repeated solves start from the same history.
• Raised inside a coupler: sleeping, contact warm start, contact compliance, contact torsion, RUN_TO_RUN, and update_mass_matrix_interval above 1 with more than one coupler iteration. Steel cannot be a proxy destination.
• Coupled use is validated with solve_mode="serial" and the immediate response. Set model.rigid_contact_max to the coupled contact buffer’s capacity before constructing the coupled solver.

Figure 13Who owns what in a coupled step. Steel never owns particles; the coupler exchanges contacts and forces with the deformable solver every coupled iteration. Tutorial: Coupling Steel with XPBD cloth

Proxy coupling is tuning-sensitive; treat coupled scenes as experiments and check them with focused metrics.