These fields (`flg_gravcomp` and `flg_surfacevel`) replace the fast-path checks originally guarded by `ngravcomp` and (recently) `nsurfacevel`. Since the engine uses these integers only as flags (zero vs non-zero), migrating them to actual booleans makes them writeable from the Python bindings at runtime without violating size/dimension constraints.
The legacy integer field `ngravcomp` is marked as deprecated and will be removed in a future release.
PiperOrigin-RevId: 949779204
Change-Id: Ifab1f026063a4239302e6ad689663b611b59dda8
https://www.youtube.com/watch?v=PdSdrqhSiZA
The new geom attribute surfacevel (6 numbers: linear and angular velocity in the geom's local frame, angular about the geom frame origin) specifies the velocity of the geom's surface material relative to the geom frame. The relative surface velocity of the two geoms is added to the tangential contact rows of efc_vel in mj_referenceConstraint, so friction drives touching bodies toward the motion of the surface: objects on a conveyor are transported at belt speed, turntables impart omega x r with torsional spin-up for condim >= 4, and surface velocities compose with each other and with body motion. The component along the contact normal is projected out: probe experiments showed that velocity-space emission chatters mass-independently and ingestion merely deepens penetration; normal-direction effects belong to force-space features.
surfacevel is interpreted in the geom frame as authored: for mesh geoms, whose compiled frame absorbs the mesh centering and principal-axes transform, the compiler re-expresses the authored value in the compiled frame.
No special interaction with sleeping: objects being transported do not fall asleep because they are moving; objects at rest on an active surface may sleep like any other resting object.
Includes showcase models (model/surfacevel/): a luggage carousel whose ring is a spinning square-profile supertorus fed by a cascade of belts with matched spinning end rollers, bags dropping in and circulating indefinitely; and a treadmill with a passive humanoid.
PiperOrigin-RevId: 948647785
Change-Id: I0c6559a91cc7ece1237eb8ac2e51986e7342d962
The primal cost has curvature of at least M in every zone, making it strongly
convex in the M-norm and bounding the suboptimality of any point by the
Fenchel duality gap at its constraint forces:
cost(qacc) - cost* <= 0.5*grad'*M^-1*grad
Since M's factorization always exists, this certificate is evaluable before
the solver does any work: one triangular solve and one dot product. When the
warmstarted solution is already certified to satisfy the tolerance, CG and
Newton now return with zero iterations; for Newton this skips building and
factorizing the Hessian. If the certificate declines, Newton gets a second
exit after factorization: the Newton decrement, checked before the first
line search.
Because the gap bounds cost suboptimality, stiff constraints can convert it
into force errors of order sqrt(2*gap*stiffness). Newton solutions are
characteristically force-accurate, so Newton zero-iteration exits also
require the gradient criterion, preserving constraint-force accuracy at
rest; CG solutions are characteristically cost-accurate and exit on the gap
alone.
On a settling pile of 50 boxes (300 dofs, ~200 contacts), end-to-end time
per step drops 13% over a settle-then-rest run and 27% in the quiescent
limit, with Newton iterations falling from 0.98 to 0.40 per step.
Tests: WarmstartZeroIterations sweeps solver/cone/jacobian on a settled box,
asserting zero iterations, forward/inverse consistency, and agreement with a
tolerance=0 control solve from the same state. WarmstartZeroIterationsIslands
checks per-island exits with a kicked box next to a settled one.
RefsiteConservesMomentum now requests an exact solve (tolerance=0), since it
asserts momentum conservation tighter than the solver tolerance contract.
PiperOrigin-RevId: 947993735
Change-Id: I2fd855774bff619709b2c386f1ba2714286e0821
Yuval Tassa