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MuJoCo 3.9 redesigned contact margin/gap. Detection moved from `dist < margin` to `dist < margin + gap`, and force generation from `dist < margin - gap` to `dist < margin`. All five suction sites here use margin == gap, the idiom for "detect early but only apply force on true contact". Under the new semantics that same markup generates force from a full margin away, so the cups push parts off before touching them. Measured with margin = gap = 0.02: on 3.6 a 15 mm separation is detected with no force, on 3.10 it is force-generating. Applies the upstream migration, margin_new = margin_old - gap_old, which is 0 at every site since margin equals gap. This is the same markup upstream migrated its own adhesion demo to. Ordering: this markup only behaves correctly on MuJoCo 3.10 or newer. Under 3.6 it reads as detection at 0 and force at -gap, so the cups stop sensing parts until they interpenetrate. Merge this only once moveit_pro ships the 3.10 bump, which also carries the widen_body_margin_for_gap change that restores detection on multi-geom bodies. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012DpJinnRQknbm62X7GCveK
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Motivation
MuJoCo 3.9 redesigned the contact
marginandgapgeom attributes, and every suction site here still uses the pre-3.9 idiom. PickNikRobotics/moveit_pro#22404 takes the bundled runtime to 3.13.0, past that change.Brief description
Detection moved from
dist < margintodist < margin + gap, and force fromdist < margin - gaptodist < margin. All five sites usemargin == gap, the idiom for sensing a part without pushing it away, which under the new semantics generates force from a full margin out.Applies the upstream migration
margin_new = margin_old - gap_old, zero at every site, withgapunchanged.factory_sim'soverride="enable"forces every margin too_margin, so its edits are inert there; kept for consistency.Merge order
Correct only against the 3.13.0 runtime that PR brings in. Under the 3.6 shipping today this reads as detection at
0, so cups stop sensing parts until they interpenetrate.How it was tested
Separation sweep against a multi-geom target, stepping 10 µm, reading the outermost separation that registers a contact and the outermost that registers a force-generating one. Single-geom pairs skip MuJoCo's midphase, so the target carries five geoms.
3.13.0 with these edits reproduces 3.6.0 exactly at both site sizes. Without them the cup generates force from a full margin out, which is the suction cup pushing the part away before it touches.
Every scene in the affected packages that loads standalone compiles on 3.13.0:
factory_sim/description/scene.xml(179 geoms),hangar_sim/description/hangar_scene.xml(306), andhangar_sim/description/ur5e_ridgeback.xml(76).hangar_sim/description/hangar.xmlis an include fragment and does not load standalone on 3.6.0 either. All five migrated geoms compile tomargin = 0withgapintact, detection atgapand force at contact.The 3.10 pairing also needed a
body_marginworkaround alongside these edits: MuJoCo 3.9 and 3.10 computebody_marginwithout gap, culling multi-geom bodies at the midphase before the leaves that would detect them, which is the shape every site here migrates to. Measured on 3.10 these geoms givebody_margin = 0and detection collapses to contact. Upstream folded gap intobody_marginin 3.11.0, so on 3.13 every migrated body reportsbody_margin = margin + gapand no workaround is needed.Release notes
None. The user-facing migration guidance ships with PickNikRobotics/moveit_pro#22404.