feat(assets): local_jar_lid — the operator's own printed screw jar

.gitattributes

@@ -889,3 +889,4 @@ assets/articulated/artvip/microwave_3/usd/model.usd filter=lfs diff=lfs merge=lf
 assets/articulated/artvip/rice_cooker_3/usd/model.usd filter=lfs diff=lfs merge=lfs -text
 assets/articulated/artvip/rice_cooker_7/usd/model.usd filter=lfs diff=lfs merge=lfs -text
 assets/articulated/artvip/scissors_22/usd/model.usd filter=lfs diff=lfs merge=lfs -text
+assets/local_jar_lid/Jar__Lid_source.stl filter=lfs diff=lfs merge=lfs -text

assets/local_jar_lid/Jar__Lid_source.stl

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+version https://git-lfs.github.com/spec/v1
+oid sha256:122c103674a6e61fe04bc0a48f5fd078747b3d3a2610b029aac97a8528963391
+size 628284

assets/local_jar_lid/README.md

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+# local_jar_lid — the operator's own 3D-printed screw jar
+
+Project-authored screw asset (the `local_bottle_cap` / `local_juice_shot`
+family), built from the operator's own print plate `Jar__Lid_source.stl`
+(both parts on one plate, mm units).
+
+## Provenance / reproduction
+
+- `Jar__Lid_source.stl` — the original upload, unmodified (12 564 triangles,
+  body at x ∈ [−45, 45], lid at x ∈ [77, 168] on the plate).
+- Split by triangle-centroid x < 60 mm, each part recentred (xy on its AABB
+  centre, base at z = 0) and scaled mm → m into `jar_body_vis.obj` /
+  `jar_lid_vis.obj` (visual-only meshes; collision in the MJCF is procedural).
+- **The thread is MEASURED from this mesh, not guessed**: fitting the helix
+  through the lid's inner-skirt crest vertices and the neck's outer crest
+  vertices independently, both converge on a **3-start thread, lead
+  13.35 mm/turn** (phase concentration 0.73 / 0.65). Engagement spans ~7.5 mm
+  of skirt ⇒ the real lid disengages in ~0.56 turn.
+- Geometry: body 90 × 90 × ~110 mm chamfered square + Ø77.4 × 11 mm neck
+  (total 121.83 mm); lid 90 × 90 × 33 mm, 15 mm skirt, 0.6 mm diametral
+  clearance.
+
+## Mechanism (`jar_lid.xml`)
+
+`lid_slide` (prismatic, FIRST joint — parrot_sim overlay contract) +
+`lid_twist` (coaxial hinge) coupled by a joint equality at the measured lead
+(`polycoef[1] = 0.01335 / 2π`). Dry thread friction 0.055 N·m + 5 N skirt
+friction (both `solreffriction`-stiffened) ⇒ straight-pull threshold ≈ 31 N;
+`<contact><exclude>` between lid and jar (the equality IS the thread).
+
+**ESTIMATED, pending measurement**: part masses (PLA; authored 0.20 kg jar /
+0.08 kg lid). Weigh the real print and correct.
+
+## USD
+
+`usd/jar_lid_render.usda` — render-grade conversion via
+`RoboVerse/scripts/mjcf_screwcap_to_usd.py`; the screw ratio rides the
+prismatic joint as `wuji:screwPitchMPerRad` customData (UsdPhysics has no
+screw-coupling schema; wiring a PhysX mimic drive is the Isaac-side follow-up).
+
+## Consumers
+
+- task `hand_track.open_jar_lid`
+  (`RoboVerse/roboverse_pack/tasks/hand_track/hand_track_open_jar_lid.py`)
+- physics regressions
+  `RoboVerse/roboverse_pack/tasks/hand_track/tests/test_jar_lid_asset.py` (8)

assets/local_jar_lid/jar_lid.xml

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+<mujoco model="jar_lid">
+  <!--
+    3D-printed square storage jar with a screw lid, built from the user's own
+    print (Jar__Lid.stl, one plate with both parts side by side; split, recentered
+    xy-on-centre / base-at-z=0, mm units -> scale 0.001).
+
+    THE THREAD IS MEASURED FROM THE MESH, not guessed (the open_juice_shot lesson:
+    model the LEAD, not the ridge pitch). Fitting the helix through the lid's
+    inner-skirt crest vertices and the neck's outer crest vertices independently:
+    both converge on a 3-START thread, joint best fit LEAD = 13.35 mm/turn
+    (phase concentration 0.73 / 0.65 on a 12.5k-triangle mesh). Thread engagement
+    spans ~7.5 mm of the skirt, so the real lid disengages in ~0.56 turn - inside
+    the one-wrist-rotation regime open_juice_shot proved collectable (its v1, at
+    1.67 turns, failed 22 consecutive real takes).
+
+    Measured geometry: body 90 x 90 x ~110 mm square (chamfered corners, max
+    half-diagonal 61.15 mm), neck OD 77.4 mm x ~11 mm tall on top (total jar
+    121.83 mm); lid 90 x 90 x 33 mm with a 15 mm-deep skirt, thread crests at
+    inner r ~38.1 mm (0.6 mm diametral clearance to the neck).
+
+    Mechanism (the local_bottle_cap v2 design): the lid rides a vertical slide
+    (lid_slide, FIRST joint on the body - parrot_sim's articulation_joint_frames
+    takes the first joint, and the overlay must draw the slide-travel gate) plus a
+    coaxial hinge (lid_twist), tied by a joint equality at the measured lead
+    (polycoef[1] = 0.01335 / 2pi = 0.00212473 m/rad). Dry friction on the twist
+    joint makes a straight pull back-drive the screw: F_pull = 2pi*frictionloss /
+    lead = 2pi*0.055/0.01335 ~ 25.9 N, ~9.4x the 0.28 kg assembly's weight, so a
+    yank lifts the whole jar instead of opening it. Breakaway torque 0.055 N*m is
+    ~11x under the torque a priority-2 grip delivers at the lid's 45 mm half-width
+    - the cure for "hard to turn" is grip friction, never a weaker thread.
+    The huge slide armature is the screw's reflected inertia, I_twist/lead_rad^2
+    ~ 1.1e-4 / (0.00212473^2) ~ 24 kg-eq. The equality's near-rigid solimp is the
+    juice_shot elastic-leak fix (a soft equality let a 20 N pull deflect 3.2 mm
+    WITHOUT the thread slipping). lid<->jar contacts are excluded: the equality IS
+    the thread, and MuJoCo's automatic parent-child filter is skipped when the
+    parent is welded to the world, i.e. exactly in fixed-base standalone loads
+    like the asset tests.
+
+    ESTIMATED (not measured): masses - PLA print, jar 0.20 kg / lid 0.08 kg;
+    weigh the real parts and correct. The closed lid sits at z = 110 mm (its
+    skirt over the neck, resting at the square body's top edge).
+
+    Collision is procedural (box body + cylinder neck; box lid), matching the
+    board_nail / bottle_cap philosophy; visuals are the real print meshes. The
+    box corners overstate the chamfered print by ~2.5 mm at the diagonals.
+  -->
+  <compiler angle="radian" meshdir="."/>
+  <asset>
+    <mesh name="jar_body_mesh" file="jar_body_vis.obj"/>
+    <mesh name="jar_lid_mesh" file="jar_lid_vis.obj"/>
+  </asset>
+  <worldbody>
+    <body name="jar">
+      <geom name="jar_visual" type="mesh" mesh="jar_body_mesh" group="2"
+            contype="0" conaffinity="0" density="0" rgba="0.96 0.95 0.92 1"/>
+      <!-- square body: 90 x 90 x 110 mm; grasp-priority friction (family value) -->
+      <geom name="jar_body_col" type="box" size="0.045 0.045 0.055" pos="0 0 0.055"
+            mass="0.20" friction="3.0 0.15 0.01" priority="2" rgba="0 1 0 0" group="3"/>
+      <!-- neck: OD 77.4 x 11 mm, z 110..121 -->
+      <geom name="jar_neck_col" type="cylinder" size="0.0387 0.0055" pos="0 0 0.1155"
+            mass="0.0" friction="3.0 0.15 0.01" priority="2" rgba="0 1 0 0" group="3"/>
+      <body name="lid" pos="0 0 0.110">
+        <!-- slide FIRST (overlay contract), then the coaxial twist -->
+        <!-- The slide carries its own dry friction: the 15 mm skirt rides the neck
+             with 0.6 mm diametral clearance, and that rubbing is real. It also
+             closes the last elastic leak: 20 N of pull reached the twist friction
+             only THROUGH the equality, whose regularization let 3.4 mm creep
+             past; 5 N of slide friction (with the same stiff solreffriction)
+             holds the direct path shut. Total pull threshold ~ 25.9 + 5 = 31 N. -->
+        <joint name="lid_slide" type="slide" axis="0 0 1" range="0 0.045"
+               armature="24" damping="0.5" frictionloss="5.0" solreffriction="0.004 1"/>
+        <!-- solreffriction stiffens the dry-friction CONSTRAINT itself: with the
+             default-soft value a constant load creeps through it regardless of the
+             frictionloss magnitude (measured here: a 20 N pull walked the slide
+             4.9 mm in 3 s) - the hammer_insert_nail sag fix. -->
+        <joint name="lid_twist" type="hinge" axis="0 0 1" range="0 21.2"
+               frictionloss="0.055" damping="0.02" solreffriction="0.004 1"/>
+        <geom name="lid_visual" type="mesh" mesh="jar_lid_mesh" group="2"
+              contype="0" conaffinity="0" density="0" rgba="0.97 0.96 0.93 1"/>
+        <geom name="lid_col" type="box" size="0.045 0.045 0.0165" pos="0 0 0.0165"
+              mass="0.08" friction="3.0 0.15 0.01" priority="2" rgba="0 1 0 0" group="3"/>
+      </body>
+    </body>
+  </worldbody>
+  <equality>
+    <!-- slide = lead/(2pi) * twist ; lead = 13.35 mm/turn, 3-start, MEASURED -->
+    <joint joint1="lid_slide" joint2="lid_twist" polycoef="0 0.00212473 0 0 0"
+           solref="0.002 1" solimp="0.999 0.9999 0.00001 0.5 2"/>
+  </equality>
+  <contact>
+    <exclude body1="jar" body2="lid"/>
+  </contact>
+</mujoco>