{
  "catalog_id": 20,
  "title": "Eastbound sidewalk chase with backpack retrieval",
  "source_template": "wheelchair",
  "summary": "Four children play-chase east along the south sidewalk. The trailing child notices a previously dropped backpack, turns back, retrieves it, and walks east to rejoin the waiting group. Nobody enters the roadway.",
  "focus_xy": [
    40,
    -6.2
  ],
  "initial_review_time_s": 9,
  "ego_stop_x_m": 14,
  "ego_release_s": 33,
  "events": [
    {
      "time_s": -7,
      "label": "Four children run east; the dropped backpack remains behind on the sidewalk."
    },
    {
      "time_s": 0,
      "label": "The trailing child notices the missing backpack and stops."
    },
    {
      "time_s": 2,
      "label": "The child completes an in-place turn and runs back west."
    },
    {
      "time_s": 9,
      "label": "The returning child crouches beside the backpack while the others wait farther east."
    },
    {
      "time_s": 11,
      "label": "The backpack is lifted and secured in a forward hand grip."
    },
    {
      "time_s": 13,
      "label": "The child finishes turning east and walks back carrying the backpack."
    },
    {
      "time_s": 31,
      "label": "The child rejoins the group and all four continue east."
    },
    {
      "time_s": 33,
      "label": "Ego may resume after confirming that the reunited group remains on the sidewalk."
    },
    {
      "time_s": 40,
      "label": "All four children remain present, walking east with the recovered backpack."
    }
  ],
  "actors": [
    {
      "id": "c020_a",
      "label": "Child 1: play-chase leader",
      "kind": "child",
      "role": "Eastbound leader who pauses for the backpack retriever.",
      "color": "blue",
      "length_m": 0.36,
      "width_m": 0.36,
      "height_m": 1.42,
      "keys": [
        {
          "t": -7,
          "x": 38,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 0,
          "x": 54,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 4,
          "x": 62.2,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 5,
          "x": 63,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "stand"
        },
        {
          "t": 31,
          "x": 63,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 34,
          "x": 66.9,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 40,
          "x": 75.3,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        }
      ],
      "attach_to": "",
      "attach_start_s": -7,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0,
        0,
        0
      ],
      "interaction": "Leads the playful chase without contact, slows on the sidewalk, waits for the returning child, then resumes walking east."
    },
    {
      "id": "c020_b",
      "label": "Child 2: inner-sidewalk pursuer",
      "kind": "child",
      "role": "Playful pursuer maintaining a staggered position behind the leader.",
      "color": "yellow",
      "length_m": 0.35,
      "width_m": 0.35,
      "height_m": 1.3,
      "keys": [
        {
          "t": -7,
          "x": 35.5,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 0,
          "x": 51.5,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 4,
          "x": 59.7,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 5,
          "x": 60.5,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "stand"
        },
        {
          "t": 31,
          "x": 60.5,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 34,
          "x": 64.4,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 40,
          "x": 72.8,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        }
      ],
      "attach_to": "",
      "attach_start_s": -7,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0,
        0,
        0
      ],
      "interaction": "Follows the leader in a separate sidewalk track and waits without blocking the returning child's route."
    },
    {
      "id": "c020_c",
      "label": "Child 3: trailing playmate",
      "kind": "child",
      "role": "Third member of the eastbound play-chase group.",
      "color": "teal",
      "length_m": 0.34,
      "width_m": 0.34,
      "height_m": 1.25,
      "keys": [
        {
          "t": -7,
          "x": 33,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 0,
          "x": 49,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 4,
          "x": 57.2,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 5,
          "x": 58,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "stand"
        },
        {
          "t": 31,
          "x": 58,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 34,
          "x": 61.9,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        },
        {
          "t": 40,
          "x": 70.3,
          "y": -5.45,
          "z": 0,
          "heading_deg": 0,
          "pose": "walk"
        }
      ],
      "attach_to": "",
      "attach_start_s": -7,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0,
        0,
        0
      ],
      "interaction": "Keeps a clear longitudinal gap during play and leaves the adjacent sidewalk track available for the backpack owner's return."
    },
    {
      "id": "c020_d",
      "label": "Child 4: backpack owner and retriever",
      "kind": "child",
      "role": "Initially follows the group, notices the dropped backpack, retrieves it, and rejoins.",
      "color": "orange",
      "length_m": 0.36,
      "width_m": 0.36,
      "height_m": 1.35,
      "keys": [
        {
          "t": -7,
          "x": 30,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "run"
        },
        {
          "t": 0,
          "x": 44,
          "y": -6.85,
          "z": 0,
          "heading_deg": 0,
          "pose": "stand"
        },
        {
          "t": 2,
          "x": 44,
          "y": -6.85,
          "z": 0,
          "heading_deg": 180,
          "pose": "run"
        },
        {
          "t": 9,
          "x": 27.42,
          "y": -6.85,
          "z": 0,
          "heading_deg": 180,
          "pose": "crouch"
        },
        {
          "t": 11,
          "x": 27.42,
          "y": -6.85,
          "z": 0,
          "heading_deg": 180,
          "pose": "carry"
        },
        {
          "t": 13,
          "x": 27.42,
          "y": -6.85,
          "z": 0,
          "heading_deg": 360,
          "pose": "carry"
        },
        {
          "t": 31,
          "x": 56.22,
          "y": -6.85,
          "z": 0,
          "heading_deg": 360,
          "pose": "carry"
        },
        {
          "t": 34,
          "x": 60.12,
          "y": -6.85,
          "z": 0,
          "heading_deg": 360,
          "pose": "carry"
        },
        {
          "t": 40,
          "x": 68.52,
          "y": -6.85,
          "z": 0,
          "heading_deg": 360,
          "pose": "carry"
        }
      ],
      "attach_to": "",
      "attach_start_s": -7,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0,
        0,
        0
      ],
      "interaction": "Stops before both reversals. At 9 seconds, crouches with hands reaching west toward the backpack. Lifts it through 11 seconds, turns in place while retaining the grip, then walks east at approximately 1.6 m/s to rejoin. Carry poses retain the forward hand grip during walking."
    },
    {
      "id": "c020_bag",
      "label": "Dropped backpack: recovered by Child 4",
      "kind": "backpack",
      "role": "Single persistent dropped and subsequently carried backpack.",
      "color": "red",
      "length_m": 0.22,
      "width_m": 0.3,
      "height_m": 0.38,
      "keys": [
        {
          "t": -7,
          "x": 27,
          "y": -6.85,
          "z": 0,
          "heading_deg": 180,
          "pose": "stand"
        },
        {
          "t": 0,
          "x": 27,
          "y": -6.85,
          "z": 0,
          "heading_deg": 180,
          "pose": "stand"
        },
        {
          "t": 9,
          "x": 27,
          "y": -6.85,
          "z": 0,
          "heading_deg": 180,
          "pose": "stand"
        },
        {
          "t": 11,
          "x": 27,
          "y": -6.85,
          "z": 0.646437,
          "heading_deg": 180,
          "pose": "carry"
        },
        {
          "t": 13,
          "x": 27.84,
          "y": -6.85,
          "z": 0.653563,
          "heading_deg": 360,
          "pose": "carry"
        },
        {
          "t": 31,
          "x": 56.64,
          "y": -6.85,
          "z": 0.653563,
          "heading_deg": 360,
          "pose": "carry"
        },
        {
          "t": 34,
          "x": 60.54,
          "y": -6.85,
          "z": 0.653563,
          "heading_deg": 360,
          "pose": "carry"
        },
        {
          "t": 40,
          "x": 68.94,
          "y": -6.85,
          "z": 0.653563,
          "heading_deg": 360,
          "pose": "carry"
        }
      ],
      "attach_to": "c020_d",
      "attach_start_s": 11,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0.42,
        0,
        0.65
      ],
      "interaction": "Rests on the sidewalk until pickup. Its support root rises continuously from 9 to 11 seconds. Attachment begins at the matching lifted position; thereafter it sweeps with the child's body during the turn and remains gripped ahead of the torso."
    }
  ],
  "acceptance_checks": [
    "Require exactly four child actors and one backpack, all persistent from -7 through 40 seconds.",
    "At every 20 Hz sample, keep all child and backpack footprints inside the supplied south sidewalk polygon; do not add a roadway crossing.",
    "Maintain at least 0.6 m body clearance between ordinary walkers, including during reunion and group restart.",
    "Check running cruise speeds of 2 to 4 m/s, walking cruise speeds of 0.6 to 1.7 m/s, bounded acceleration, and zero translation during the two stationary turns.",
    "Require continuous backpack pickup and attachment at 11 seconds, with no duplicate backpack, ground penetration, or snapping during its attached turn.",
    "Ego must stop at x=14 and may resume at 33 seconds only after confirming that its complete swept corridor remains clear.",
    "Human review must approve the full rehearsal, geometry, separation, and original-photo placement before any image generation; these checks are requirements, not reported test results."
  ],
  "assumptions": [
    "Image 1 and the wheelchair map support the broad street, sidewalk, and building context only. All children, motions, coordinates, timing, and backpack placement are counterfactual proposals.",
    "The unspecified group is instantiated as four children. The backpack was dropped before -7 seconds and is not noticed until 0 seconds; no unshown disappearance or second backpack is implied.",
    "The selected south sidewalk tracks at y=-5.45 and y=-6.85 lie within the supplied polygons over the authored route.",
    "Playback is finite and non-looping: -7 through 40 seconds at 20 Hz, including both endpoints, for 941 samples. Use bounded-speed interpolation with explicit stationary turns and no positional overshoot.",
    "All human roots use z=0 on the mapped support surface. Attached backpack z samples account for the supplied ground-plane slope; attachment transforms take precedence during the attachment interval.",
    "Ego is implicit rather than a duplicate cast actor. It approaches on y=0 from x=13 at -7 seconds, brakes from 2 m/s to rest at x=14 by -6 seconds, and after release accelerates at no more than 0.75 m/s squared to at most 1.5 m/s.",
    "Exact static-obstacle footprints are not supplied and require human confirmation. A later Image 2.5 edit must use original Image 1, with this rehearsal supplying positions and postures only; no image generation is authorized by this annotation."
  ]
}