{
  "catalog_id": 12,
  "title": "Two scooters and a backward pickup",
  "source_template": "wheelchair",
  "summary": "Two children cross on kick scooters. One continues while the other stops, looks back and retrieves a dropped toy box.",
  "focus_xy": [
    33.4,
    0.2
  ],
  "initial_review_time_s": 4.4,
  "ego_stop_x_m": 12,
  "ego_release_s": 16,
  "events": [
    {
      "time_s": -7,
      "label": "Two child riders approach the south curb; one small toy box already lies in the road."
    },
    {
      "time_s": -3,
      "label": "Both children begin riding north across the roadway."
    },
    {
      "time_s": 0,
      "label": "The trailing child looks back and brakes while the other continues forward."
    },
    {
      "time_s": 3,
      "label": "The stopped child finishes a manual scooter pivot toward the dropped box."
    },
    {
      "time_s": 4.4,
      "label": "The returning child crouches beside the box within the ego corridor."
    },
    {
      "time_s": 6,
      "label": "The box is lifted into the child's hand; the other child waits on the north sidewalk."
    },
    {
      "time_s": 14,
      "label": "The returning child reaches the north sidewalk with the recovered box."
    },
    {
      "time_s": 16,
      "label": "After both children remain clear, ego may resume subject to the clearance check."
    },
    {
      "time_s": 40,
      "label": "Both children and scooters remain on the north sidewalk; the recovered box stays held."
    }
  ],
  "actors": [
    {
      "id": "c012_return",
      "label": "Child A returning for the toy",
      "kind": "scooter",
      "role": "One 1.30 m child and one lightweight kick scooter with a 0.04 m deck; a single composite actor including its rider",
      "color": "orange",
      "length_m": 1.02,
      "width_m": 0.78,
      "height_m": 1.34,
      "keys": [
        {
          "t": -7,
          "x": 33.4,
          "y": -6.7,
          "z": 0,
          "heading_deg": 90,
          "pose": "push"
        },
        {
          "t": -3,
          "x": 33.4,
          "y": -4.2,
          "z": 0,
          "heading_deg": 90,
          "pose": "handlebar"
        },
        {
          "t": 0,
          "x": 33.4,
          "y": 1,
          "z": 0,
          "heading_deg": 90,
          "pose": "handlebar"
        },
        {
          "t": 1,
          "x": 33.4,
          "y": 1.45,
          "z": 0,
          "heading_deg": 90,
          "pose": "stand"
        },
        {
          "t": 3,
          "x": 33.4,
          "y": 1.45,
          "z": 0,
          "heading_deg": 270,
          "pose": "push"
        },
        {
          "t": 4.4,
          "x": 33.4,
          "y": 0.2,
          "z": 0,
          "heading_deg": 270,
          "pose": "crouch"
        },
        {
          "t": 6,
          "x": 33.4,
          "y": 0.2,
          "z": 0,
          "heading_deg": 270,
          "pose": "reach"
        },
        {
          "t": 8.5,
          "x": 33.4,
          "y": 0.2,
          "z": 0,
          "heading_deg": 450,
          "pose": "handlebar"
        },
        {
          "t": 14,
          "x": 33.4,
          "y": 6.65,
          "z": 0,
          "heading_deg": 450,
          "pose": "stand"
        },
        {
          "t": 40,
          "x": 33.4,
          "y": 6.65,
          "z": 0,
          "heading_deg": 450,
          "pose": "stand"
        }
      ],
      "attach_to": "",
      "attach_start_s": -7,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0,
        0,
        0
      ],
      "interaction": "Turns the head back while braking at 0 s, stops by 1 s, and dismounts within the same composite rig. During 1..3 s the child plants the feet and hand-pivots the light scooter, rather than performing a powered zero-radius turn. Walks it south, crouches with the box ahead-left, grips it at 5.3 s and lifts it by 6 s. Manually pivots north during 6..8.5 s, then rides slowly with the box in the left hand and the right hand on the handlebar. Hand-walks the scooter across curb transitions. No additional child mesh appears."
    },
    {
      "id": "c012_forward",
      "label": "Child B continuing across",
      "kind": "scooter",
      "role": "One 1.39 m child and one lightweight kick scooter with a 0.04 m deck; a single composite actor including its rider",
      "color": "blue",
      "length_m": 1.08,
      "width_m": 0.58,
      "height_m": 1.43,
      "keys": [
        {
          "t": -7,
          "x": 36.3,
          "y": -6.4,
          "z": 0,
          "heading_deg": 90,
          "pose": "push"
        },
        {
          "t": -3,
          "x": 36.3,
          "y": -3.6,
          "z": 0,
          "heading_deg": 90,
          "pose": "handlebar"
        },
        {
          "t": 0,
          "x": 36.3,
          "y": 1.7,
          "z": 0,
          "heading_deg": 90,
          "pose": "handlebar"
        },
        {
          "t": 3,
          "x": 36.3,
          "y": 5.3,
          "z": 0,
          "heading_deg": 90,
          "pose": "push"
        },
        {
          "t": 5,
          "x": 36.3,
          "y": 6.65,
          "z": 0,
          "heading_deg": 90,
          "pose": "stand"
        },
        {
          "t": 8.5,
          "x": 36.3,
          "y": 6.65,
          "z": 0,
          "heading_deg": 90,
          "pose": "stand"
        },
        {
          "t": 14,
          "x": 36.3,
          "y": 6.65,
          "z": 0,
          "heading_deg": 90,
          "pose": "stand"
        },
        {
          "t": 40,
          "x": 36.3,
          "y": 6.65,
          "z": 0,
          "heading_deg": 90,
          "pose": "stand"
        }
      ],
      "attach_to": "",
      "attach_start_s": -7,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0,
        0,
        0
      ],
      "interaction": "Continues north without reversing or joining the pickup. Keeps hands on the handlebar while riding, then steps off within the composite to hand-walk across the north curb. Waits with both feet grounded and the scooter retained beside the body."
    },
    {
      "id": "c012_toy",
      "label": "Dropped toy box",
      "kind": "box",
      "role": "The single small object retrieved by Child A",
      "color": "yellow",
      "length_m": 0.14,
      "width_m": 0.1,
      "height_m": 0.09,
      "keys": [
        {
          "t": -7,
          "x": 33.75,
          "y": -0.2,
          "z": 0,
          "heading_deg": 270,
          "pose": "stand"
        },
        {
          "t": 0,
          "x": 33.75,
          "y": -0.2,
          "z": 0,
          "heading_deg": 270,
          "pose": "stand"
        },
        {
          "t": 4.4,
          "x": 33.75,
          "y": -0.2,
          "z": 0,
          "heading_deg": 270,
          "pose": "stand"
        },
        {
          "t": 5.3,
          "x": 33.75,
          "y": -0.2,
          "z": 0,
          "heading_deg": 270,
          "pose": "reach"
        },
        {
          "t": 6,
          "x": 33.75,
          "y": -0.2,
          "z": 0.647783,
          "heading_deg": 270,
          "pose": "carry"
        },
        {
          "t": 8.5,
          "x": 33.05,
          "y": 0.6,
          "z": 0.652217,
          "heading_deg": 450,
          "pose": "carry"
        },
        {
          "t": 14,
          "x": 33.05,
          "y": 7.05,
          "z": 0.652217,
          "heading_deg": 450,
          "pose": "carry"
        },
        {
          "t": 40,
          "x": 33.05,
          "y": 7.05,
          "z": 0.652217,
          "heading_deg": 450,
          "pose": "carry"
        }
      ],
      "attach_to": "c012_return",
      "attach_start_s": 6,
      "attach_end_s": 40,
      "attach_offset_xyz": [
        0.4,
        0.35,
        0.65
      ],
      "interaction": "Remains on the asphalt until hand contact at 5.3 s, then rises continuously to the attachment transform at 6 s. The child grips the small box with the left palm beneath it. Its lateral offset keeps it outside the approaching scooter wheel track. After attachment it follows the child through the manual turn and remains held through 40 s."
    }
  ],
  "acceptance_checks": [
    "Verify exactly two children, two kick scooters and one toy box: the children are included in the two scooter actors, never duplicated as separate actors.",
    "Evaluate 941 samples at 20 Hz over -7..40 s; maintain the 2.9 m lateral separation of scooter roots and check articulated scooter, child and hand envelopes during both manual pivots.",
    "Show Child A braking, looking back, returning south, crouching and lifting the object while Child B continues north.",
    "Verify ground contact through curb transitions without inventing a ramp; the child may articulate and hand-lift the lightweight scooter while the composite support root remains grounded.",
    "Verify continuous pickup at 5.3..6 s and attachment without a position jump; retain the same toy ID in the hand through the final frame.",
    "Keep ego stopped at x=12 until at least 16 s, after both complete footprints and the carried box are on the north sidewalk.",
    "Require full-timeline human review before Image 2.5 edits original Image 1; unresolved source-vehicle or curb conflicts block image generation."
  ],
  "assumptions": [
    "All children, scooters, the toy and their coordinates are counterfactual additions. Original Image 1 supplies the residential streetscape; the wheelchair map supplies the road and sidewalk polygons.",
    "The unspecified retrieved object is authored as one small toy box already lying in the road at -7 s. No unseen fall or prior attachment is asserted.",
    "The crossing is transverse and unmarked at x=33.4 and x=36.3. No new crosswalk or curb ramp is assumed; the composite riders hand-walk or hand-lift their scooters at existing curb transitions.",
    "Playback is finite and non-looping at 20 Hz from -7 through 40 s. Use bounded C1 motion, rolling speeds up to approximately 2.1 m/s, ordinary walking during the return, and zero translational velocity during planted manual turns.",
    "Ground uses the supplied plane. Human and wheel support roots have z=0; toy key heights at attachment compensate the plane gradient so the local hand offset meets the world path.",
    "Ego is the simulator vehicle, approximately 4.6 by 1.85 m, stopped with its center at x=12, y=0 by -3 s. Release at 16 s is conditional on an actually clear buffered corridor.",
    "Exact curb profiles and photographed parked-vehicle depths are uncertain. The 4.4 s review seek point does not replace approval of the complete rehearsal; no image generation has been performed."
  ]
}