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Skull

Benchmark instance 074
Input static SVG
Input static SVG for Skull
Source Lottie animation
Motion edit prompt

Animate the skull as mostly rigid line art with two repeated jaw-chatter cycles. From the closed pose, the entire skull first rocks slightly counterclockwise around a pivot near the rear jaw/neck connection, then rotates back to its upright angle in the provided SVG. Without a pause as the skull rotates back upright, rotate the lower jaw as one separate piece around the back hinge under the cheek: it swings downward first into an open-mouth position while the upper skull stays in place, carrying the lower teeth marks with it. The jaw then snaps back upward to meet the upper teeth, makes a tiny reopening rebound, and settles fully closed. After a short closed pause, repeat the same sequence once more: small counterclockwise head rock, lower jaw immediately drops open, snaps shut, lightly rebounds, and ends closed.

Example model outputs

Human-approved

Kimi K3

Reasoning effort: maximum

Verification report: 6 passed · 0 failed
Result Check
PASS ver_handoff_and_closed_pause

Carried closed rock, continuous handoff, still upper skull, inter-cycle closed pause

Measured values 
{
  "carry_error": 0.0012314661330234855,
  "handoff_windows": [
    [
      [
        20,
        21
      ],
      [
        17.93303506785037,
        19
      ]
    ],
    [
      [
        71,
        72.35081640354248
      ],
      [
        67.76106881277109,
        69
      ]
    ]
  ],
  "upper_hold_error": 0.10062842326256412
}
PASS ver_head_rocks_twice

Two counterclockwise rocks, returning to the upright drawing

Measured values 
{
  "anchor_error": [
    0.00100000000009004,
    0.00100000000009004
  ],
  "angle_range": [
    -6.000101084230835,
    0.0
  ],
  "rocks": [
    12,
    62
  ]
}
PASS ver_jaw_chatter_twice

Open, upward return, smaller reopening; repeated twice

Measured values 
{
  "peaks": [
    20.0,
    4.941,
    19.9988,
    4.9996
  ],
  "valleys": [
    0.0,
    2.6474
  ]
}
PASS ver_rear_hinges

Fixed turns at the rear attachments, without detachment/translation

Measured values 
{
  "fits": [
    [
      "head",
      [
        830.0033390301986,
        690.0017602829042
      ],
      0.0011727795415446608,
      0.03671889566971678
    ],
    [
      "head",
      [
        830.0040575538786,
        690.002554084196
      ],
      0.0011684411403496107,
      0.036821320726747785
    ],
    [
      "jaw",
      [
        986.0006735331755,
        675.0000444457354
      ],
      0.0007705530593344926,
      0.017415604744884877
    ],
    [
      "jaw",
      [
        986.005413042729,
        674.9976837027549
      ],
      0.0009510781291051353,
      0.07015835910064114
    ],
    [
      "jaw",
      [
        985.9999127536265,
        675.0004067635665
      ],
      0.08005949576377844,
      0.017416698797788087
    ]
  ]
}
PASS ver_rigid_line_art

Visible rigid outlines, carried tooth marks, and unchanged paint

Measured values 
{
  "mask_attachment": {
    "worst_root_clearance": -0.16379050126754233
  },
  "max_outline_error": 0.0017217508633729348
}
PASS ver_teeth_meet_closed

Closed start/end and tooth contact at the returns

Measured values 
{
  "endpoint_gaps": [
    0.000898994503251843,
    0.0008989953395335788
  ],
  "impacts": [
    [
      18,
      0.3240108316275575,
      1.1811150019863494
    ],
    [
      33,
      0.000898994503251843,
      26.86067043086927
    ],
    [
      60,
      0.00037689532979588806,
      0.0012966187008121549
    ],
    [
      68,
      1.078441729474275,
      0.4653938774507542
    ],
    [
      84,
      8.866242639082767,
      12.054969768034377
    ],
    [
      90,
      0.0008989953395335788,
      0.0
    ]
  ]
}

Human-rejected

Gemma 4 31B IT

Reasoning effort: high

Verification report: 3 passed · 3 failed
Result Check
FAIL ver_handoff_and_closed_pause

Carried closed rock, continuous handoff, still upper skull, inter-cycle closed pause

Measured values 
{
  "carry_error": 30.299472932702436,
  "handoff_windows": [
    [
      [
        17,
        19.001870602813774
      ],
      [
        9,
        9
      ]
    ],
    [
      [
        67,
        68.49480737826761
      ],
      [
        58,
        58
      ]
    ]
  ],
  "upper_hold_error": 0
}
PASS ver_head_rocks_twice

Two counterclockwise rocks, returning to the upright drawing

Measured values 
{
  "anchor_error": [
    0.00100000000009004,
    0.00100000000009004
  ],
  "angle_range": [
    -5.000266894130931,
    2.842170943040401e-14
  ],
  "rocks": [
    9,
    58
  ]
}
FAIL ver_jaw_chatter_twice

Open, upward return, smaller reopening; repeated twice

Measured values 
{
  "positive_peaks": [
    9,
    27,
    36,
    58,
    76,
    85
  ]
}
FAIL ver_rear_hinges

Fixed turns at the rear attachments, without detachment/translation

Measured values 
{
  "fits": [
    [
      "head",
      [
        1200.0059512510759,
        649.989147845787
      ],
      0.0015340097273340726,
      0.04447401048985542
    ],
    [
      "head",
      [
        1199.9969585341046,
        650.0053590237566
      ],
      0.0015802952563999857,
      0.044612772287218584
    ],
    [
      "jaw",
      [
        1179.9993061811833,
        719.9992347636288
      ],
      0.0007899466579975108,
      0.028475476325982144
    ],
    [
      "jaw",
      [
        1180.0002864505836,
        720.001338621609
      ],
      0.0196558713263294,
      0.028562903482920038
    ],
    [
      "jaw",
      [
        1180.003031803544,
        720.0101671401424
      ],
      0.0009177586829918537,
      0.11512721887387332
    ]
  ]
}
PASS ver_rigid_line_art

Visible rigid outlines, carried tooth marks, and unchanged paint

Measured values 
{
  "mask_attachment": {
    "worst_root_clearance": 0
  },
  "max_outline_error": 0.0017400325766556205
}
PASS ver_teeth_meet_closed

Closed start/end and tooth contact at the returns

Measured values 
{
  "endpoint_gaps": [
    0.000898994503251843,
    0.000898994503251843
  ],
  "impacts": [
    [
      18,
      0.000898994503251843,
      2.381640868657636
    ],
    [
      31,
      0.27699800750611314,
      1.1171455734030138
    ],
    [
      41,
      0.000898994503251843,
      0.03439993348627509
    ],
    [
      67,
      0.034232335733461114,
      1.203378545105964
    ],
    [
      81,
      0.000898994503251843,
      1.1148956208452516
    ],
    [
      90,
      0.000898994503251843,
      0.0
    ]
  ]
}