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Newton cradle

Benchmark instance 052
Input static SVG
Input static SVG for Newton cradle
Source Lottie animation
Motion edit prompt

Animate each hanging eye assembly as a rigid pendulum pivoting from the top end of its string. Starting from the current outward-splayed pose, the left string-and-eye swings inward to the right first while the right string-and-eye swings inward to the left first, both traveling along shallow downward arcs toward the center until the two eye whites touch at the center of the SVG scene; then they reverse and swing back outward to the angles they have in the provided SVG. Use smooth ease-in/ease-out at the extremes with a slight lingering pause at the outward positions, and perform the mirrored inward-and-outward swing 4 times total as a seamless loop. Keep the strings straight and attached to the eyes, keep the eye whites the same size, and let the pupils follow with a tiny delayed overshoot so they subtly translate and rotate inside the eyes, shifting toward the outer edge of each eye first, moving furthest off-center just after each eye assembly reaches either the inward or outward extreme, and recentering as the eye assemblies pass midway between the extremes.

Example model outputs

Human-approved

Claude Opus 5

Reasoning effort: maximum

Verification report: 8 passed · 0 failed
Result Check
PASS ver_artwork_and_white_size

Artwork retains its visible shape, size and paint

Measured values 
{
  "maximum_contour_shape_error": 0.004584801958912976
}
PASS ver_eased_extremes_and_outward_linger

Both motions slow at their extremes, with outward lingering rather than constant-speed reversal

Measured values 
{
  "endpoint_and_peak_travel": [
    [
      "left",
      [
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ],
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ],
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ],
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ]
      ]
    ],
    [
      "right",
      [
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ],
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ],
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ],
        [
          0.0,
          11.8105,
          3.0681
        ],
        [
          1.381,
          7.9541,
          1.3812
        ]
      ]
    ]
  ]
}
PASS ver_eye_whites_touch_at_center

The whites meet at the central inward reversals

Measured values 
{
  "contacts": [
    [
      25,
      -0.0631,
      15.60317534636377,
      1920.0
    ],
    [
      68,
      -0.0631,
      15.60317534636377,
      1920.0
    ],
    [
      111,
      -0.0631,
      15.60317534636377,
      1920.0
    ],
    [
      154,
      -0.0631,
      15.60317534636377,
      1920.0
    ]
  ]
}
PASS ver_four_mirrored_downward_swings

Exactly four synchronized mirrored inward-and-outward arcs

Measured values 
{
  "inward_extremes": [
    [
      "left",
      [
        25,
        68,
        111,
        154
      ]
    ],
    [
      "right",
      [
        25,
        68,
        111,
        154
      ]
    ]
  ]
}
PASS ver_outward_pose_and_loop

The anchored outward pose returns without a visible loop-position jump

Measured values 
{
  "poses": [
    [
      "left",
      0.010049875621109488,
      0.00022360679773833608,
      0.0
    ],
    [
      "right",
      0.010060318086408147,
      0.0002236067978400207,
      0.0
    ]
  ]
}
PASS ver_pupil_delayed_overshoot_and_recentering

Pupils move outward first, overshoot after the turns, and pass back through the eye centers

Measured values 
{
  "extreme_frames_and_lags_in_samples": [
    [
      "left",
      0,
      25,
      2.0,
      1.9641765483752103
    ],
    [
      "left",
      43,
      68,
      2.0,
      1.9641765483752067
    ],
    [
      "left",
      86,
      111,
      2.0,
      1.9641765483752067
    ],
    [
      "left",
      129,
      154,
      2.0,
      1.9641765483752067
    ],
    [
      "right",
      0,
      25,
      2.0,
      1.9641715171419598
    ],
    [
      "right",
      43,
      68,
      2.0,
      1.9641715171419634
    ],
    [
      "right",
      86,
      111,
      2.0,
      1.9641715171419634
    ],
    [
      "right",
      129,
      154,
      2.0,
      1.9641715171419492
    ]
  ]
}
PASS ver_pupils_follow_inside_the_whites

Both pupils translate and rotate independently while staying within their whites

Measured values 
{
  "pupils": [
    [
      "left",
      168.7721,
      7.5308,
      -38.5547
    ],
    [
      "right",
      168.7723,
      7.5308,
      -38.5543
    ]
  ]
}
PASS ver_rigid_top_pendulums

Both straight attached pendulums preserve their geometry about fixed string tops

Measured values 
{
  "errors": [
    [
      "left",
      0.0001,
      0.0094,
      0.0117,
      0.0022,
      9.422152134278808e-05
    ],
    [
      "right",
      0.0002,
      0.0094,
      0.0114,
      0.0021,
      9.676334604807135e-05
    ]
  ]
}

Human-rejected

Gemma 4 31B IT

Reasoning effort: high

Verification report: 2 passed · 6 failed
Result Check
FAIL ver_artwork_and_white_size

Artwork retains its visible shape, size and paint

Measured values 
{
  "element": "svg/g[0]/g[7]/g[0]/path[0]"
}
PASS ver_eased_extremes_and_outward_linger

Both motions slow at their extremes, with outward lingering rather than constant-speed reversal

Measured values 
{
  "endpoint_and_peak_travel": [
    [
      "left",
      [
        [
          0.0,
          3.8205,
          0.6635
        ],
        [
          0.6635,
          3.8205,
          0.6635
        ],
        [
          0.0,
          5.6728,
          1.4738
        ],
        [
          0.6635,
          3.8205,
          0.6635
        ],
        [
          0.0,
          5.6728,
          1.4738
        ],
        [
          0.6635,
          3.8205,
          0.6635
        ],
        [
          0.0,
          5.6728,
          1.4738
        ],
        [
          1.4738,
          5.6728,
          0.0
        ]
      ]
    ],
    [
      "right",
      [
        [
          0.0,
          3.8204,
          0.6635
        ],
        [
          0.6635,
          3.8204,
          0.6635
        ],
        [
          0.0,
          5.6728,
          1.4738
        ],
        [
          0.6635,
          3.8204,
          0.6635
        ],
        [
          0.0,
          5.6728,
          1.4738
        ],
        [
          0.6635,
          3.8204,
          0.6635
        ],
        [
          0.0,
          5.6728,
          1.4738
        ],
        [
          1.4738,
          5.6728,
          0.0
        ]
      ]
    ]
  ]
}
FAIL ver_eye_whites_touch_at_center

The whites meet at the central inward reversals

Measured values 
{
  "contacts": [
    [
      39,
      699.8889,
      8.07345363455525,
      1920.0
    ]
  ]
}
FAIL ver_four_mirrored_downward_swings

Exactly four synchronized mirrored inward-and-outward arcs

Measured values 
{
  "angle_min": -22.0008,
  "inward": [
    39,
    82,
    125
  ],
  "outward": [
    21,
    64,
    107,
    150
  ],
  "side": "left"
}
FAIL ver_outward_pose_and_loop

The anchored outward pose returns without a visible loop-position jump

Measured values 
{
  "center_error": 665.1640597334165,
  "side": "left",
  "string_horizontal_component": 0.0,
  "top_error": 0.021683173199470628
}
FAIL ver_pupil_delayed_overshoot_and_recentering

Pupils move outward first, overshoot after the turns, and pass back through the eye centers

Measured values 
{
  "side": "left"
}
FAIL ver_pupils_follow_inside_the_whites

Both pupils translate and rotate independently while staying within their whites

Measured values 
{
  "pupils": [
    [
      "left",
      288.1719,
      16.2507,
      947.0035
    ]
  ]
}
PASS ver_rigid_top_pendulums

Both straight attached pendulums preserve their geometry about fixed string tops

Measured values 
{
  "errors": [
    [
      "left",
      0.0152,
      0.0091,
      0.0111,
      0.002,
      8.436635647862412e-05
    ],
    [
      "right",
      0.0152,
      0.0091,
      0.0111,
      0.002,
      9.484869130929376e-05
    ]
  ]
}