Domain: Engineering — Structural Engineering
Target concept: Spherical shell experiences uniform loading with no significant deformation.

Video generation prompt: Two thin-shell structural models are placed side by side on the table, with the left one being a spherical shell and the right one a cylindrical shell. Both are subjected to the same uniformly distributed pressure, applied simultaneously and increased at the same rate for the same duration.

Evaluation guide:
(i) Target concept: Structural stability of doubly-curved vs. singly-curved thin shells under uniform external pressure.
Minimum mechanism: Shell geometry must be the sole variable; material, thickness, boundary support, and loading must be identical; buckling requires compressive hoop stress in the cylinder, which is absent in the sphere due to its coupled meridional and hoop stresses.
(ii)Storyline: Frame 0–2: Static shot showing the two thin-shell models side by side on the table, sphere on the left, cylinder on the right, otherwise matched in size and finish. Frame 3–6: A transparent or neutral-colored pressure plate descends uniformly and contacts both models' entire upper surfaces at the same time. Frame 7–10: The cylindrical shell develops visible lateral buckling (a dimple, a waist, or an oval cross-section) while the spherical shell keeps its smooth, symmetric curvature with no visible deviation from its starting shape. Viewpoint stays fixed, frontal, level with the equator of both shells; no occlusion; lighting stable and diffuse.

Manual:
Experimental Procedure
1. Place a spherical shell model and a cylindrical shell model side-by-side on a flat table.
2. Apply identical uniform pressure simultaneously to the top surface of both models.
3. Observe deformation onset.
Observation of Experimental Phenomena
The cylindrical shell buckles or loses circular symmetry while the spherical shell remains perfectly undeformed under identical loading.
Summary of Experimental Principles
Spherical shells experience uniform loading with no significant deformation due to optimal stress distribution across doubly-curved geometry, whereas cylindrical shells lack circumferential curvature continuity and buckle under uniform pressure.

Prompt Grounding rubric:
level_1: Fewer than two shell models are visible; or the two models are not placed on a table at all; or no pressure-application device or action is shown.
level_2: Both the spherical and cylindrical shell models are present, but they are not placed side by side on the same table surface (e.g., one is stacked on the other, or they are far apart at different depths); or a pressure device is shown but it never visibly contacts one of the two models' top surfaces.
level_3: A spherical shell model on the left and a cylindrical shell model on the right sit side by side on the same flat table surface; a pressure-application device (e.g., a descending plate) contacts the full upper surface of both models at the same time; the device only begins descending after both models are shown resting in place.
level_4: Everything described at the 3-point level holds, and in addition: both models read as thin-walled shells rather than solid blocks; the pressure device's contact with each model's top surface is continuous and covers the whole surface with no visible gap on either side; no extraneous prop (a hand, a tool, a spare device) lingers in frame once the pressure device starts descending.
level_5: Everything described at the 4-point level holds, and in addition: the pressure device descends at the same visible rate over both models with no pause favoring one side; both models share the same surface finish, color, and reflectivity, so geometry is the only visible difference between them; the table, the models, and the pressure device stay the same size and position relative to the camera throughout the setup phase.

Scientific and Causal Correctness rubric:
level_1: The spherical shell visibly deforms while the cylindrical shell stays rigid (the reverse of the expected pattern), or both shells end the sequence in the exact same visual state, either both staying smooth and undeformed or both showing visible buckling, so no differential response between the two geometries is shown at all.
level_2: The cylindrical shell shows some visible change, but it looks the same in kind and severity as whatever change (if any) affects the spherical shell (for instance, both shells show similar mild surface waviness), so the two geometries can't be told apart by their response, even though the two end states aren't perfectly identical.
level_3: Once the pressure device has fully seated on both models, the cylindrical shell develops a visible loss of its circular cross-section (an oval profile, a dimple, or local waviness), while the spherical shell keeps its smooth, closed, round curvature with no visible change from its starting shape.
level_4: Everything described at the 3-point level holds, and in addition: the cylindrical shell's shape change stays confined to its curved side wall rather than its flat rim or base; the spherical shell shows no visible whitening, creasing, or shadow change hinting at internal strain; the cylindrical shell's shape change only begins once the pressure device has fully contacted it, not before.
level_5: Everything described at the 4-point level holds, and in addition: the cylindrical shell's buckling visibly starts near its mid-height and spreads outward from there rather than starting at the rim; the spherical shell's outline matches its pre-pressure outline for the entire sequence; neither shell shows an implausible recovery, such as the cylindrical shell popping back to a perfect circle while pressure is still visibly applied.

Spatiotemporal Consistency rubric:
level_1: One or both shell models jump to a new position on the table between frames with no motion shown getting them there; the table surface itself flickers, disappears, or reappears; a shell model dissolves, morphs into the other shape, or shatters with no mechanical event shown causing it; the lighting flips abruptly between bright and dim with no visible cause partway through the sequence.
level_2: The pressure device's descent looks inconsistent between the two models: for instance, it moves smoothly toward the cylinder but skips or jumps frames approaching the sphere; a crack or gap appears in a shell wall with no load event shown that would explain it; part of a shell model is hidden behind an object that wasn't present a moment earlier.
level_3: Both shell models stay in the same table position and orientation from the first frame to the last; the pressure device moves toward both models without skipping or reversing; the lighting stays constant in direction and brightness, and the shadows it casts don't shift; neither model's silhouette is blocked by an unexplained object at any point.
level_4: Everything described at the 3-point level holds, and in addition: the table's surface texture stays consistent under both the models and the pressure device with no sudden change in resolution or pattern; the edges of both shells stay sharp and single, with no doubled or flickering outlines, as the pressure device approaches and contacts them; the pressure device travels straight down without tilting or wobbling to one side.
level_5: Everything described at the 4-point level holds, and in addition: the relative sizes and positions of the two shells and the pressure device stay proportionally consistent with one fixed camera viewpoint, with no shell appearing to grow, shrink, or shift in depth relative to the other as the device descends; the device's descent speed looks constant rather than speeding up or stalling between frames; neither shell's surface shows warping or smearing beyond what the buckling itself would produce.