Domain: Engineering — Materials Science & Engineering
Target concept: A tempered glass and a regular glass were each impacted once by the same steel ball dropped from the same height, and the fracture patterns of the two were compared.

Video generation prompt: A tempered glass and a regular glass were each impacted once by the same steel ball dropped from the same height, and the fracture patterns of the two glasses were compared.

Evaluation guide:
(i) Target concept: Mechanical failure mode divergence due to residual stress state in thermally treated silicate glass.
Minimum mechanism: Tempered glass must be in a biaxial compressive surface / tensile core stress equilibrium; impact must breach the compressive layer to trigger explosive, isotropic fragmentation; regular glass must be in unstressed or annealed state to permit preferential crack propagation along flaws.
(ii)Storyline: [Frame 0–2] Static wide shot: two vertically mounted glass panels (left = tempered, right = regular) aligned in same plane, steel ball held at fixed height above first panel. [Frame 3–4] Ball release: identical drop initiation with visible gravity-driven acceleration. [Frame 5] First impact: contact with first panel, immediate radial deformation, then fracture pattern emergence within ≤100 ms visual latency. [Frame 6–7] Brief pause (no motion, no repositioning). [Frame 8] Second release and impact on second panel, identical mechanics. [Frame 9] Both fracture patterns fully visible and stable until end. Perspective: fixed frontal orthographic-like viewpoint, no zoom/pan, full panels always in frame.

Manual:
Experimental Procedure
1. Place tempered glass and regular glass panels side-by-side in fixed frame.
2. Drop identical steel ball from identical height onto first panel; record impact and fracture.
3. Drop identical steel ball from identical height onto second panel; record impact and fracture.
Observation of Experimental Phenomena
- Regular glass: long, sharp, radially propagating cracks forming large interlocking shards.
- Tempered glass: dense network of small, uniform, polygonal fragments covering entire impacted area.
Summary of Experimental Principles
Tempered glass undergoes thermal strengthening, inducing compressive surface stress; upon impact, stored energy causes instantaneous, full-thickness shattering into harmless granular pieces. Regular glass lacks this stress layer and fractures catastrophically along tensile flaws, producing dangerous sharp shards.

Prompt Grounding rubric:
level_1: Neither glass panel appears on screen, no steel ball is shown, no impact takes place, and no fracture of any kind becomes visible at any point in the clip.
level_2: A steel ball and at least one glass panel appear, but the tempered panel and the regular panel are not both present in the scene, or the ball strikes a surface without it being clear which panel type was hit, or no fracture ever becomes visible on either panel.
level_3: The tempered panel and the regular panel are both present in the same scene and clearly distinguishable from each other (through framing, position, or context), the ball strikes one panel and then the other (whether back-to-back or with a pause between), and at least one of the two impacts is followed by a visible fracture pattern.
level_4: Everything in the score 3 description holds, and in addition both panels sit side by side within a single fixed shot, the ball strikes each panel exactly once with a clear pause separating the two impacts, a fracture pattern follows each of the two impacts, and nothing else in the shot blocks either panel before, during, or after its impact.
level_5: Everything in the score 4 description holds, and in addition both panels remain visible side by side for the entire clip, the ball is dropped the same way onto each panel (same release height, same orientation, same path relative to its panel), each panel's fracture stays visible on screen from the moment it appears until the clip ends, nothing enters or exits the frame between the two impacts, and the whole sequence plays as one continuous shot with no cut between the two drops.

Scientific and Causal Correctness rubric:
level_1: Neither panel shows a fracture pattern; or both panels fracture the same way (e.g., both show only long radiating cracks, or both crumble into small pieces); or the tempered panel shows large angular shards like ordinary glass; or the regular panel shows small granular fragments like tempered glass.
level_2: Only one of the two panels shows a fracture pattern; or the pattern shown doesn't match its glass type (for instance the regular panel breaks into small uniform pieces, or the tempered panel shows a few long branching cracks radiating from the impact point); or a fracture appears without any impact having occurred.
level_3: Both panels show a fracture pattern; the regular panel shows long, sharp cracks radiating outward from the impact point with a small number of large shard boundaries; the tempered panel shows a dense field of small, roughly equal-sized polygonal fragments spread across most of the impacted area; neither panel shows the other's characteristic pattern.
level_4: Everything in the score 3 description holds, and in addition the regular panel's shards stay largely in their original positions or separate cleanly along the radiating cracks without further crumbling, while the tempered panel's small fragments stay held together in place (still roughly filling the panel's outline) rather than large chunks breaking free and falling away.
level_5: Everything in the score 4 description holds, and in addition the regular panel shows only long radiating cracks with clean shard edges and no fine crumbling anywhere on the panel, while the tempered panel's small polygonal fragments cover the entire impacted region edge to edge, with no leftover unbroken patch, no long radiating crack running through it, and no isolated area of partial breakage.

Spatiotemporal Consistency rubric:
level_1: The tempered panel or the regular panel is simply gone from one frame and back in a new spot the next, with no camera pan to account for the change; the steel ball vanishes mid-fall and reappears lower down; a fracture pattern appears on a panel before the ball has touched it, or a visible fracture disappears and comes back; the lighting or shadow direction on the panels flips abruptly with no physical cause; or the camera's viewpoint jumps to a new angle with no motion connecting the two shots.
level_2: One of the two panels shifts to a different position between its pre-impact and post-impact appearance; the ball's fall visibly bends, pauses, or changes speed for no physical reason; the fracture pattern on a panel appears in separate disconnected bursts rather than spreading continuously; or the background behind the panels flickers or changes shape between frames.
level_3: The camera shows slight jitter during one of the two impacts; one panel is briefly and only partially hidden during its impact without hiding the start of its fracture; or one panel's shadow looks slightly different from the other's, without affecting whether its fracture is visible. Otherwise nothing else in the shot is out of place.
level_4: Both the tempered panel and the regular panel stay right where they were set up, fully visible, through both impacts; the ball falls in one continuous, unbroken path toward each panel in turn; each fracture pattern spreads frame by frame with no skips or resets partway through; and the shadows cast by the panels and the ball point in the same direction and keep the same strength across both impact events, changing only as the ball's own position changes.
level_5: Everything in the score 4 description holds, and in addition the ball's apparent size and position relative to each panel change smoothly and consistently with its falling distance (no sudden size jump as it nears either panel); no part of the ball or either panel warps, stretches, or briefly smears out of shape during the high-speed impact moment; and neither fracture pattern's spread shows any ghosting or doubled trailing image as it propagates across the panel.