Domain: Engineering — Geotechnical Engineering
Target concept: Coarse sand and sand with mixed particle sizes are poured into the same cylindrical container and subjected to tapping.

Video generation prompt: Two identical transparent cylinders, each filled with sand of equal height — one consisting of uniform coarse sand and the other of mixed-sized sand — are placed side by side on a rigid surface and subjected to repeated impacts.

Evaluation guide:
(i) Target concept: Differential compaction of granular materials under mechanical excitation, governed by particle size distribution.
Minimum mechanism: Sand must be dry, cohesionless, and free-flowing; tapping must induce particle rearrangement (not fracture or ejection); containers must be rigid and non-deformable; gravity must dominate over inertial effects during settling.
(ii)Storyline: Frame 0–2: Static side-by-side view. Two transparent cylinders, equal sand height, grain size difference immediately apparent. Frame 3–4: Tapping motion initiates. Identical impact gesture approaches both cylinders synchronously. Frame 5–7: Contact and transmission. Both cylinders experience simultaneous impulse; sand surfaces begin subtle downward displacement. Frame 8–10: Post-impact settling. Mixed sand height visibly reduced relative to uniform sand; no lateral motion, no fluid behavior, no rebound; final state holds until video end. Perspective: Fixed frontal orthographic or slight low-angle view ensuring full visibility of both cylinder profiles and sand surfaces throughout.

Manual:
Experimental Procedure
1. Place two identical transparent cylindrical containers side-by-side on a rigid horizontal surface.
2. Fill each with dry sand to equal height: left cylinder with uniform coarse sand; right cylinder with sand containing visibly mixed particle sizes.
3. Apply repeated identical vertical impacts (tapping) simultaneously to both containers.
Observation of Experimental Phenomena
After tapping, the mixed-size sand settles to a significantly lower final height than the uniform coarse sand; grain size heterogeneity is visually distinguishable before and during tapping.
Summary of Experimental Principles
Coarse uniform sand has higher void ratio and resists rearrangement; mixed-size sand achieves greater packing density under vibration due to smaller particles filling voids between larger ones — resulting in greater compaction under tapping.

Prompt Grounding rubric:
level_1: No transparent cylindrical containers are visible; no sand appears inside any container; the two containers never appear together in the same shot; no tapping or impact action is shown; the sand in the two containers looks identical, with no coarse-vs-mixed grain contrast at all.
level_2: A transparent cylinder with sand is visible, but only one container ever appears on screen instead of both together; or both containers appear but sit far apart or one behind the other rather than side by side on the same surface; sand is present but no tapping motion ever touches either container; or the grain-size difference between the two sands is not visible (both look uniformly coarse, or both look like a mixed blend).
level_3: Two transparent cylindrical containers stand next to each other on the same rigid surface; both hold sand filled to about the same height; the sand in one cylinder looks like large, evenly sized coarse grains, while the sand in the other clearly shows grains of noticeably different sizes mixed together; a tapping or striking action is shown hitting the containers, though the timing between the two impacts may be somewhat off or the striking motion may look a bit different on each side.
level_4: All conditions for score 3 are met; in addition, the two cylinders keep their positions next to each other under one fixed camera angle and lighting setup for the whole clip; the uniform-coarse-sand cylinder and the mixed-sand cylinder each stay on the same side throughout, with no swap; the tapping strikes both cylinders at essentially the same moment, or in a clearly matched back-and-forth rhythm (e.g., tap left, tap right, tap left, tap right at even intervals).
level_5: All conditions for score 4 are met; in addition, both cylinders sit perfectly still before the first tap, with level, undisturbed sand surfaces; nothing drifts into frame to block either cylinder at any point; each tap comes from the same relative height, angle, and side for both cylinders; whether the sand actually settles more in one cylinder than the other is not required for this score, only that the setup and tapping action match the prompt exactly.

Scientific and Causal Correctness rubric:
level_1: Neither sand column changes height at all after tapping; or both cylinders settle by the same amount despite their different grain compositions; or the uniform coarse sand ends up settling more than the mixed-size sand; or the grains shown contradict which cylinder is supposed to hold mixed sizes (e.g., the cylinder meant to show mixed sizes shows only same-sized grains).
level_2: One cylinder's sand surface drops after tapping while the other shows no change at all; or both cylinders' sand surfaces drop by a visually identical amount; or the grain-size assignment is swapped (the container meant to be uniform coarse sand shows mixed grain sizes and vice versa); or the sand surface drops before any tapping has occurred.
level_3: After tapping begins, the mixed-size sand's surface drops noticeably more than the uniform coarse sand's surface; the coarse sand's grains look large and roughly the same size as one another, while the mixed sand's grains clearly include a range of sizes from small to large; the sequence of cause and effect is clear, since the surface drop happens only once tapping starts.
level_4: All conditions for score 3 are met; in addition, the mixed sand's surface drop is steady and one-directional, never bouncing back up or oscillating; neither sand column shows grains sliding sideways, splashing, or behaving like a liquid; both sands stay solid and granular throughout, with no clumping into a slurry and no grains floating; the transparent walls of both cylinders stay clear enough to see the sand level the entire time.
level_5: All conditions for score 4 are met; in addition, the two sand surfaces start at the same height and only begin to diverge once the first tap lands, with no pre-existing gap that widens on its own beforehand; at every point after tapping starts, the mixed-sand surface sits at or below the uniform-sand surface, never higher; individual grains keep their size and shape throughout, with none merging, dissolving, or changing size as settling proceeds.

Spatiotemporal Consistency rubric:
level_1: A cylinder or its sand disappears and reappears, or jumps to a new position on the surface, between frames; the sand's color or the room's lighting flips abruptly from one frame to the next; a cylinder's wall visibly bends, stretches, or warps; the background behind the cylinders disappears or changes without explanation; the tapping tool or hand appears mid-strike with no approach shown, or vanishes mid-motion.
level_2: One cylinder is briefly blocked from view and reappears in a slightly different spot than before; the sand surface height changes suddenly from one frame to the next with no gradual transition in between; the tapping motion skips frames or stutters noticeably; the shadow cast by a cylinder or the tapping hand changes shape abruptly with no matching change in the light source or object position.
level_3: Both cylinders stay in the same left-right positions relative to each other throughout the clip; the sand surface only moves the way gentle, gradual settling would look, with no sideways sliding, sudden jumps, or grains flying upward; the tapping motion shows a clear approach, contact, and pull-back rather than snapping into contact; the light source in the scene stays in one place, so shadows cast by the cylinders never swing to a new direction partway through; neither cylinder's walls crack, bulge, or separate from its base.
level_4: All conditions for score 3 are met; in addition, the settling of sand grains during and after each tap looks like continuous small movement rather than freezing and then jumping to a new level; both cylinder bases stay planted on the rigid surface the whole time, without lifting, rocking, or bouncing; the two cylinders keep the same relative size to each other in every frame, with no unexplained zoom on one but not the other; the rim of each cylinder and the sand-surface line stay aligned from frame to frame rather than jumping around.
level_5: All conditions for score 4 are met; in addition, the sand surface in each cylinder settles as one smooth, connected motion from top to bottom rather than in disconnected chunks or visible steps; the point where the tap contacts each cylinder stays in the same place relative to that cylinder's centerline throughout the sequence; the settling of the sand is never shown happening before the tap that supposedly causes it; both cylinders' outlines and sand lines stay crisp and easy to read, with no flicker or smearing between frames.