Domain: Humanities and Social Sciences — Arts
Target concept: Comparing matte spheres and glossy spheres under the same directional lighting conditions

Video generation prompt: Two identical spheres, one matte and the other glossy, are placed side by side under a light source of fixed direction and rotate together.

Evaluation guide:
(i) Target concept: Surface reflectance dichotomy (diffuse vs. specular reflection) under directional illumination.
Minimum mechanism: Light must arrive from a single dominant direction; spheres must be geometrically identical and co-rotating; observer viewpoint must remain fixed to preserve comparative visibility of highlight behavior.
(ii)Storyline: Frame 0–1: Two spheres enter static view, side-by-side, under directional light; identical shape and alignment confirmed. Frame 2–4: Rotation begins synchronously; highlight appears on glossy sphere at light-facing region; matte sphere shows no localized bright spot. Frame 5–8: Rotation continues; highlight migrates smoothly across glossy sphere surface; matte sphere maintains uniform luminance. Frame 9–10: Final orientation confirms persistent, unambiguous contrast in reflection behavior; no occlusion, no lighting shift, no material ambiguity.

Manual:
Experimental Procedure
1. Place two identical spheres side-by-side on a neutral surface.
2. Illuminate them from a single fixed-direction light source.
3. Rotate both spheres together at the same speed and axis.
Observation of Experimental Phenomena
The matte sphere shows uniform, soft illumination with no concentrated highlight; the glossy sphere shows a bright, compact, moving highlight whose position shifts with rotation — both responses remain stable and distinguishable throughout.
Summary of Experimental Principles
Matte surfaces scatter incident light diffusely in all directions, producing low-contrast, even brightness; glossy surfaces reflect light specularly, producing a high-contrast, directionally sensitive highlight whose location depends on viewer, light, and surface normal.

Prompt Grounding rubric:
level_1: No two spheres present; or only one sphere visible; or spheres not identical in size/shape; or no directional light source visible; or spheres not rotating; or rotation not synchronous.
level_2: Two spheres present and rotating, but at least one of the following is missing: side-by-side spatial arrangement; fixed directional light source visibly illuminating scene; identical spherical shape confirmed; rotation occurring within same continuous shot.
level_3: Two identical spheres present, placed side-by-side in same scene under a clearly visible fixed-directional light source, and rotating synchronously; all core objects, spatial relationship, and action sequence from posted_prompt are present.
level_4: All conditions for score 3 satisfied, plus: both spheres maintain consistent relative position (no drifting apart or converging); light source remains stationary and unchanging in direction throughout; rotation axis and angular velocity appear visually matched between spheres.
level_5: All conditions for score 4 satisfied, plus: no frame-level discontinuity in placement, lighting, or motion; spheres remain fully visible and undistorted across entire duration; no visual artifact obscures side-by-side comparison or light interaction.

Scientific and Causal Correctness rubric:
level_1: No discernible surface finish difference between spheres; or both appear uniformly matte or uniformly glossy; or highlight behavior contradicts material properties (e.g., matte sphere shows sharp specular highlight, glossy sphere shows diffuse-only reflection).
level_2: A surface difference is visible but inconsistent with knowledge point: e.g., only one sphere shows any reflection; or reflection appears on wrong side relative to light; or brightness/distribution of reflections does not distinguish matte vs. glossy (e.g., both show equally sharp or equally soft highlights).
level_3: Two distinct surface responses to light are visibly present: one sphere shows broad, soft, low-contrast illumination with no concentrated highlight; the other shows a bright, compact, high-contrast highlight with clear falloff, matching matte vs. glossy optical behavior under directional lighting.
level_4: All conditions for score 3 satisfied, plus: highlight location on glossy sphere remains consistently aligned with light direction and sphere curvature; matte sphere shows no localized highlight at any frame; contrast difference between spheres is maintained continuously during rotation.
level_5: All conditions for score 4 satisfied, plus: no frame shows inversion or ambiguity in material identity (e.g., glossy sphere momentarily appearing matte due to occlusion or motion blur); highlight on glossy sphere moves smoothly and predictably with rotation; matte sphere maintains uniform luminance distribution without unintended specular leakage or shading anomalies.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal violation: spheres teleport between frames; light source flickers or jumps position; rotation reverses or stutters violently; spheres intersect or merge; background shifts abruptly.
level_2: Multiple moderate violations: e.g., intermittent sphere occlusion without recovery; light shadow direction changes inconsistently; rotation jerks or pauses more than once; partial structural deformation (e.g., sphere flattens or elongates).
level_3: At most one minor spatiotemporal flaw: e.g., brief momentary occlusion of one sphere edge; single-frame lighting inconsistency; or one subtle motion stutter, but no break in object integrity, lighting continuity, or rotational coherence.
level_4: No spatiotemporal flaws affecting object identity or causal reading: spheres retain rigid shape; light direction and intensity stable; rotation smooth and uninterrupted; no object clipping, warping, or background instability.
level_5: Zero spatiotemporal flaws: spheres maintain perfect geometric fidelity; lighting cast and ambient response fully consistent frame-to-frame; rotation motion is fluid, steady, and physically plausible without any perceptible interpolation artifact, warp, or temporal aliasing.