Domain: Humanities and Social Sciences — Arts
Target concept: Oil Painting - Color

Video generation prompt: Display a palette on which the painter has placed equal amounts of red and blue pigment, using a palette knife to gently mix them.

Evaluation guide:
(i) Target concept: Subtractive pigment mixing in oil painting, where physical juxtaposition and mechanical blending of red and blue yields purple through spectral absorption.
Minimum mechanism: Red and blue pigments must be spectrally complementary (not RGB light); their physical co-location and shear-induced dispersion must occur on a static substrate; resulting purple must emerge *only* at the interface and scale with contact extent.
(ii)Storyline: Frame opens on static palette with two separate, identically sized mounds of red and blue pigment placed adjacent (not overlapping). Palette knife enters frame, makes contact with both mounds simultaneously at their shared boundary. Knife moves steadily along the boundary, inducing progressive intermingling. A narrow, continuous purple band emerges *in real time* along the path of knife contact, neither before contact nor beyond its reach. Motion ceases; purple band stabilizes, bounded by unchanged red and blue zones. Viewpoint remains fixed, frontal, and level; no object leaves frame or changes scale; lighting remains uniform and directional.

Manual:
Experimental Procedure
1. Place a wooden artist"s palette flat in frame.
2. Deposit one distinct mound of red oil paint and one distinct mound of blue oil paint side-by-side on the palette surface.
3. Pick up a metal palette knife and gently drag its edge across the boundary between the two mounds.
Observation of Experimental Phenomena
A contiguous transitional zone of purple appears exclusively where the knife contacts both red and blue pigments; red and blue remain visually distinct outside this zone; no other colors emerge.
Summary of Experimental Principles
Oil painting color mixing follows subtractive color theory: overlapping red and blue pigments absorb complementary wavelengths, reflecting purple; physical blending via palette knife enables controlled chromatic transition without full homogenization.

Prompt Grounding rubric:
level_1: No palette is visible; no red pigment mound is present; no blue pigment mound is present; no palette knife appears; and no mixing action of any kind is shown.
level_2: The palette is present but only one pigment color (red or blue, not both) is placed on it; or the palette knife appears in frame but never touches either pigment mound; or both mounds are present but are obviously mismatched in size rather than roughly equal amounts.
level_3: The palette shows both a red mound and a blue mound placed side-by-side (not overlapping) in roughly equal amounts, and the palette knife is visibly touching both mounds at their shared edge, but the knife has not yet started any dragging or mixing motion.
level_4: Everything from score 3 holds, and the knife performs a steady dragging motion along the boundary between the red and blue mounds, with the two colors visibly starting to intermingle at the contact line as the knife moves; the knife and both mounds stay continuously visible with no jump in their positions from one frame to the next, but the motion looks slightly less smooth than a real hand stroke, e.g. one brief pause-and-restart in the knife's travel.
level_5: Everything from score 4 holds, the knife completes a continuous stroke along the entire length of the boundary it set out to cover, the knife itself stays fully visible and consistently angled against the palette surface throughout the stroke, and neither the knife nor either pigment mound flickers, is unexpectedly occluded, or breaks apart structurally at any point in the video (the resulting hue of the blended region is judged separately and is not part of this criterion).

Scientific and Causal Correctness rubric:
level_1: No color change occurs anywhere on the palette; the red and blue mounds show no sign of interacting with each other; no purple hue appears at their boundary; and the pigment itself never changes from its original undisturbed mound shape.
level_2: The red and blue mounds sit next to each other but nothing about the knife's motion explains any purple that appears, e.g., purple shows up somewhere the knife never touched, or purple appears in the frame before the knife makes contact with the boundary between the two mounds.
level_3: The red and blue mounds are placed side-by-side, the knife contacts the boundary between them, and a continuous band of purple appears only along the exact path the knife traces across that boundary, while the rest of the palette away from the knife's path stays purely red or purely blue.
level_4: Everything from score 3 holds, and additionally the purple band only begins to appear once the knife starts moving across the boundary and continues to widen or extend only as long as the knife keeps working new sections of the boundary; once the knife stops moving, the purple band stops growing but the purple that has already formed remains visible rather than fading or vanishing; the red and blue elsewhere on the palette keep their original hue, and no third color (green, orange, brown) appears anywhere in the blend.
level_5: Everything from score 4 holds, and the purple band shows a graded transition (more red-leaning near the red mound and more blue-leaning near the blue mound) rather than a single flat, uniform purple, with no obvious abrupt color stripes or sudden hue jumps across the band; the pigment surface keeps looking like thick oil paint (no runniness, dripping, or dried/cracked texture) throughout the blending.

Spatiotemporal Consistency rubric:
level_1: The palette itself disappears and reappears between shots; the red or blue pigment mound vanishes and reappears in a different spot without the knife ever touching it; the palette knife disappears mid-stroke and reappears elsewhere; the camera's viewpoint suddenly jumps or rotates instead of holding a fixed angle; or the room lighting changes abruptly, such as a sudden flash or the palette's shadow vanishing entirely from one frame to the next.
level_2: The palette stays visible but its position or tilt suddenly changes between frames with no camera movement to explain it; part of a pigment mound smears away or vanishes without the knife ever passing over it; the knife appears to pass through a pigment mound without leaving any dent, displacement, or smear behind it; or the knife's own shadow on the palette surface jumps to the opposite side of the knife between consecutive frames instead of staying on one consistent side.
level_3: The palette holds a fixed position and orientation in frame; the red and blue mounds stay put relative to the palette's edges except where the knife actively disturbs them; the palette knife moves continuously and stays fully visible throughout its stroke; and the knife's shadow on the palette stays on the same side of the knife, at a roughly constant length, for the whole video.
level_4: Everything from score 3 holds, and additionally the knife's stroke looks physically natural (no sudden jerks, floating above the surface, or unnatural speed changes); the edges of the two pigment mounds visibly deform (smear, ridge, or furrow) exactly where the knife presses into them, and the knife never appears to pass behind a pigment mound without the mound correctly occluding part of it.
level_5: Everything from score 4 holds, and additionally the sense of depth between the raised pigment mounds and the flat palette surface stays consistent as the knife moves (nearer parts of the mounds appear to shift slightly more than farther parts, matching a believable camera perspective); no frame shows the knife or pigment duplicated, strobing, or stuttering in place; and the pigment's paint-like texture (grain, gloss, ridges left by the knife) looks stable and continuous from one frame to the next, with no warping or stretching of the palette or knife.