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 blue and yellow pigment, using oil painting mixing techniques, and gently mixed them with a palette knife.

Evaluation guide:
(i) Target concept: Subtractive color mixing of opaque oil pigments via mechanical blending on a rigid support.
Minimum mechanism: Two spectrally distinct, opaque, viscous pigment masses must be placed in direct physical adjacency on a non-absorbent or semi-absorbent rigid surface, and a rigid tool must apply shear force across their interface to produce intimate particle-level intermingling, enabling uniform wavelength absorption and resulting in a new, stable, intermediate hue.
(ii)Storyline: [Frame 0–2] Palette enters static view; blue pigment mass appears intact and stationary; yellow pigment mass appears intact and stationary; both are side-by-side with clear separation. [Frame 3–5] Palette knife enters frame, approaches interface, and makes first contact with both pigments simultaneously. [Frame 6–8] Knife moves continuously across interface, displacing and folding pigments; green hue emerges *only* along the path of contact and expands contiguously. [Frame 9–10] Motion ceases; final state shows stable green mass bridging original positions, with no residual unmixed pigment within it. Perspective remains fixed frontal-close; all objects fully visible and occlusion-consistent throughout.

Manual:
Experimental Procedure
1. Place a clean artist"s palette flat in frame.
2. Deposit one distinct, compact mass of blue oil pigment and one distinct, compact mass of yellow oil pigment side-by-side on the palette.
3. Use a metal palette knife to gently draw it across the boundary between the two pigments, blending them together.
Observation of Experimental Phenomena
Two adjacent, similarly sized masses of blue and yellow pigment transform at their interface into a contiguous, intermediate green mass; no unmixed blue or yellow remains within that green region.
Summary of Experimental Principles
In oil painting, blue and yellow pigments are subtractive primaries; when physically mixed, they reflect wavelengths corresponding to green, producing a chromatically intermediate green hue—demonstrating pigment-based color mixing rather than optical mixing.

Prompt Grounding rubric:
level_1: The palette is never shown, or neither the blue nor the yellow pigment mass appears, or the palette knife never appears, or no mixing motion is depicted at all.
level_2: The palette is clearly a painter's palette, but only one of the two pigment colors (blue or yellow) is present, not both; the palette knife is absent or not identifiable; no mixing motion occurs.
level_3: The palette holds both a blue and a yellow pigment mass, each a distinct, similarly sized deposit placed side by side; the palette knife is present and is being held or used by a hand; no motion brings the knife across the boundary between the two masses, or the knife touches only one of the two masses.
level_4: Both pigment masses are present side by side in similar size; the palette knife makes contact with both masses and is dragged across the boundary between them, visibly displacing pigment from both sides of the interface; whether the resulting mixed color reads as scientifically correct green is not assessed here (that is graded separately), but the knife's mixing pass itself must be clearly completed rather than merely grazing one edge.
level_5: Both pigment masses are present side by side in similar size; the palette knife makes a sustained, thorough pass across the entire length of the boundary between them, visibly folding and displacing pigment from both masses along the full contact zone, and the knife is lifted away at the end leaving the mixed region undisturbed in the final shot; the correctness of the resulting hue is graded under the science axis, not here.

Scientific and Causal Correctness rubric:
level_1: No color change occurs at the interface; the blue and yellow pigments remain fully separated with no shared hue anywhere even after the knife has passed over them; no green appears; the pigments look unchanged in hue apart from being pushed around.
level_2: The blue and yellow masses are adjacent and the knife passes between them, but no green hue appears anywhere in the frame; instead the pigments merely smear without blending, or they mix into an incorrect hue such as brown, gray, or purple.
level_3: A green hue appears somewhere in the frame after the knife pass, but it is not located at the boundary between the blue and yellow masses, for example green appears only on the knife blade, in the background, or as an isolated smear unconnected to where the knife actually crossed the interface.
level_4: A green hue appears at the boundary where the knife crossed between the blue and yellow masses, but the green region still shows visible streaks or isolated spots of unmixed blue or yellow inside it, or the green appears briefly and then fades or reverts before the video ends.
level_5: A single, continuous green region forms exactly along the path where the knife crossed the boundary between the blue and yellow masses, with no visible streaks or spots of unmixed blue or yellow remaining inside that green region, and the color reads as a plausible blend of the original blue and yellow, consistent with how oil pigments physically intermix under a palette knife.

Spatiotemporal Consistency rubric:
level_1: The palette's position flickers or jumps between shots; the pigment masses vanish and reappear; the palette knife jumps discontinuously between positions; the lighting shifts dramatically mid-video (for instance a shadow disappears and then reappears); or a pigment mass distorts unnaturally, such as melting into a liquid pool with no motion causing it.
level_2: The palette stays in the same place, but a pigment mass shifts position with no knife contact causing the move; the palette knife rotates or moves in a way inconsistent with the camera's fixed perspective; or the lighting changes so the same surface shows highlights in different places across frames with no apparent cause.
level_3: The palette stays fixed in frame; each pigment mass keeps its shape and position until the knife touches it; the knife's motion follows one continuous, coherent path across the interface; the direction and brightness of the light source look the same from the start of the video to the end; no object flickers or breaks apart unexpectedly.
level_4: All elements keep the same spatial relationships to one another; the hand-and-knife motion is continuous and looks mechanically plausible as a single connected movement; the lighting and shadow pattern on the palette and pigments look the same throughout the video; brief motion blur is visible only while the knife is actively moving, not at rest.
level_5: The palette shows no visible drift in position throughout the video; the two pigment masses keep the same shape, size, and placement until the knife reaches them; the knife makes contact only after both masses are fully placed and lifts away cleanly at the end of the mixing pass; the knife's motion is smooth and moves in one direction without reversing back and forth erratically; and the knife visibly stays in front of whatever pigment is beneath it at each moment, with no visible lighting, focus, or camera-angle change from the first frame to the last.