Domain: Humanities and Social Sciences — Arts
Target concept: Adding a cast shadow, a contact shadow, and a core shadow to a cube sketch

Video generation prompt: A hand, under the illumination of a single desk lamp, draws a cube on white paper using a graphite pencil, and adds a cast shadow and a contact shadow under a fixed side light source.

Evaluation guide:
(i) Target concept: Accurate visual representation of geometric shadow formation under unilateral illumination in observational drawing.
Minimum mechanism: A single directional light source must produce three distinct tonal/shadow phenomena on and around the cube: a cast shadow (thrown onto the adjacent paper surface), a contact shadow (the tight dark band directly beneath the cube where it meets the paper), and a core shadow (the gradual darkening on the cube's own occluded face), each governed by the cube's geometry, the lamp's direction, and the paper's surface.
(ii) Storyline: Frame opens with a static scene: a fixed side desk lamp, flat white paper, and a graphite pencil held in hand. The hand draws the cube's outline in continuous motion, then shades its three visible faces from light to mid-tone to dark according to their orientation to the lamp. Once the cube is shaded, the hand adds the cast shadow, emerging from the cube's down-light edge and extending across the paper in the direction opposite the lamp. Immediately after, the hand adds the contact shadow, a narrow dark band confined to the cube's base footprint, darkest where the cube touches the paper and easing outward. Throughout, the lamp stays fixed in position, every object keeps its spatial relationship to the others, and all tonal transitions follow the single lamp's direction. The viewpoint stays fixed, frontal-overhead, keeping the hand, paper, cube, lamp, and both shadows fully visible.

Manual:
Experimental Procedure
1. Position the desk lamp fixed at the side of the frame, illuminating downward onto the flat white paper.
2. The hand holds a graphite pencil and draws a wireframe cube outline on the paper, then shades its three faces in light, mid-tone, and dark values according to their orientation to the lamp.
3. Add the cast shadow, extending from the cube's down-light edge onto the paper surface.
4. Add the contact shadow, a tonally graded dark band directly beneath the cube's base.
Observation of Experimental Phenomena
- The cube outline shows three visible faces in correct perspective.
- The cast shadow appears as a continuous silhouette extending from the down-light edge, aligned opposite the lamp.
- The contact shadow appears as a darker band matching the cube's base footprint, graded from darkest at the contact line to lighter outward.
- The lit face of the cube is brightest, the side face is mid-tone, and the occluded face is darkest — this darkest face value is the core shadow.
Summary of Experimental Principles
- The cast shadow forms where the cube blocks the lamp's light from reaching the paper beyond it.
- The contact shadow forms where light is most completely blocked directly beneath the cube, producing a tight band of localized darkening distinct from the larger cast shadow.
- The core shadow forms on the cube's own occluded face, where its surface turns away from the lamp — a separate phenomenon from the contact shadow, even though both are darkest near where the cube meets its own or the paper's surface.
- The value hierarchy follows single-side illumination: light → mid-tone → dark corresponds to each face's orientation relative to the lamp.

Prompt Grounding rubric:
level_1: No hand is visible, no desk lamp appears, no white paper surface is shown, no graphite pencil appears, no cube shape has been drawn, and no side-positioned light source can be inferred from the scene.
level_2: At least one of the five required elements (hand, desk lamp, white paper, graphite pencil, cube outline) is present, but three or more of the five are missing, and there is no visual cue (e.g., an off-center lamp or asymmetric lighting) suggesting light is coming from the side.
level_3: All five elements are present: a hand, a desk lamp, white paper, a graphite pencil, and a recognizable cube outline drawn on the paper; the lamp's off-center position or the asymmetric lighting on the paper implies a side light source; however, the cast shadow and the contact shadow are either both missing, or one is missing, or either is placed somewhere clearly disconnected from the cube (e.g., floating away from its base, or on the wrong side of the cube).
level_4: All five elements are present and plausibly arranged: the hand is actively drawing or resting near the finished cube; the desk lamp sits fixed at the side; the paper lies flat with asymmetric lighting across it; the pencil is held naturally; the cube outline shows three visible faces in a believable perspective; both a cast shadow and a contact shadow are present and each sits in roughly the right place (the cast shadow reaching away from the cube on the side opposite the lamp, the contact shadow confined near the cube's base), but their position or size is only approximately right (e.g., the cast shadow's length or angle looks somewhat off, or the contact shadow noticeably overshoots or undershoots the cube's base outline).
level_5: All five elements are present, correctly arranged, and each remains recognizable throughout: the hand naturally holds the pencil in contact with the paper; the desk lamp stays fixed at its side position; the paper stays flat; the cube outline is complete with a plausible three-face perspective; the cast shadow extends from the cube in the direction away from the lamp with a length and angle that look proportionate to the cube's size; the contact shadow sits tightly confined to the cube's base footprint with plausible size; both shadows are clearly present, correctly placed relative to the cube and lamp, and proportioned believably, independent of how precisely their internal tone or edge quality is rendered.

Scientific and Causal Correctness rubric:
level_1: No causal relationship between the lamp and shadow formation is visible; the cube's face shading is random or unrelated to the lamp's position; both the cast shadow and the contact shadow are absent, swapped, or appear under diffuse/ambient lighting with no directional cue tying them to the lamp.
level_2: Only one of the cast shadow or contact shadow appears, and its placement contradicts the lamp's position (e.g., the shadow falls on the same side as the lamp rather than opposite it); the cube's face shading is inconsistent (e.g., a highlight appears on the occluded face, or all three faces are rendered with equal value); there is no visible correspondence between the lamp's location and where the shadows fall.
level_3: Both the cast shadow and the contact shadow appear and are directionally aligned with the lamp's position (both extend away from the lamp), but the cast shadow is not anchored to the cube's down-light edge, or the contact shadow does not sit within the cube's base footprint; the cube shows basic light/dark face variation but lacks the correct three-step tonal hierarchy (e.g., the occluded face reads lighter than the lit face).
level_4: The cast shadow originates from the cube's down-light edge and extends across the paper in the direction opposite the lamp; the contact shadow sits within and roughly matches the cube's base footprint; the cube shows a visible three-value tonal structure (lit face brightest, side face mid-tone, occluded face carrying the core shadow as the darkest value), but the contact shadow reads as a single flat tone rather than fading from dark at the contact line to lighter at its edge, or the cast shadow's outer edge looks noticeably ragged or floats slightly off the paper instead of meeting it cleanly.
level_5: The cast shadow runs continuously along the cube's entire down-light silhouette edge and sits flush against the paper with no visible gap at the contact line; the contact shadow is confined to the cube's base footprint and visibly fades from darkest directly under the cube to lighter at its outer edge; the cube shows a physically coherent three-face value hierarchy (lit face brightest, side face mid-tone, occluded face darkest, carrying the core shadow), and all three values, the cast shadow, and the contact shadow are mutually consistent with a single side-light source.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal violations: the hand jumps to a different position on screen without moving there; the lamp changes position or vanishes; the paper visibly buckles or warps; the cube outline appears or disappears without any drawing motion; the lamp's light flickers or its direction abruptly reverses; the cast shadow or contact shadow jumps to a new spot or vanishes mid-sequence.
level_2: Multiple moderate violations (two or more): the hand lifts completely off the paper partway through drawing the cube or shadows; the lamp visibly rotates or sways during the sequence; the paper surface shows an inconsistent texture (e.g., a glossy patch appears on the otherwise matte sheet); the cast shadow or contact shadow appears before the cube outline is finished; the shadow's position changes independently of the cube's position.
level_3: One minor, isolated inconsistency: e.g., a brief moment where the cast shadow's edge visibly separates from the cube's silhouette before reconnecting; or a short, one-off shimmer on the paper surface unrelated to the lamp; or the hand pauses with the pencil held just above the paper for longer than half a second without contact, but aside from this single lapse, all objects stay in their same relative positions, the lamp's light stays visually consistent, and no part of the drawing warps or breaks apart.
level_4: All objects stay spatially fixed and structurally intact throughout: the hand keeps a consistent pose and contact with the paper while drawing; the desk lamp stays rigidly in its side position; the paper stays flat and undistorted; the completed cube outline stays stable; the cast shadow and contact shadow stay continuously attached to the cube and to each other's expected geometry, but there is one brief, clearly visible wobble in the cast shadow's edge (lasting under a second) or one noticeable brightening/darkening flicker in the contact shadow's tone that a viewer would spot on a single watch-through.
level_5: No visible spatiotemporal discontinuities: the hand moves smoothly and continuously throughout the drawing, keeping steady pencil-to-paper contact; the desk lamp stays perfectly still with no shift in position; the paper keeps a uniform matte look and stays flat; the cube outline appears progressively and never changes once drawn; the cast shadow and contact shadow appear and remain continuously and steadily attached to the cube, with consistent edges and tone from the moment they appear to the end of the shot: no visible wobble, flicker, warping, teleporting, or mismatched timing.