Domain: Engineering — Optical Engineering
Target concept: Wide-angle lens imaging barrel distortion

Video generation prompt: Place a wide-angle distortion test chart (with a grid) in front of a wide-angle lens (focal length 8 mm), adjust it to achieve a sharp image, and observe the image on the white screen. Barrel distortion is marked with a red curve, the grid is marked with black straight lines, and the distorted area is highlighted in gray.

Evaluation guide:
(i) Target concept: Barrel distortion as a geometric aberration intrinsic to wide-angle lens projection geometry.
Minimum mechanism: A real optical system with finite focal length, projecting a planar grid onto a planar image sensor/screen, where magnification varies radially, requiring no digital post-processing, no synthetic warping, and no non-optical causes (e.g., screen curvature or camera tilt).
(ii)Storyline: Frame 1: Static wide-angle lens visible, centered. Frame 2: Test chart appears in front of lens, fully in view, grid clearly rectilinear in its own plane. Frame 3: White screen appears behind lens, receiving projected image. Frame 4: Focus adjustment completes; central grid lines snap into sharpness. Frame 5: Red curve emerges smoothly along periphery; black lines visibly bulge outward only near edges; gray fills precisely that bulged region. All transitions are synchronous, fixed-viewpoint, and causally ordered: lens + chart + screen → projection → focus → distortion visibility → annotation (red curve + gray). No element appears before its physical prerequisite (e.g., red curve never precedes visible distortion; gray never appears without red curve boundary).

Manual:
Experimental Procedure
1. Position an 8 mm wide-angle lens facing forward.
2. Place a black-grid test chart (square grid on white background) directly in front of the lens, centered on optical axis.
3. Project the lens image onto a plain white screen behind the lens.
4. Adjust focus until grid lines appear sharp.
Observation of Experimental Phenomena
- Black grid lines remain straight only in the central region.
- Black grid lines bend outward toward the image edges (barrel distortion).
- A continuous red curve outlines the distorted peripheral region.
- A gray highlight fills only the area inside the red curve, matching the bent region.
Summary of Experimental Principles
Wide-angle lenses with short focal lengths (e.g., 8 mm) induce barrel distortion due to radial magnification decreasing with distance from optical axis — straight scene lines map to outward-curving image lines.

Prompt Grounding rubric:
level_1: One or more of the seven required elements (wide-angle lens, gridded test chart, white screen, red curve marking, black grid lines, gray highlighted region, or a sharply focused image) is completely absent from the clip.
level_2: Fewer than four of the seven elements (lens, test chart, screen, red curve, black grid lines, gray region, sharp focus) are simultaneously visible and correctly identifiable; the spatial layout is unrecognizable: for example, the chart is not placed in front of the lens, or the screen never receives a projected image.
level_3: All seven elements are simultaneously present in the scene: (1) the wide-angle lens, (2) the gridded test chart placed in front of it, (3) the white screen receiving the projected image, (4) a red curve marking, (5) black straight reference grid lines, (6) a gray-highlighted region, and (7) a sharply focused projected image, arranged on a common optical axis (lens, chart, and screen in a recognizable line) with a fixed camera viewpoint.
level_4: All elements from score 3 are present AND none of the seven elements is occluded, mislabeled, or obscured by extraneous objects (hands, on-screen text, UI overlays); the lens, chart, and screen keep the same relative positions and sizes throughout the clip; the red curve, black grid lines, and gray region each remain a single, clearly identifiable visual element rather than fragmenting or confusingly overlapping with one another.
level_5: All elements from score 4 are present AND the chart itself is never shown physically warped, bent, or pre-distorted before projection (its intrinsic grid stays rectilinear in its own plane); the lens, chart, and screen maintain consistent relative size and alignment across the whole clip with no misregistration, cropping, or extraneous perspective changes applied to the chart's own geometry; no frame introduces a new unrelated object into the scene.

Scientific and Causal Correctness rubric:
level_1: The image on the screen shows no barrel distortion at all, or instead shows pincushion distortion (lines bending inward) or extreme fisheye over-warping; the red curve is drawn around the wrong shape (e.g., an inward-bowing curve, a zigzag, or a curve placed at the center instead of the periphery); the black grid lines are curved in the center and straight at the edges (the reverse of barrel distortion); the gray highlight covers the wrong region or does not appear at all.
level_2: The red curve appears, but in the wrong place (e.g., drawn over the still-straight center, or floating away from the actual image); the black grid lines behave inconsistently (some central lines are curved, some edge lines are straight, with no clear pattern); the gray highlight covers a mismatched region (e.g., the whole screen, or only the corners with gaps in between); the lines appear to converge inward at the edges rather than bulge outward, contradicting barrel distortion.
level_3: The red curve appears only along the outer edge of the image and outlines an outward bulge; the black grid lines stay straight in the middle of the image and visibly bow outward as they approach the frame's edges; the gray highlight appears only in that same peripheral region where the black lines curve; the red curve's outline, the gray region, and the curved black lines all line up with one another spatially.
level_4: All elements from score 3 are present AND the central portion of the image shows no curvature at all in the black lines (they stay visually straight and parallel); the peripheral bowing increases outward with no reversal or S-shaped kink; the red curve forms one smooth, convex outward boundary; the gray highlight is one continuous region with no isolated gaps or islands; no frame shows straight lines at the edge or curved lines in the center.
level_5: All elements from score 4 are present AND the transition from straight (center) to curved (periphery) looks gradual and roughly symmetric all the way around the frame; the red curve forms a single closed loop that visibly matches the outer limit of the visible bulging; the gray region visibly matches the curved, bulging portion of the grid and does not spill into the straight center region; no frame shows the grid lines bending in some other, contradictory way (e.g., squeezed inward on one side while bulging on the other).

Spatiotemporal Consistency rubric:
level_1: The lens, chart, or screen jumps to a different position between frames; the red curve flickers on and off unpredictably; the black grid lines suddenly vanish or jump position mid-clip; the gray region appears or disappears abruptly with no smooth transition; the lighting swings violently (e.g., the scene goes from fully dark to blindingly bright); the camera suddenly rotates or zooms.
level_2: The chart shifts sideways or rotates relative to the lens between frames; the white screen's brightness visibly fluctuates a lot from one frame to the next; the red curve changes its shape or moves position across frames; the black grid lines noticeably jitter in their alignment frame to frame; the gray highlight pulses in and out or breaks into disconnected fragments.
level_3: The lens does not move; the chart stays centered and upright in front of the lens; the white screen stays in place and fully visible; the red curve, black grid lines, and gray region persist continuously across every frame without vanishing, blinking, or drifting out of place; the overall lighting stays steady with no strobing or sudden shadow changes.
level_4: All elements from score 3 are present AND the chart itself never appears physically warped (its own grid stays rectilinear in its own plane, with no artificial pre-distortion applied to the chart object); the red curve and black grid lines stay crisp with no tearing or smearing between frames; the lens, chart, and screen keep the same relative alignment along the optical axis with no unexplained shift in perspective.
level_5: All elements from score 4 are present AND the red curve's two ends visibly stay joined into a closed loop in every frame; the black grid's intersections stay visually consistent from frame to frame (lines don't appear to merge into or split from each other); the gray highlight visibly stays within the red curve's boundary across all frames, without ever appearing to spill outside it or pull back well inside it; there is no visible ghosting, doubling, or smearing of the curve or grid lines between frames.