Swing bridge

Note: Size at the default params: 8 m long (snapping end to far end), 7.8 m across the banks, and 1.88 m tall at the handrail tops. The deck is 1.6 m wide and 6.15 m long, its walking surface sits at 0.8 m, and the banks are at 0.5 m (the same grass height as canal-and-locks-canal-tiles). The canal between the abutment faces is 3.0 m wide. Its water sits at 0.27 m by default. Snapping: the bridge runs from its snapping end at z = 0 to z = -length, always in whole metres, so it lands on the kit's 1 m grid. The origin is at the snapping end, centred on the deck, at y = 0 (the foot of the abutments and the canal bed). This replaces the library's usual bottom-centre origin, because the brief asks for an end origin on modular pieces. Both end faces are flat. The footprint is asymmetric across the deck: the banks and the canal run 2.24 m out on +X and 5.59 m out on -X, because the deck swings open over the -X bank and lands on a rest block there. Motion: a 12 s seamless loop baked as the clip 'scene-motion'. The deck turns about the vertical king-pin axis at the turntable centre, 2.3 m from the snapping end. The loop goes: swing open, hold open, swing shut, hold closed. It is phased so that t = 0 is mid-swing (45°), which is the thumbnail pose. Only the deck subtree moves (the railings, counterweight and push beam ride on it). The abutments, water and turntable never move. The GLB's static node pose is the t = 2 s frame (fully open), because three-check exports after its determinism seek. Play the clip, or set t = 0, for the thumbnail pose. The GLB has 1,620 triangles in 26 meshes, merged per part and colour, with flat normals baked in (non-indexed). Every material is named exactly after its kit palette colour, and 9 of the 12 kit colours are used (willow, canal green light and boat red and blue dark are not). The exporter writes one material per mesh, so the same colour name appears on several materials: recolour by name. There is no text or signage. The canal water strip is part of the model, because it carries the kit's Water level. Params are baked into the GLB at their defaults and only change geometry when the scene is rebuilt in the viewer. waterLevel (the kit's 'Water level') raises the water from 0.12 m to 0.42 m, and the algae lines follow it. length (7–11 m) widens the canal and lengthens the span. deckWidth (1.2–2.4 m) widens the deck, and the near ramp shortens to stay clear of the heel's swing circle. openAngle (60–95°) sets how far the loop swings the deck, and the rest block moves with it, staying on the bank. Both param extremes passed three-check (7 m / 2.4 m / 95° / water 1 and 11 m / 1.2 m / 60° / water 0). There is a deliberate 0.4 m gap between the near ramp and the deck heel, because the heel needs room to swing. glb-lint: 0 errors. Its verdict is 'UNVERIFIED' only because no requirements contract was supplied. Its 5 heuristic warnings are expected: material count and duplicate materials (from the per-mesh materials), unindexed geometry (flat shading on purpose), sibling overlap (algae and coping skins on the abutments), and detached parts (the deck rests on the king pin in another part, and the ripples float on the water surface). plan-check passes except for its part-id regex, which rejects the hyphens this library's slug-based ids need. The same plan with the slug de-hyphenated passes. three-check accepts those ids, and all 9 survive the GLB reload. Fix rounds: three on the default captures (swing turned away from the hero camera, banks extended under the open deck, far coping width corrected along with the hero framing), plus two fixes found in param-extreme testing (ballast and ramp clearance at a 2.4 m deck, and the rest block kept off the water at 60°).