Drawbridge

Note: Size at the default params, at rest (closed): 14 m long (X), 6.04 m deep (Z) across the abutment coping, 7.45 m to the portal finials. The deck is 3.0 m wide at quay height 1.5 m. The near (hinge) abutment is 3 m long, the far one 2 m, and the canal gap between them is 9 m. Fully open (70°), the beam tips reach about 15 m. Snapping: the bridge runs along +X from its snapping end at x = 0 to x = length, always whole metres, so it lands on the kit's 1 m grid. The origin is at the snapping end (x = 0, centred across the depth, y = 0 at the foot of the abutments). 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, so the abutments butt against quay pieces. The side elevation faces +Z, and the canal runs along Z under the leaf. The model has no water, quay or ground. Motion: a 10 s seamless loop (closed hold, raise, open hold, lower, closed hold) baked as the clip 'scene-motion'. The leaf pivots on the hinge axis at the deck-top edge of the near abutment. The balance beams pivot on the portal axle 5 m directly above it, turning by the same angle. Each rod is pinned at its beam tip and counter-rotates, so the linkage is a true parallelogram and the rods hang plumb onto the leaf-tip pins. The abutments, portal, hinges and tide line never move. The GLB's static node pose is the t = 2 s frame (leaf about 14° up), because three-check exports after its determinism seek. That is why glb-lint reports bounds y up to 8.89 m. Play the clip or set t = 0 for the closed rest pose. The GLB has 1,576 triangles in 24 meshes (merged per part and colour), with flat normals baked in (non-indexed). Every material is named exactly after its kit palette colour (9 of the 12 are used). The exporter writes one material per mesh, so the same colour name appears on several materials: recolour by name. There is no text and no signage. 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 green weed band on the abutments from 0.2 m to 0.85 m, always below the leaf girders. It does not add water. length (12–18 m) lengthens the leaf and the beams' front arms together, so the parallelogram holds. deckWidth (2.4–4.0 m) widens the leaf and moves the portal and beams out with it. openAngle (40–75°) sets how far the loop raises the leaf. Clearances (counterweights outside the posts, the leaf never behind its hinge face) were worked out for the full 0–75° range, but only the default params were captured. glb-lint: 0 errors and 6 heuristic warnings: material count and duplicate materials (from the per-mesh materials), unindexed geometry (flat shading on purpose), sibling overlap (plinths under posts, the axle through the posts), detached parts (the hinge barrels, wet line and rods are seated on or into other parts, not floating), and scale (compared with the direction's 1 m reference). 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.