calibrate-model

Model calibration

Use the inspect-glb skill to measure every unique GLB before mass placement. Rely on dims and groundOffset for contact-accurate placement only when it reports boundsSource: vertices. Store one tuning record per asset:

const ASSET_TUNING = {
    model: {
        boundsSource: 'vertices',
        aabb: { min: [-4, -1, -9], max: [4, 6, 9] },
        dims: [8, 7, 18],
        center: [0, 2.5, 0],
        groundOffset: 1,
        intended: { dimension: 'length', size: 18 },
        scale: 0.9,
        y: 0.9,
        yaw: 180
    }
} as const;

Calculate the record

1. Pick and record the intended dimension and size: character height, building footprint, or vehicle length. Base it on world units or an already calibrated reference model.
2. Calculate scale = intendedSize / measuredDimension.
3. For a floor-resting model, calculate y = groundOffset * scale. Record a deliberate offset for waterlines, embedded objects, or airborne models.
4. Confirm directional facing once in the running app, as the apply-conventions skill describes. PlayCanvas entities face -Z while glTF convention is +Z, but asset packs vary.
5. Retain boundsSource, aabb, dims, center, groundOffset, and the intended size with { scale, y, yaw }. Use the scaled footprint and centre for initial spacing; do not re-derive or add per-instance nudges.

Keep gameplay position and heading on an outer semantic root, and seat the model on one predictable reference point beneath it so a root position means the same thing for every asset: by default the footprint centre over the base. Apply the authored yaw on a wrapper, then the scale and the full offset on the render child inside it, so an off-centre pivot is compensated in the authored frame and never re-rotated by the yaw or by gameplay heading:

const yaw = new Entity('yaw');
yaw.setLocalEulerAngles(0, t.yaw, 0);
const visual = instantiate(asset);
visual.setLocalScale(t.scale, t.scale, t.scale);
visual.setLocalPosition(-t.center[0] * t.scale, t.y, -t.center[2] * t.scale);
yaw.addChild(visual);
root.addChild(yaw);