version: "1.0.0" name: assemble-scene description: Use when composing PlayCanvas entity hierarchies from models, colliders, rigid bodies, and scripts, so each object has one semantic root and clear lifecycle.

Scene assembly

Each scene object has one named root. Put position, heading, rigidbody, collision, and scripts on the root, and the calibrated visual from calibrate-model below it. Apply calibration once; if the tuning record is missing, calibrate first.

• Name roots by role, with predictable names for repeated instances.
• Size colliders from measured bounds and keep them aligned with render bounds.
• Space roots by the scaled footprint in the tuning record, not by pivot position. A non-90° yaw

rotates the footprint, so reserve its larger horizontal extent.

• Keep UI, effects, cameras, and lights outside model hierarchies.
• Remove the root through its surface's lifecycle and unregister events it owns.
• Rigid bodies need Ammo loaded first (build-app).

Check placement

After a rendered frame, measure each support or attachment at the object's actual position, using a mount point, raycast, or geometry sample read through inspect-runtime. A positive gap floats; a negative gap penetrates. Overlapping world AABBs between unrelated roots are a failure unless two different views prove the overlap is empty space.

Read only the reference matching the code: direct Engine, React, or Web Components.