Procedural Animation

Animate semantic state, not unrelated transform curves. Define phases,
coordinate frames, velocities, and ownership before writing per-frame updates.

Build order

1. Define the timeline phases and event boundaries.
2. Choose the frame for each motion: world, subject local, orbital radial,

docking axis, or camera shot.

1. Derive target position/orientation from that frame.
2. Use analytic kinematics for authored travel and springs for responsive

convergence.

1. Preserve world transforms when detaching children from a hierarchy.
2. Separate translation, alignment, spin, and secondary debris state.
3. Clamp integration delta and reset every state variable on replay/disposal.

Read references/procedural-motion-and-docking-systems.md
for the launch, staging, docking, debris, spring, quaternion, and
frame-rate-independent response implementations.

Non-negotiable rules

• Use elapsed seconds and deltaSeconds; do not make motion frame-count based.
• Derive orientation from direction/frame, then apply roll or spin as a

separate quaternion.

• Decompose docking error into axial and radial components.
• Switch from spring convergence to an exact terminal pose at the end of a

sequence.

• When reparenting an animated object, capture world position, quaternion, and

scale before removal.

• Use seeded randomness when motion must be reproducible.
• Keep visual shake in a bounded envelope and separate it from trajectory.

Routing boundary

Use $threejs-camera-direction for shot composition and camera handoffs.
Use $threejs-procedural-vfx when the deliverable is primarily plasma, sparks,
or effect pooling rather than object transform motion.