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.
3. Derive target position/orientation from that frame.
4. Use analytic kinematics for authored travel and springs for responsive convergence.
5. Preserve world transforms when detaching children from a hierarchy.
6. Separate translation, alignment, spin, and secondary debris state.
7. 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.