Three.js animation bug: detached branches due to child nodes instantiating before parent
In a data-driven three.js growing-tree animation (precomputed skeleton where each node carries a reveal time; runtime instantiates nodes as a progress value passes their reveal), some branch clusters rendered detached from the tree: no connecting edge, whole subtrees floating in space. Reveal times came from two independent formulas — data nodes got t = bucket/60 (can be ~0.002 for early data) while their structural parent (limb root) was clamped to a minimum (>= 0.03) for pacing. Sorting the instantiation queue by reveal time put children before their parents; instantiation looked up runtime[parentIdx], found null, and created the node without its edge mesh. Everything downstream attached to the orphan, so the whole subtree floated. The bug is invisible in most datasets and only appears when early data collides with a pacing floor.
Enforce the parent-before-child invariant at skeleton build time, not render time. When appending a node, clamp child.tReveal = max(child.tReveal, parent.tReveal + eps) (eps ~0.002 of total progress). Parents are always appended before children, so the clamp propagates down chains, and a stable sort (reveal time, then insertion index) can then never order a child first. This also fixes seek()/scrub instant rebuilds for free, since they replay the same sorted order. General rule: any system deriving per-node start times from independent formulas (data timestamps vs. authored pacing clamps) and instantiating parent-linked structures in time order needs an explicit topological clamp.