Request: build one tube chunk. positions is transferred (main thread keeps its own copy).
positions
Segments in the chunk.
Correlates the response; the pool also uses it to place the result in deterministic chunk order.
Optional
Interleaved segment endpoints (x0,y0,z0,x1,y1,z1 per segment) — the transferable payload.
Request: build one tube chunk.
positionsis transferred (main thread keeps its own copy).