Function fixed_reference_along_pieces 

pub fn fixed_reference_along_pieces(
    rings: &Rings,
    chain: &FixedReferenceChain,
) -> Result<TriMesh, GeomError>

Sweep rings along a planned chain so that every point of the exact surface lies within chain.walls() of the mesh (see the module notes).

Each piece starts from the fixed-reference frame at its own start, never carried across a joint; consecutive pieces share one station, and a loop closes on its first station without caps.