Function pipe_plan 

pub fn pipe_plan(
    pieces: &[PathPiece],
    closed: bool,
    radius: f64,
    inner_radius: Option<f64>,
    fillet_radius: Option<f64>,
    chord: f64,
) -> Result<PipePlan, GeomError>

How swept_disk_along_pieces (closed false) or swept_disk_along_loop (closed true) sweeps these pieces at this budget, refused exactly as they refuse it.