Function laplacian_unwrap_fft_padded 

fn laplacian_unwrap_fft_padded(
    phase: &[f64],
    grid: &Grid,
    pad: [usize; 3],
) -> Vec<f64>

Schofield & Zhu sin/cos unwrapping on the zero-padded volume (STI Suite’s MRPhaseUnwrap). Returns the whole volume, unmasked.