Bossens-Heckbert smoothing

[nschloe]

Fixes #85.

[krober10nd]

for the scaling of the target_lengths I like to use the ratio of the medians as it represents the inflation factor better in domains with large disparities in mesh size than the ratio of squares.

# Bossen-Heckbert
def _compute_forces(p, t, fh, min_edge_length, L0mult):
    """Compute the forces on each edge based on the sizing function"""
    N = p.shape[0]
    bars = _get_bars(t)
    barvec = p[bars[:, 0]] - p[bars[:, 1]]  # List of bar vectors
    L = np.sqrt((barvec ** 2).sum(1))  # L = Bar lengths
    L[L == 0] = np.finfo(float).eps
    hbars = fh(p[bars].sum(1) / 2)
    # this line is what I'm referring to in my comment above.
    L0 = hbars * L0mult * (np.nanmedian(L) / np.nanmedian(hbars))
    LN = L / L0
    F = (1 - LN ** 4) * np.exp(-(LN ** 4)) / LN
    Fvec = (
        F[:, None] / LN[:, None].dot(np.ones((1, 2))) * barvec
    )  # Bar forces (x,y components)
    Ftot = _dense(
        bars[:, [0] * 2 + [1] * 2],
        np.repeat([list(range(2)) * 2], len(F), axis=0),
        np.hstack((Fvec, -Fvec)),
        shape=(N, 2),
    )
    return Ftot

[nschloe]

Interesting. I'll add a separate issue for this.

[nschloe]

Is this code in SeismicMesh?

[krober10nd]

Yea, I was doing it offline. Now I just uploaded some quick implementation in there in krober10nd/SeismicMesh#226

Ideally it should go in maybe as an option. I haven't explored 3D yet.