# Flat triangular mesh
graph = create_all_graph_components(
    coords=xy,
    m2m_connectivity="flat",
    m2m_connectivity_kwargs=dict(mesh_node_distance=3.0),
    mesh_layout="triangular",
    ...
)

# Hierarchical triangular mesh
graph = create_all_graph_components(
    coords=xy,
    m2m_connectivity="hierarchical",
    m2m_connectivity_kwargs=dict(mesh_node_distance=3.0, max_num_levels=3),
    mesh_layout="triangular",
    ...
)

def create_single_level_2d_triangular_mesh_graph(xy, nx, ny):
    """
    Create directed graph with triangular lattice topology.
    Uses networkx.triangular_lattice_graph which produces offset rows
    with equilateral triangle side length 1 and row spacing sqrt(3)/2.
    """
    xm, xM = np.amin(xy[:, 0]), np.amax(xy[:, 0])
    ym, yM = np.amin(xy[:, 1]), np.amax(xy[:, 1])

    dx = (xM - xm) / nx
    dy = (yM - ym) / ny

    g = networkx.triangular_lattice_graph(ny, nx, with_positions=True)

    # Scale and offset positions to cover the domain
    for node in g.nodes:
        pos = np.array(g.nodes[node]["pos"])
        # Scale from unit triangles to domain
        g.nodes[node]["pos"] = np.array([
            xm + dx/2 + pos[0] * dx,
            ym + dy/2 + pos[1] * dy
        ])
        g.nodes[node]["type"] = "mesh"

    # Convert to DiGraph with bidirectional edges
    dg = networkx.DiGraph(g)
    for u, v in g.edges():
        d = np.sqrt(np.sum((dg.nodes[u]["pos"] - dg.nodes[v]["pos"]) ** 2))
        dg.edges[u, v]["len"] = d
        dg.edges[u, v]["vdiff"] = dg.nodes[u]["pos"] - dg.nodes[v]["pos"]
        dg.add_edge(v, u)
        dg.edges[v, u]["len"] = d
        dg.edges[v, u]["vdiff"] = dg.nodes[v]["pos"] - dg.nodes[u]["pos"]

    return dg

nx = int(range_x / mesh_node_distance)
ny = int(range_y / (mesh_node_distance * np.sqrt(3) / 2))

if graph_crs is not None and graph_crs.is_geographic and mesh_layout == "triangular":
    warnings.warn(
        "mesh_layout='triangular' produces non-uniform physical spacing in "
        "geographic coordinates. Consider mesh_layout='icosahedral' for "
        "uniform coverage on a sphere."
    )