# discretize.TreeMesh.refine_tetrahedron#

TreeMesh.refine_tetrahedron(self, tetra, levels, finalize=True, diagonal_balance=None)#

Refine the `TreeMesh` along the tetrahedron to the desired level.

Refines the TreeMesh by determining if a cell intersects the given triangle(s) to the prescribed level(s).

Parameters:
tetra(`N`, dim+1, `dim`) array_like

The nodes of the tetrahedron(s).

levels`int` `or` (`N`) array_like `of` `int`

The level to refine intersecting cells to.

finalizebool, `optional`

Whether to finalize after refining

diagonal_balancebool or `None`, `optional`

Whether to balance cells diagonally in the refinement, None implies using the same setting used to instantiate the TreeMesh`.

Examples

We create a simple mesh and refine the TreeMesh such that all cells that intersect the line segment path are at the given levels.

```>>> import discretize
>>> import matplotlib.pyplot as plt
>>> import matplotlib.patches as patches
>>> tree_mesh = discretize.TreeMesh([32, 32, 32])
>>> tree_mesh.max_level
5
```

Next we define the points along the line and the level we want to refine to, and refine the mesh.

```>>> tetra = [
...     [0.32, 0.21, 0.15],
...     [0.82, 0.19, 0.34],
...     [0.14, 0.82, 0.29],
...     [0.32, 0.27, 0.83],
... ]
>>> levels = 5
>>> tree_mesh.refine_tetrahedron(tetra, levels)
```

Now lets look at the mesh, checking how the refine function proceeded.

```>>> levels = tree_mesh.cell_levels_by_index(np.arange(tree_mesh.n_cells))
>>> ax = plt.gca()
>>> tree_mesh.plot_slice(levels, normal='z', slice_loc=0.2, grid=True, ax=ax)
>>> plt.show()
```