discretize 0.13.0 Release Notes

October 15, 2026

This minor release adds a few new mesh utilities, extends the surface inner product matrices to more mesh types, fixes several bugs, and moves to a smaller set of wheels for new Python versions.

Python versions

discretize has bumped its minimum supported python version to 3.12 (and numpy to 1.26), and is tested against versions 3.12-3.15. Users on older python versions should continue to use discretize 0.12.x.

Wheels

Wheels for GIL-enabled python are now built against the limited API (abi3), so a single wheel per platform covers every python version from 3.12 on. This means new wheels are available as soon as a new python version is released, without waiting on a new discretize release. The free-threaded builds (3.14t and 3.15t) are still built as separate per-version wheels.

Mesh slicing

A new discretize.utils.slice_mesh() utility extracts an axis-aligned 2D slice of a 3D TensorMesh or TreeMesh, returning a 2D mesh of the same type. It can also return the index of the 3D cell that each 2D cell came from (with return_indices=True), which makes it easy to take a model from the 3D mesh onto the slice. plot_slice now uses it internally.

TreeMesh updates

discretize.TreeMesh.refine_surface() has a new extrapolate_surface keyword that changes how the surface is padded horizontally. Currently the point cloud is stretched about its center, which distorts the surface when it is not centered or convex. With extrapolate_surface=True the surface is instead extended outward from every node along its boundary, which is a nearest neighbor extrapolation of the surface. The extension step is also available on its own as discretize.utils.extend_surface_boundary(), which is useful for selecting the cells intersected by the padded surface.

Attention

In discretize 1.0 extrapolate_surface=True will become the default. For now the old behavior is kept, and a FutureWarning is issued when horizontal padding is requested without setting extrapolate_surface.

Inner products

Edge inner product matrices over surfaces (get_edge_inner_product_surface and its derivative) are now implemented for CurvilinearMesh and SimplexMesh, in both 2D and 3D.

Bugfixes

• Fixed zeros_outside=True skipping the interpolation of locations that were inside the mesh for TreeMesh.

• Fixed discretize.TreeMesh.insert_cells() (and refine_points()) when given multiple points with a single level.

• Fixed discretize.TreeMesh.average_cell_to_face() for cells that span the whole mesh.

• Fixed an out-of-bounds read when volume averaging between two TreeMesh objects (discretize.utils.volume_average()), which could occasionally cause a segmentation fault.

Contributors

• @jcapriot

• @santisoler

• @dccowan

Pull requests

• Fix logic error when zeros_outside was True by @jcapriot in #410

• Hierarchical inner products for unstructured meshes by @dccowan in #412

• Maintenance on build/testing scripts by @jcapriot in #413

• Fix bug in mesh refinement with multiple points by @santisoler in #416

• Bump minimum version and start testing on 3.15 by @jcapriot in #417

• Test out using uv instead of conda for a testing by @jcapriot in #418

• Abi3 wheels by @jcapriot in #419

• Add slice_tree_mesh utility for axis-aligned TreeMesh slices by @jcapriot in #420

• Fix TreeMesh average_cell_to_face for cells spanning the whole mesh by @jcapriot in #421

• Make refine_surface not distort the point cloud to handle horizontal extensions. by @jcapriot in #422