Add Tolerances to 2D Search and begin 3D Search Implementation

[matthew-mccall]

This pull request refactors and generalizes the point search functionality in the codebase, with a focus on updating the 2D search to use new class and type names, improving the search result logic, and adding support for higher dimensions. The changes also introduce new functors and intersection map constructors for both 2D and 3D cases, and update the interfaces and result handling to use more descriptive and robust structures.

Refactoring and Generalization of Point Search:

• Replaced GridPointSearch and related types with GridPointSearch2D and associated result types throughout the codebase, updating construction and usage to use std::unique_ptr and new class names (OmegaHField, adj_search.hpp, point_search.cpp). [1] [2] [3] [4] [5]
• Updated the result logic in the point search operator to distinguish between vertex, edge, and face hits, using tolerances for proximity checks, and storing the nearest element ID and parametric coordinates. The result struct and dimensionality enum were updated for clarity. [1] [2]

Support for Higher Dimensions:

• Added generic bounding box and intersection routines (simplex_bbox, within_bbox, simplex_intersects_bbox, bbox_verts_within_simplex) templated by dimension, enabling use for both 2D and 3D meshes. [1] [2] [3] [4]

New Functors and Intersection Map Constructors:

• Introduced GridTriIntersectionFunctor2D and GridTriIntersectionFunctor3D for mesh/grid intersection logic, with corresponding construct_intersection_map_2d and construct_intersection_map_3d functions for building candidate maps in 2D and 3D. [1] [2]

Interface and Type Updates:

• Updated interfaces and result handling in search-related classes and functions to use new types and enums, and replaced deprecated or custom barycentric calculations with calls to Omega_h::barycentric_from_global. [1] [2]

These changes modernize the point search infrastructure, enable future extension to higher dimensions, and improve the clarity and reliability of search results.

[jacobmerson]

Note: this was moved here from jacobmerson#11 . Some preliminary discussion happened there.

[jacobmerson]

@matthew-mccall at least the initial CI test failures should be resolved from this PR: #216

[Copilot]

Pull Request Overview

This pull request refactors the point search functionality to support both 2D and 3D meshes, introducing a class hierarchy with PointLocalizationSearch as a base class and dimension-specific implementations (GridPointSearch2D and GridPointSearch3D). The changes add tolerance-based proximity checking for vertices and edges in 2D, generalize bounding box routines to work with arbitrary dimensions, and lay the groundwork for 3D point localization.

• Refactored GridPointSearch to GridPointSearch2D with a new base class PointLocalizationSearch<dim>
• Added tolerance-based searching for vertices and edges in 2D with configurable proximity thresholds
• Introduced GridPointSearch3D with basic region containment checking (without tolerance support yet)

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
test/test_point_search.cpp	Updated tests to use new GridPointSearch2D API, added tolerance configuration, and updated test expectations for vertex/edge/face classification
src/pcms/uniform_grid.h	Removed default template parameter from UniformGrid and added explicit Uniform3DGrid typedef
src/pcms/point_search.h	Introduced PointLocalizationSearch<dim> base class, split into GridPointSearch2D and GridPointSearch3D derived classes with tolerance support
src/pcms/point_search.cpp	Refactored 2D search with tolerance-based vertex/edge detection, added dimension-agnostic helper functions (simplex_bbox, within_bbox, bbox_verts_within_simplex), and implemented basic 3D search
src/pcms/adapter/omega_h/omega_h_field.h	Changed from std::optional<GridPointSearch> to std::unique_ptr<PointLocalizationSearch2D> for polymorphism
src/pcms/interpolator/adj_search.hpp	Updated to use GridPointSearch2D and renamed tri_id to element_id

Comments suppressed due to low confidence (1)

src/pcms/point_search.cpp:660

• In 3D, Omega_h::FACE refers to triangular faces of tetrahedra, not the tetrahedral elements themselves. For 3D point search, you likely want connectivity from regions (tetrahedra) to faces/edges/vertices. The current code queries face-to-edge and face-to-vertex adjacency, which may not be the intended behavior for locating points within tetrahedral elements. Consider using Omega_h::REGION instead of Omega_h::FACE for the 3D case.

  tris2edges_adj_ = mesh.ask_down(Omega_h::FACE, Omega_h::EDGE);
  tris2verts_adj_ = mesh.ask_down(Omega_h::FACE, Omega_h::VERT);
  edges2verts_adj_ = mesh.ask_down(Omega_h::EDGE, Omega_h::VERT);

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The variable nearest_element_id is initialized to candidates_begin, which is an index into the candidate map, not an actual element ID. If no elements are found within tolerance or inside the mesh, this will result in returning an incorrect element ID. Consider initializing to -1 or 0 to indicate "not found", and only update it when a valid element is identified.

Suggested change

	auto nearest_element_id = candidates_begin;
	auto nearest_element_id = -1;

[Copilot]

Same issue as line 435 in 2D: nearest_triangle is initialized to candidates_begin, which is an index into the row map, not an actual element ID. If no tetrahedron contains the point, this will return an incorrect negative element ID derived from the wrong value. Initialize to -1 or ensure it's set to a valid element ID before use.

[Copilot]

The initial dimensionality is set to REGION, which is a 3D concept (tetrahedron). In 2D, this should be initialized to a more appropriate value. Since the search prioritizes vertex → edge → face in that order, and we're looking for the nearest element, consider initializing to FACE (the highest dimensionality in 2D) or keeping track of whether any element was found at all.

Suggested change

	auto dimensionality = GridPointSearch2D::Result::Dimensionality::REGION;
	auto dimensionality = GridPointSearch2D::Result::Dimensionality::FACE;

[jacobmerson]

This PR is blocked by #227 because we need to test on the GPU.