FSClipping

FSClipping is a C++20 library that clips two meshes against each other at a shared boundary. It is built on the FSDM data-management framework.

Given two meshes and one boundary marker on each, it computes the intersection of the two boundary face sets. It then builds a new clipped mesh for each side, so both meshes conform to a common interface. It is used for non-conforming mesh coupling in CFD, such as sliding or chimera interfaces.

Features

• Sutherland–Hodgman polygon clipping of boundary faces, with BVH-accelerated candidate search.
• Volume reconstruction: cells next to the interface become polyhedral cells that conform to the clipped faces.
• MPI-parallel execution on distributed meshes.
• Integrates with FSDM as a FSDataManager operation (ClippedMesh), with Python bindings (SWIG).

Requirements

• CMake ≥ 3.20
• A C++20 compiler
• MPI (OpenMPI ≥ 4.0)
• FSDM ≥ 25.08 (found through pkg-config)
• Python ≥ 3.10 with development headers
• SWIG (for the Python bindings)

Build

cmake -S . -B build -DCMAKE_INSTALL_PREFIX=/path/to/install
cmake --build build -j
cmake --install build

Tests

The tests use GoogleTest (bundled in thirdparty/) and are on by default (BUILD_TESTING=ON).

cd build
ctest --output-on-failure

The sequential tests run on 1 MPI process. The parallel tests run on 3, 5 or 6 processes and are prefixed np3., np5. and np6..

Usage (Python)

The clipping runs on 1 + n1 + n2 MPI processes: one process does the matching, n1 processes hold mesh 1 and n2 processes hold mesh 2.

dataManagerOps = (("ClippedMesh", {"MeshKeyOrig1"    : "original1",
                                   "MeshKeyOrig2"    : "original2",
                                   "MeshKeyClipped1" : "clippedMesh1",
                                   "MeshKeyClipped2" : "clippedMesh2",
                                   "ClippedMarker1"  : 1,
                                   "ClippedMarker2"  : 1,
                                   "Tolerance"       : 1e-8}),)
dm.DoOps(dataManagerOps) or FSError.PrintAndExit()

Parameter	Description
MeshKeyOrig1, MeshKeyOrig2	Keys of the input meshes in the data manager
MeshKeyClipped1, MeshKeyClipped2	Keys of the output clipped meshes
ClippedMarker1, ClippedMarker2	Boundary marker that selects the faces to clip on each mesh
Tolerance	Geometric tolerance of the clipping (a length)

For a complete example, including mesh loading and the MPI setup, see example/meshOp/howToComputeClippedMesh.py.

Project layout

include/FSClipping/   Public headers
src/                  Library sources
py/                   Python bindings (SWIG)
test/                 Unit tests and test meshes
example/              Python examples
tools/                pkg-config template

License

FSClipping is distributed under the GNU Lesser General Public License v3.0. See LICENSE.