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feat: snap implicit cuts to existing vertices, add does_self_intersect #25

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Merged
lachlangrose merged 1 commit into from
Sep 28, 2026
Merged

feat: snap implicit cuts to existing vertices, add does_self_intersect #25

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7 changes: 6 additions & 1 deletion .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -44,4 +44,9 @@ loop_cgal/__pycache__/__init__.cpython-311.pyc
build/*
*.vtk
*.ply
build_win64/*
build_win64/*

# Local import shim: symlinks __init__.py / utils.py / build/_loop_cgal.so into
# one directory so `PYTHONPATH=.local-shim` imports the locally built extension.
# Needed because the source `loop_cgal/` package has no .so and shadows the build.
.local-shim/
40 changes: 35 additions & 5 deletions loop_cgal/bindings.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,14 @@ PYBIND11_MODULE(_loop_cgal, m)
.value("KEEP_POSITIVE_SIDE", ImplicitCutMode::KEEP_POSITIVE_SIDE)
.value("KEEP_NEGATIVE_SIDE", ImplicitCutMode::KEEP_NEGATIVE_SIDE)
.export_values();
py::class_<TriMesh>(m, "TriMesh")
py::class_<TriMesh>(m, "TriMesh",
"A CGAL surface mesh of triangles.\n\n"
"NOT THREAD-SAFE. Most methods release the GIL for the duration of the "
"CGAL call, so two Python threads touching the same TriMesh concurrently "
"are a data race in C++ -- corrupt memory, not merely a wrong answer. That "
"includes passing one mesh as the `other`/`surface` argument of a call "
"running on another thread. Give each thread its own meshes, or serialise "
"access yourself. Separate processes (the usual pattern here) are unaffected.")
.def(py::init<const pybind11::array_t<double> &, const pybind11::array_t<int> &>(),
py::arg("vertices"), py::arg("triangles"))
.def(py::init([](const TriMesh& other) { return other.clone(); }),
Expand All @@ -28,13 +35,16 @@ PYBIND11_MODULE(_loop_cgal, m)
.def("clip_with_plane", &TriMesh::clipWithPlane,
py::arg("a"), py::arg("b"), py::arg("c"), py::arg("d"),
py::arg("use_exact_kernel") = true,
py::call_guard<py::gil_scoped_release>(),
"Clip the mesh with the halfspace ax+by+cz+d <= 0. "
"Uses PMP::clip(mesh, Plane_3) directly — no corefinement, no skirt construction. "
"Returns the number of faces removed (0 = no-op).")
.def("corefine", &TriMesh::corefine, py::arg("other"),
py::arg("use_exact_kernel") = true,
py::call_guard<py::gil_scoped_release>(),
"Corefine this mesh with another, inserting the shared intersection "
"polyline into BOTH meshes in place. After the call the two meshes "
"polyline into BOTH meshes in place. NOTE this MUTATES `other` as well "
"as self, so `other` must not be shared with a concurrent call. After the call the two meshes "
"carry coincident vertices/edges along the intersection curve, so "
"patches taken from each side stitch together watertight. "
"Returns the number of vertices added to this mesh. "
Expand All @@ -44,23 +54,31 @@ PYBIND11_MODULE(_loop_cgal, m)
py::arg("preserve_intersection") = false,
py::arg("preserve_intersection_clipper") = false,
py::arg("use_exact_kernel") = true,
py::arg("extend") = true,
py::call_guard<py::gil_scoped_release>(),
"Cut mesh with a clipper surface. Returns the number of faces removed "
"(0 indicates the clipper did not intersect or did not extend beyond the mesh).")
"(0 indicates the clipper did not intersect or did not extend beyond the mesh). "
"extend=True grows a skirt so a small clipper cuts all the way through; pass "
"extend=False when the clipper already spans the domain. "
"Mutates self and reads `surface`; neither may be touched by a concurrent call.")
.def("remesh", &TriMesh::remesh, py::arg("split_long_edges") = true,
py::arg("target_edge_length") = 10.0,
py::arg("number_of_iterations") = 3,
py::arg("protect_constraints") = true,
py::arg("relax_constraints") = false)
py::arg("relax_constraints") = false,
py::call_guard<py::gil_scoped_release>())
.def("save", &TriMesh::save, py::arg("area_threshold") = 1e-6,
py::arg("duplicate_vertex_threshold") = 1e-6)
.def("reverse_face_orientation", &TriMesh::reverseFaceOrientation,
"Reverse the face orientation of the mesh.")
.def("add_fixed_edges", &TriMesh::add_fixed_edges,
py::arg("pairs"),
py::call_guard<py::gil_scoped_release>(),
"Vertex index pairs defining edges to be fixed in mesh when remeshing.")
.def("cut_with_implicit_function", &TriMesh::cut_with_implicit_function,
py::arg("property"), py::arg("value"),py::arg("cutmode") = ImplicitCutMode::KEEP_POSITIVE_SIDE,
py::arg("snap_tol") = 1e-4,
py::call_guard<py::gil_scoped_release>(),
"Cut the mesh with an implicit function defined by vertex properties. "
"snap_tol reuses an existing vertex when a crossing lands within that "
"fraction of an edge from it, preventing sliver triangles (0 = disable).")
Expand All @@ -69,7 +87,19 @@ PYBIND11_MODULE(_loop_cgal, m)
.def("_cgal_n_vertices", &TriMesh::n_vertices, "Number of vertices in the CGAL mesh.")
.def("_cgal_points", &TriMesh::get_points, "Vertex coordinates as (n, 3) numpy array.")
.def("overlaps", &TriMesh::overlaps, py::arg("other"), py::arg("bbox_tol") = 1e-6,
"Return True if this mesh intersects another TriMesh (AABB fast-reject + triangle-level check).")
py::call_guard<py::gil_scoped_release>(),
"Return True if this mesh intersects another TriMesh (AABB fast-reject + triangle-level check). "
"Reads both meshes; neither may be mutated by a concurrent call.")
.def("does_self_intersect", &TriMesh::does_self_intersect,
py::call_guard<py::gil_scoped_release>(),
"Return True if the mesh intersects itself.\n\n"
"Wraps CGAL PMP::does_self_intersect. A self-intersecting surface is "
"outside the domain of the boolean operations - corefine, cut_with_surface "
"and the clip paths may fail or return a corrupt result on one - so this is "
"the check to run before handing a mesh to them, and after a remesh or a fit "
"that could have folded it.\n\n"
"Cost is O(n log n) via an AABB tree over the faces: cheap enough to assert "
"on, not free in a tight loop.")
.def("clone", &TriMesh::clone,
"Return a deep copy of this TriMesh at the C++ level (no pyvista round-trip). "
"Preserves the full fixed-edge set including any user-added edges.")
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