Add preserve_border option to simplify and simplify_mesh (#89) - #94
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Add an optional `preserve_border` flag that protects the open boundary of a mesh during decimation by skipping the collapse of any edge that touches a border vertex. It is threaded through both the standard (`simplify_mesh`) and lossless (`simplify_mesh_lossless`) paths in the core header, the Cython wrapper, and the Python array/PyVista APIs. This mirrors pyfqmr PR #37, which added border preservation only to the lossless method; here it is available on both paths. Closes #89 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Summary
Adds an optional
preserve_borderflag (defaultFalse) that preserves the open boundary of a mesh during decimation, addressing #89.When
preserve_border=True, any edge that touches an open-border vertex is skipped, so the perimeter of an open mesh is retained exactly instead of being eroded by collapses.What changed
The flag is threaded through the whole stack:
fast_simplification/Simplify.h—simplify_meshandsimplify_mesh_losslesseach take a newbool preserve_border=false. The existing border check is generalized: withpreserve_borderit skips a collapse if either endpoint is a border vertex; otherwise it keeps the originalv0.border != v1.borderbehaviour.fast_simplification/_simplify.pyx— extern declarations and thesimplify/simplify_losslesswrappers pass the flag through.fast_simplification/simplify.py—simplify(...)(array API) andsimplify_mesh(...)(PyVista API) gain a documentedpreserve_borderkeyword, threaded through both the standard and lossless branches.Unlike pyfqmr PR #37 (Kramer84/pyfqmr-Fast-Quadric-Mesh-Reduction#37), which applied border preservation only to the lossless method, this applies it to both the standard and lossless paths.
Test
A new
test_preserve_borderdecimates a triangulatedpv.Plane(80 boundary points) at 90% reduction:preserve_border=Falseerodes the boundary (80 → 15 points);preserve_border=Truekeeps all 80.preserve_border=Falsecollapses the boundary (80 → 3 points);preserve_border=Truekeeps all 80.Full existing suite still passes (12 passed).
Closes #89
🤖 Generated with Claude Opus 4.8 (Claude Code)