CGAL: Add Minkowski sum offset for round corners

[jf---]

Summary

Add MINKOWSKI_ROUND offset method to CGAL geometry module for true round corner offsetting.

Current State

The CGAL module currently only supports STRAIGHT_SKELETON offset method, which produces miter-like corners. The OffsetMethod.MINKOWSKI_ROUND enum exists but throws "not yet implemented".

Technical Challenge

CGAL's approximated_offset_2 requires an exact rational kernel (e.g., Exact_predicates_exact_constructions_kernel with Gmpq), but we're using Exact_predicates_inexact_constructions_kernel for performance.

Options:

1. Use exact kernel for Minkowski operations only (slower but accurate)
2. Use CGAL::offset_polygon_2 with Polygon_offset_builder
3. Approximate with disc polygon for Minkowski sum

Reference

• compas_cgal uses similar approach: https://github.com/compas-dev/compas_cgal
• CGAL docs: https://doc.cgal.org/latest/Minkowski_sum_2/

Files

• bindings/src/cgal_geometry.cpp - implementation needed in offset_polygon_minkowski()
• bindings/src/cgal_geometry.h - OffsetMethod::MINKOWSKI_ROUND already defined

[WangY18]

Thank you very much for your pull request. I am sorry for the delayed response since I missed the pull request. I will go through the pull request carefully and get back to you as soon as possible (maybe in a week).

If my response is still delayed for any reason, please feel free to reach out to me directly via emial at wang-yn22@mails.tsinghua.edu.cn

[WangY18]

I have complete the final binding of python and C++. But I find it too difficult to publish it in Pypi because it involves complex dependence (gurobi and ipopt). So I will keep this "install from source code" version due to the limit of time. Thank you again and welcome for any further PR.

[jf---]

hi @WangY18 I've kept track of your progress, that's been wonderful to see. and yeah your not mistaken, this does complicate things enormously. I tend to use conda which allow to distribute both library + bindings. this does make life a lot easier!
I do think that shipping to pypi should be achievable. let me get back to you.