Implement TrapezoidalDecomposer::decompose using sweep-line algorithm
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tigercosmos
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tigercosmos
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Feb 2, 2026
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| return {begin_index, end_index}; | ||
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| std::pair<size_t, size_t> decompose(size_t polygon_id, std::vector<point_type> const & points); |
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Separate the implementation below.
tigercosmos
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Feb 2, 2026
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| if (m_trapezoids->ndim() == 3) | ||
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| edge.z_at_lower_y = p1.z(); | ||
| edge.dzdy = (p2.z() - p1.z()) / (p2.y() - p1.y()); |
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Since Z is still TODO, not sure if we should throw.
tigercosmos
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Feb 2, 2026
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| size_t const begin_index = m_trapezoids->size(); | ||
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| std::map<value_type, SweepEvent> events; // y-value to events starting at that y |
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New implementation starting from here.
tigercosmos
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Feb 2, 2026
| m_trapezoids->append(lower_x0, y_current, lower_x1, y_current, upper_x1, y_next, upper_x0, y_next); | ||
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| } | ||
| } |
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New implementation ending here.
tigercosmos
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Feb 2, 2026
| std::vector<Edge> active_edges; | ||
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| // Sweep from bottom to top | ||
| for (size_t i = 0; i < y_values.size() - 1; ++i) |
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From buttom to the top, sweeping the line one by one with each unique y value.
tigercosmos
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Feb 2, 2026
| return {begin_index, begin_index}; | ||
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| std::vector<Edge> active_edges; |
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Active edges are the edges that bound the current trapezoidal region.
tigercosmos
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Feb 2, 2026
| namespace modmesh | ||
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| TEST(TrapezoidalDecomposer, simple_rectangle) |
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All the cases are generated by AI and are manually checked and modified.
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@yungyuc Please help review the PR, thank you! |
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Implemented TrapezoidalDecomposer::decompose using a sweep-line approach and added test cases in gtest.
AI usage: Copilot + Claude 4.5 generating the test cases, VSCode IntelliSense for auto-completion, ChatGPT 5.2 for discussing the algorithm.