• Add compile-time product-manifold metrics (SO2, SO3, SE2, SE3, S^N, tori and products) for exact non-Euclidean nearest-neighbor search (C++17, opt out with NANOFLANN_NO_MANIFOLDS). Supported by the static and the incremental KD-trees.
• Tighter block-level pruning bound for SO(3), up to ~28x faster queries on rotation-heavy data.
• Add NANOFLANN_INCREMENTAL_NO_FREELIST (ablation-only) switch.
• Breaking: remove the legacy SO2_Adaptor / SO3_Adaptor metrics, superseded by Manifold_Adaptor. SO(2) and SO(3) now require C++17; C++11 users needing the old metrics should stay on nanoflann 1.x.
• Honor NANOFLANN_NODE_ALIGNMENT > 16 in the node array before C++17 and in PooledAllocator (#321).
• Robustness and performance: reject corrupt vector sizes in load_value(), cheaper post-deletion rebalancing in the incremental index, radius results sorted once in the dynamic adaptor.
• KDTreeEigenMatrixAdaptor now owns its index via std::unique_ptr.
• New examples (SE3, S2, incremental Euclidean and manifold) and tests (Eigen adaptor, radius boundary, incremental manifolds); CI matrix for the compile-time macros.
• Docs: README and Doxygen refresh, clarify that chord_sq_to_angle returns an arc angle.
• Remove dead Travis CI files; add a release helper script.
• Contributors: Jose Luis Blanco-Claraco