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Kristian Bendiksen
5ee62c61e1
computeFaultDistances faked a nearest-point query with cvf::BoundingBoxTree, which only supports box overlap: it grew a cell-sized box until it overlapped a fault face. For cells far from any fault this did many full tree traversals and then brute-forced the distance to a large, over-collected candidate set, and the answer was only approximate. This was slow on grids with ~10 million cells. The metric is the distance from each cell center to the nearest fault face center, which is exactly a nearest-point search. Replace the bounding-box tree and the grow-the-box loop with a nanoflann KD-tree built over the fault face centers and a single nearest-neighbor query per active cell. A zero-copy adaptor reads the existing std::vector<cvf::Vec3d> directly. The OpenMP loop is retained since nanoflann queries are read-only. The result is O(F log F) build plus O(N log F) queries, the full grid-node array copy is gone, and distances are now exact rather than approximate. Add nanoflann as a vcpkg dependency, wired in like Clipper2 as an imported target. Refs: https://github.com/OPM/ResInsight/issues/14128