Add intersects ellipse-box

Author: aprokop

src/geometry/algorithms/ArborX_Intersects.hpp

@@ -14,6 +14,7 @@
 #include "ArborX_Distance.hpp"
 #include "ArborX_Expand.hpp"
 #include <ArborX_GeometryTraits.hpp>
+#include <ArborX_Segment.hpp>
 #include <misc/ArborX_Vector.hpp>
 
 #include <Kokkos_Array.hpp>
@@ -577,7 +578,7 @@ struct intersects<EllipsoidTag, SegmentTag, Ellipsoid, Segment>
 
     // At^2 + 2B^t + C
     auto A = rmt_multiply(ab, rmt, ab);
-    auto B = rmt_multiply(ab, rmt, ca);
+    auto B = rmt_multiply(ca, rmt, ab);
     auto C = rmt_multiply(ca, rmt, ca);
     auto t = -B / A;
 
@@ -598,6 +599,39 @@ struct intersects<SegmentTag, EllipsoidTag, Segment, Ellipsoid>
   }
 };
 
+template <typename Ellipsoid, typename Box>
+struct intersects<EllipsoidTag, BoxTag, Ellipsoid, Box>
+{
+  KOKKOS_FUNCTION static constexpr bool apply(Ellipsoid const &ellipsoid,
+                                              Box const &box)
+  {
+    static_assert(GeometryTraits::dimension_v<Box> == 2,
+                  "Ellipsoid-box intersection is only implemented for 2D");
+
+    auto min_corner = box.minCorner();
+    auto max_corner = box.maxCorner();
+    using ::ArborX::Experimental::Segment;
+    // clang-format off
+    return
+      Details::intersects(ellipsoid.centroid(), box) ||
+      Details::intersects(ellipsoid, Segment{min_corner, {min_corner[0], max_corner[1]}}) ||
+      Details::intersects(ellipsoid, Segment{min_corner, {max_corner[0], min_corner[1]}}) ||
+      Details::intersects(ellipsoid, Segment{max_corner, {min_corner[0], max_corner[1]}}) ||
+      Details::intersects(ellipsoid, Segment{max_corner, {max_corner[0], min_corner[1]}});
+    // clang-format on
+  }
+};
+
+template <typename Box, typename Ellipsoid>
+struct intersects<BoxTag, EllipsoidTag, Box, Ellipsoid>
+{
+  KOKKOS_FUNCTION static constexpr bool apply(Box const &box,
+                                              Ellipsoid const &ellipsoid)
+  {
+    return Details::intersects(ellipsoid, box);
+  }
+};
+
 } // namespace Dispatch
 
 } // namespace ArborX::Details

test/tstDetailsAlgorithms.cpp

@@ -343,7 +343,7 @@ BOOST_AUTO_TEST_CASE(intersects)
   BOOST_TEST(intersects(box2, Segment2{{-1, 2}, {2, -1}}));
   BOOST_TEST(!intersects(Segment2{{0.5, 1.6}, {2, 0}}, box2));
 
-  // ellipsoid
+  // ellipsoid [2x^2 - 3xy + 2y^2 <= 1]
   using Ellipse = ArborX::Experimental::Ellipsoid<2>;
   constexpr Ellipse ellipse{{1.f, 1.f}, {{2.f, -1.5f}, {-1.5f, 2.f}}};
   BOOST_TEST(intersects(ellipse, Point2{1.f, 1.f}));
@@ -364,6 +364,20 @@ BOOST_AUTO_TEST_CASE(intersects)
   BOOST_TEST(intersects(ellipse, Segment2{{0.5, 0.5}, {1.5, 1.5}}));
   BOOST_TEST(intersects(ellipse, Segment2{{0.0, 1.9}, {3.0, 1.9}}));
   BOOST_TEST(!intersects(ellipse, Segment2{{2.1, 0}, {2.1, 3}}));
+
+  using Box2 = ArborX::Box<2>;
+  BOOST_TEST(intersects(ellipse, Box2{{-10, -10}, {10, 10}}));
+  BOOST_TEST(intersects(ellipse, Box2{{0.5, 0.5}, {1.0, 1.0}}));
+  BOOST_TEST(intersects(ellipse, Box2{{-1, -1}, {0, 0}}));
+  BOOST_TEST(intersects(ellipse, Box2{{2, 2}, {3, 3}}));
+  BOOST_TEST(intersects(ellipse, Box2{{-1, -1}, {0, 2}}));
+  BOOST_TEST(intersects(ellipse, Box2{{-1, -1}, {2, 0}}));
+  BOOST_TEST(intersects(ellipse, Box2{{2, 1}, {3, 3}}));
+  BOOST_TEST(intersects(ellipse, Box2{{1, 2}, {3, 3}}));
+  BOOST_TEST(!intersects(ellipse, Box2{{1.5, 0}, {2, 0.5}}));
+  BOOST_TEST(!intersects(ellipse, Box2{{-1, -1}, {-0.1, -0.1}}));
+  BOOST_TEST(!intersects(ellipse, Box2{{0, 1.5}, {0.5, 2}}));
+  BOOST_TEST(!intersects(ellipse, Box2{{2.1, 2.1}, {3, 3}}));
 }
 
 BOOST_AUTO_TEST_CASE(equals)