Add ray-box intersection

libs/geom/include/psemek/geom/intersection.hpp

@@ -3,6 +3,8 @@
 #include <psemek/util/empty.hpp>
 
 #include <psemek/geom/simplex.hpp>
+#include <psemek/geom/ray.hpp>
+#include <psemek/geom/box.hpp>
 #include <psemek/geom/orientation.hpp>
 #include <psemek/geom/contains.hpp>
 
@@ -102,4 +104,28 @@ namespace psemek::geom
 		return false;
 	}
 
+	template <typename T, std::size_t N>
+	interval<T> intersection(ray<T, N> const & r, box<T, N> const & b)
+	{
+		auto t = interval<T>::full();
+
+		for (std::size_t i = 0; i < N; ++i)
+		{
+			T tmin = (b[i].min - r.origin[i]) / r.direction[i];
+			T tmax = (b[i].max - r.origin[i]) / r.direction[i];
+
+			if (tmin > tmax) std::swap(tmin, tmax);
+
+			t &= interval<T>{tmin, tmax};
+		}
+
+		return t;
+	}
+
+	template <typename T, std::size_t N>
+	bool intersect(ray<T, N> const & r, box<T, N> const & b)
+	{
+		return !intersection(r, b).empty();
+	}
+
 }