From b4584f758d8eef4165b5dfff83f98b364b5f2b71 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Mon, 21 Feb 2022 13:05:35 +0300
Subject: [PATCH] Add segment-sphere intersection

---
 .../geom/include/psemek/geom/intersection.hpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/libs/geom/include/psemek/geom/intersection.hpp b/libs/geom/include/psemek/geom/intersection.hpp
index 5224e0a6..100b8702 100644
--- a/libs/geom/include/psemek/geom/intersection.hpp
+++ b/libs/geom/include/psemek/geom/intersection.hpp
@@ -211,6 +211,25 @@ namespace psemek::geom
 		return static_cast<bool>(intersection(seg, s));
 	}
 
+	template <typename T, std::size_t N>
+	interval<T> intersection(segment<point<T, N>> const & seg, sphere<T, N> const & s)
+	{
+		auto d = seg[0] - s.center;
+		auto dir = seg[1] - seg[0];
+
+		auto ir = solve_quadratic(length_sqr(dir), T{2} * dot(dir, d), length_sqr(d) - sqr(s.radius));
+		if (!ir)
+			return {};
+
+		return {std::max(T{0}, ir->first), std::min(T{1}, ir->second)};
+	}
+
+	template <typename T, std::size_t N>
+	bool intersect(segment<point<T, N>> const & seg, sphere<T, N> const & s)
+	{
+		return !intersection(seg, s).empty();
+	}
+
 	template <typename T, std::size_t N>
 	interval<T> intersection(ray<T, N> const & r, sphere<T, N> const & s)
 	{