From e0312b66b1fa45eb0af75c2ee04ba733e5f54908 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 23 Dec 2021 10:56:58 +0300
Subject: [PATCH] Fix ray-sphere intersection: return an interval

---
 libs/geom/include/psemek/geom/intersection.hpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libs/geom/include/psemek/geom/intersection.hpp b/libs/geom/include/psemek/geom/intersection.hpp
index dc8d8324..3a697e8f 100644
--- a/libs/geom/include/psemek/geom/intersection.hpp
+++ b/libs/geom/include/psemek/geom/intersection.hpp
@@ -211,17 +211,21 @@ namespace psemek::geom
 	}
 
 	template <typename T, std::size_t N>
-	std::optional<std::pair<T, T>> intersection(ray<T, N> const & r, sphere<T, N> const & s)
+	interval<T> intersection(ray<T, N> const & r, sphere<T, N> const & s)
 	{
 		auto d = r.origin - s.center;
 
-		return solve_quadratic(length_sqr(r.direction), T{2} * dot(r.direction, d), length_sqr(d) - sqr(s.radius));
+		auto ir = solve_quadratic(length_sqr(r.direction), T{2} * dot(r.direction, d), length_sqr(d) - sqr(s.radius));
+		if (!ir)
+			return {};
+
+		return {ir->first, ir->second};
 	}
 
-	template <typename T, std::size_t N, typename = std::enable_if_t<(N > 2)>>
+	template <typename T, std::size_t N>
 	bool intersect(ray<T, N> const & r, sphere<T, N> const & s)
 	{
-		return static_cast<bool>(intersection(r, s));
+		return intersection(r, s).empty();
 	}
 
 }