From 3a3c1fd8e854b99289c92ea2074b56f4fe294f53 Mon Sep 17 00:00:00 2001
From: boromisp <peti.boromissza@gmail.com>
Date: Sun, 11 Nov 2012 23:09:12 +0100
Subject: [PATCH] Added new ray-sphere intersection

This version uses a geometric method (usually faster) and doesn't
calculate the intersection position and normal, only the distance.
---
 glm/gtx/intersect.hpp |  9 +++++++++
 glm/gtx/intersect.inl | 21 +++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/glm/gtx/intersect.hpp b/glm/gtx/intersect.hpp
index 1c090b67..a997555c 100644
--- a/glm/gtx/intersect.hpp
+++ b/glm/gtx/intersect.hpp
@@ -68,6 +68,15 @@ namespace glm
 		genType const & vert0, genType const & vert1, genType const & vert2,
 		genType & position);
 
+	//! Compute the intersection distance of a ray and a sphere. 
+	//! The ray direction vector is unit length.
+	//! From GLM_GTX_intersect extension.
+	template <typename genType>
+	bool intersectRaySphere(
+		genType const & rayStarting, genType const & rayNormalizedDirection,
+		genType const & sphereCenter, const typename genType::value_type sphereRadiusSquered,
+		typename genType::value_type & intersectionDistance);
+
     //! Compute the intersection of a ray and a sphere.
 	//! From GLM_GTX_intersect extension.
 	template <typename genType>
diff --git a/glm/gtx/intersect.inl b/glm/gtx/intersect.inl
index ad55837f..89e18886 100644
--- a/glm/gtx/intersect.inl
+++ b/glm/gtx/intersect.inl
@@ -127,6 +127,27 @@ namespace glm
 		return true;
 	}
 
+	template <typename genType>
+	GLM_FUNC_QUALIFIER bool intersectRaySphere
+	(
+		genType const & rayStarting, genType const & rayNormalizedDirection,
+		genType const & sphereCenter, const typename genType::value_type sphereRadiusSquered,
+		typename genType::value_type & intersectionDistance
+	)
+	{
+		typename genType::value_type Epsilon = std::numeric_limits<typename genType::value_type>::epsilon();
+		genType diff = sphereCenter - rayStarting;
+		typename genType::value_type t0 = dot(diff, rayNormalizedDirection);
+		typename genType::value_type dSquared = dot(diff, diff) - t0 * t0;
+		if( dSquared > sphereRadiusSquered )
+		{
+			return false;
+		}
+		typename genType::value_type t1 = sqrt( sphereRadiusSquered - dSquared );
+		intersectionDistance = t0 > t1 + Epsilon ? t0 - t1 : t0 + t1;
+		return intersectionDistance > Epsilon;
+	}
+
 	template <typename genType>
 	GLM_FUNC_QUALIFIER bool intersectRaySphere
 	(