From 7fed55840f8482f8aa961f06f3f8f5b5af2d85c1 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 16 Oct 2014 00:04:53 +0300
Subject: [PATCH] Add an empty flag to BoundingSphere

Useful for distinguishing a bounding sphere that has nothing in it from
one that contains a single point.
---
 source/geometry/boundingsphere.h | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/source/geometry/boundingsphere.h b/source/geometry/boundingsphere.h
index 40826ca..dd20d96 100644
--- a/source/geometry/boundingsphere.h
+++ b/source/geometry/boundingsphere.h
@@ -13,9 +13,10 @@ class BoundingSphere
 private:
 	LinAl::Vector<T, N> center;
 	T radius;
+	bool empty;
 
 public:
-	BoundingSphere(): radius(0) { }
+	BoundingSphere();
 	BoundingSphere(const LinAl::Vector<T, N> &, T);
 
 	template<typename Iter>
@@ -23,12 +24,20 @@ public:
 
 	const LinAl::Vector<T, N> get_center() const { return center; }
 	T get_radius() const { return radius; }
+	bool is_empty() const { return empty; }
 };
 
+template<typename T, unsigned N>
+BoundingSphere<T, N>::BoundingSphere():
+	radius(0),
+	empty(true)
+{ }
+
 template<typename T, unsigned N>
 BoundingSphere<T, N>::BoundingSphere(const LinAl::Vector<T, N> &c, T r):
 	center(c),
-	radius(r)
+	radius(r),
+	empty(false)
 { }
 
 template<typename T, unsigned N>
@@ -37,6 +46,9 @@ BoundingSphere<T, N> BoundingSphere<T, N>::from_point_cloud(const Iter &begin, c
 {
 	using std::sqrt;
 
+	if(begin==end)
+		return BoundingSphere<T, N>();
+
 	LinAl::Vector<T, N> p1;
 	T sqdist = 0;
 	for(Iter i=begin; i!=end; ++i)
@@ -83,6 +95,11 @@ BoundingSphere<T, N> BoundingSphere<T, N>::from_point_cloud(const Iter &begin, c
 template<typename T, unsigned N>
 BoundingSphere<T, N> operator|(const BoundingSphere<T, N> &bs1, const BoundingSphere<T, N> &bs2)
 {
+	if(bs1.is_empty())
+		return bs2;
+	else if(bs2.is_empty())
+		return bs1;
+
 	LinAl::Vector<T, N> v = bs2.get_center()-bs1.get_center();
 	T d = v.norm();
 	if(d+bs2.get_radius()<bs1.get_radius())
-- 
2.43.0