From 4f802689f23456e7db7920aeb690516b7a3f399e Mon Sep 17 00:00:00 2001
From: frohlich <frohlich>
Date: Wed, 16 Sep 2009 05:06:56 +0000
Subject: [PATCH] Correct finite precision issues. Use consistent function
 names. Implement changes consistently over the different vector sizes.

Modified Files:
	SGVec2.hxx SGVec3.hxx SGVec4.hxx
---
 simgear/math/SGVec2.hxx | 19 ++++++++++++++++++-
 simgear/math/SGVec3.hxx | 29 +++++++++++++++++------------
 simgear/math/SGVec4.hxx | 19 ++++++++++++++++++-
 3 files changed, 53 insertions(+), 14 deletions(-)

diff --git a/simgear/math/SGVec2.hxx b/simgear/math/SGVec2.hxx
index 5024e2c1..65c802ea 100644
--- a/simgear/math/SGVec2.hxx
+++ b/simgear/math/SGVec2.hxx
@@ -244,7 +244,12 @@ template<typename T>
 inline
 SGVec2<T>
 normalize(const SGVec2<T>& v)
-{ return (1/norm(v))*v; }
+{
+  T normv = norm(v);
+  if (normv <= SGLimits<T>::min())
+    return SGVec2<T>::zeros();
+  return (1/normv)*v;
+}
 
 /// Return true if exactly the same
 template<typename T>
@@ -331,6 +336,18 @@ T
 distSqr(const SGVec2<T>& v1, const SGVec2<T>& v2)
 { SGVec2<T> tmp = v1 - v2; return dot(tmp, tmp); }
 
+// calculate the projection of u along the direction of d.
+template<typename T>
+inline
+SGVec2<T>
+projection(const SGVec2<T>& u, const SGVec2<T>& d)
+{
+  T denom = dot(d, d);
+  T ud = dot(u, d);
+  if (SGLimits<T>::min() < denom) return u;
+  else return d * (dot(u, d) / denom);
+}
+
 #ifndef NDEBUG
 template<typename T>
 inline
diff --git a/simgear/math/SGVec3.hxx b/simgear/math/SGVec3.hxx
index 9b81ec57..64ceac0a 100644
--- a/simgear/math/SGVec3.hxx
+++ b/simgear/math/SGVec3.hxx
@@ -358,9 +358,11 @@ template<typename T>
 inline
 SGVec3<T>
 normalize(const SGVec3<T>& v)
-{ T normv = norm(v);
-  if (normv > 0.0) return (1/norm(v))*v;
-  else return v;
+{
+  T normv = norm(v);
+  if (normv <= SGLimits<T>::min())
+    return SGVec3<T>::zeros();
+  return (1/normv)*v;
 }
 
 /// Return true if exactly the same
@@ -452,6 +454,18 @@ T
 distSqr(const SGVec3<T>& v1, const SGVec3<T>& v2)
 { SGVec3<T> tmp = v1 - v2; return dot(tmp, tmp); }
 
+// calculate the projection of u along the direction of d.
+template<typename T>
+inline
+SGVec3<T>
+projection(const SGVec3<T>& u, const SGVec3<T>& d)
+{
+  T denom = dot(d, d);
+  T ud = dot(u, d);
+  if (SGLimits<T>::min() < denom) return u;
+  else return d * (dot(u, d) / denom);
+}
+
 #ifndef NDEBUG
 template<typename T>
 inline
@@ -480,15 +494,6 @@ SGVec3d
 toVec3d(const SGVec3f& v)
 { return SGVec3d(v(0), v(1), v(2)); }
 
-// calculate the projection of u along the direction of d.
-template<typename T>
-inline SGVec3<T> SGProjection(const SGVec3<T>& u, const SGVec3<T>& d)
-{
-  T denom = dot(d, d);
-  if (denom == 0.) return u;
-  else return  d * (dot(u,d) / denom);
-}
-
 #ifndef NO_OPENSCENEGRAPH_INTERFACE
 inline
 SGVec3d
diff --git a/simgear/math/SGVec4.hxx b/simgear/math/SGVec4.hxx
index baf9137d..6030c48b 100644
--- a/simgear/math/SGVec4.hxx
+++ b/simgear/math/SGVec4.hxx
@@ -288,7 +288,12 @@ template<typename T>
 inline
 SGVec4<T>
 normalize(const SGVec4<T>& v)
-{ return (1/norm(v))*v; }
+{
+  T normv = norm(v);
+  if (normv <= SGLimits<T>::min())
+    return SGVec4<T>::zeros();
+  return (1/normv)*v;
+}
 
 /// Return true if exactly the same
 template<typename T>
@@ -383,6 +388,18 @@ T
 distSqr(const SGVec4<T>& v1, const SGVec4<T>& v2)
 { SGVec4<T> tmp = v1 - v2; return dot(tmp, tmp); }
 
+// calculate the projection of u along the direction of d.
+template<typename T>
+inline
+SGVec4<T>
+projection(const SGVec4<T>& u, const SGVec4<T>& d)
+{
+  T denom = dot(d, d);
+  T ud = dot(u, d);
+  if (SGLimits<T>::min() < denom) return u;
+  else return d * (dot(u, d) / denom);
+}
+
 #ifndef NDEBUG
 template<typename T>
 inline
-- 
2.39.5