X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=simgear%2Fmath%2FSGVec4.hxx;h=6030c48ba03e2ea331b43442cebfd2df509fdf1b;hb=11479cd8c386d8bf7e1fee7bed60ab4abefc5fad;hp=baf9137daa2aba31e290c5c81a022f72d2254847;hpb=9cbbe5559844317f44744788ddb308101a1e75e9;p=simgear.git

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