Direct3D header update.

diff --git a/include/d3dvec.inl b/include/d3dvec.inl
index 03dc5f5..6621b9e 100644
--- a/include/d3dvec.inl
+++ b/include/d3dvec.inl
@@ -51,6 +51,18 @@
   return *this;
 }
 
+/*** unary operators ***/
+
+inline _D3DVECTOR operator + (const _D3DVECTOR& v)
+{
+  return v;
+}
+
+inline _D3DVECTOR operator - (const _D3DVECTOR& v)
+{
+  return _D3DVECTOR(-v.x, -v.y, -v.z);
+}
+
 /*** binary operators ***/
 
 inline _D3DVECTOR operator + (const _D3DVECTOR& v1, const _D3DVECTOR& v2)