Pass a Vec4f by reference

components/sceneutil/lightcontroller.cpp

@@ -125,7 +125,7 @@ namespace SceneUtil
         traverse(node, nv);
     }
 
-    void LightController::setDiffuse(osg::Vec4f color)
+    void LightController::setDiffuse(const osg::Vec4f& color)
     {
         mDiffuseColor = color;
     }

components/sceneutil/lightcontroller.hpp

@@ -24,7 +24,7 @@ namespace SceneUtil
 
         void setType(LightType type);
 
-        void setDiffuse(osg::Vec4f color);
+        void setDiffuse(const osg::Vec4f& color);
 
         virtual void operator()(osg::Node* node, osg::NodeVisitor* nv);