Account for UV coordinate flip in UVController (Fixes #3203)

components/nifosg/controller.cpp

@@ -254,9 +254,15 @@ void UVController::apply(osg::StateSet* stateset, osg::NodeVisitor* nv)
         float uScale = mUScale.interpKey(value);
         float vScale = mVScale.interpKey(value);
 
+        osg::Matrix flipMat;
+        flipMat.preMultTranslate(osg::Vec3f(0,1,0));
+        flipMat.preMultScale(osg::Vec3f(1,-1,1));
+
         osg::Matrixf mat = osg::Matrixf::scale(uScale, vScale, 1);
         mat.setTrans(uTrans, vTrans, 0);
 
+        mat = flipMat * mat * flipMat;
+
         // setting once is enough because all other texture units share the same TexMat (see setDefaults).
         if (!mTextureUnits.empty())
         {