Flipping one textured face of an object I came up with a problem of flipping only one face of the texture horizontally on flags as shown below in the image. What I want to do is to make one (front) face of the flag stay as it is now, but I would like to flip the other (rear face) by 180 degrees. I tried playing with the scale factors in the mapping node, rotating that face etc. The problem is that I am aware of the potential solution to this problem by duplicating the face and flipping the normals, but it will just make my job a lot harder due to complexity of the model and a huge lag I am currently experiencing. I would have to repeat the process a lot of times too. Therefore I would like to do it via compositor. I made a composition as shown on the screenshot, but it doesn't work no matter how I make them and what factors I put in. Can anyone take a look at it please, and tell me if I am doing something wrong, or it just isn't possible to be achieved in this way.

 

Thank you very much in advance.
Use UV coordinates instead of normal.  Then unwrap the flag with  u > unwrap.  Then in the UV image editor, while still in edit mode, scale the UV map along the horizontal axis by -1:  s > x > -1.  Scaling by -1 should flip the image.

Update:  Misunderstood the question.  I modified your node setup. This should make an un-flipped image appear on the back of the face.